subject:"Re\: \[OSM\-talk\] Divided roads proposal"

On Sat, Dec 5, 2009 at 1:43 AM, Anthony o...@inbox.org wrote:
1, 2. Dual carriageway

 5, 6, 7, 8, 9, 10. Dual carriageway


Alright, but let's be practical. It's a lot of effort to create and maintain
pairs of roads (let's not call them dual carriageways - that's really a
specific type of motorway). Let's imagine this tag is implemented and there
is renderer support. What value do you see in mapping examples 2 and 10 as
pairs of roads rather than a single road with divided=median?

Is the benefit just so you can get more precise with area micromapping?
Let's assume, because it's true, that volunteer mapping time is limited, and
the use of areas to micromap roads is rare, and certainly not expected by
end users. Why is a pair of roads better in 2 than a single, divided road?

Steve
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Re: [OSM-talk] Divided roads proposal

Steve Bennett wrote:
 On Sat, Dec 5, 2009 at 1:43 AM, Anthony o...@inbox.org 
 mailto:o...@inbox.org wrote:
  1, 2. Dual carriageway
 
 5, 6, 7, 8, 9, 10. Dual carriageway
 
 
 Alright, but let's be practical. It's a lot of effort to create and 
 maintain pairs of roads (let's not call them dual carriageways - 
 that's really a specific type of motorway). Let's imagine this tag is 
 implemented and there is renderer support. What value do you see in 
 mapping examples 2 and 10 as pairs of roads rather than a single road 
 with divided=median?
 
 Is the benefit just so you can get more precise with area micromapping? 
 Let's assume, because it's true, that volunteer mapping time is limited, 
 and the use of areas to micromap roads is rare, and certainly not 
 expected by end users. Why is a pair of roads better in 2 than a single, 
 divided road?

Many of the example pictures have end cases that need to be handled by 
separated 
roads, so why not just draw the reality on the ground? Having to add MORE 
complexity such as you can turn off this side of the road is just as wrong? So 
map the dual carriage way section, and show the other detail joining to the 
physical situation?

In many areas, the macro level view is complete and people are starting to look 
at the micro view. Just because a few areas 'might look better' in the macro 
view is no reason to remove the existing format, and I see little point adding 
tags for something that is hiding the micro view?

SOME roads do need a 'divider' tag, but only to add 'white line' and other 
'micro' data that can't be included by areas or other means. The crosshatch 
area 
is just another edge case that needs to be handled in bother levels.

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Re: [OSM-talk] Divided roads proposal

On Sun, Dec 6, 2009 at 10:43 PM, Lester Caine les...@lsces.co.uk wrote:

 Many of the example pictures have end cases that need to be handled by
 separated
 roads, so why not just draw the reality on the ground?


Because, as someone else pointed out, drawing the reality on the ground
isn't the only, or even, best approach for mapping. The slightly more
abstract this is a single road, divided works better than this is two
roads in some cases.

It seems to me that to almost any proposal you could argue why not just
draw the reality on the ground?:
Q: Can we have a cinema tag?
A: Why not just draw the reality on the ground? It's a building, with
chairs, a room with a projector...

Q: Can we have a swimming pool tag?
A: Why not just draw the reality on the ground? It's a waterway,
surface=tiles, foot=yes, bicycle=no...



 Having to add MORE
 complexity such as you can turn off this side of the road is just as wrong?


I don't think a single road with a single junction leading to a side road,
with a single tag, could possibly be construed as more complex than two
roads with an extra road for the gap.


 In many areas, the macro level view is complete and people are starting to
 look
 at the micro view. Just because a few areas 'might look better' in the
 macro
 view is no reason to remove the existing format,


I repeat: I am not proposing removing anything.

I'm proposing *adding* a tag, primarily to allow *adding* information about
*new* streets. It's possible this will mean that some streets that *would
have* been mapped as two roads will instead be mapped as one road, but it's
a stretch to call that removing anything.

(Sorry for the irritated tone, but...c'mon.)




 and I see little point adding
 tags for something that is hiding the micro view?


If and when roads are mapped as areas (in addition to ways), I'm sure you'll
be able to map the individual halves of the divided road to your heart's
content. Just like you'll be able to map every lane, every slipway, every
traffic island and every painted arrow.

Honestly though, the primary function of OSM is not the micro view. We're
not primarily interested in centimetre perfect placement of lumps of
concrete. Are you really suggesting that we don't use a feature because it
might interfere with the micro view, even though it works better at the
macro view?

Steve
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Re: [OSM-talk] Divided roads proposal

Steve Bennett wrote:
 Honestly though, the primary function of OSM is not the micro view. 
 We're not primarily interested in centimetre perfect placement of lumps 
 of concrete. Are you really suggesting that we don't use a feature 
 because it might interfere with the micro view, even though it works 
 better at the macro view?

Why do you say THAT ?
Many of the additions currently being discussed ARE because the macro view is 
now complete, and adding the fine detail is now being carried out. There is no 
PRIMARY interest. Everybody has their own views on what is important!

I think my only problem with 'divided' is At what point do you apply it? The 
samples being shown are quite clearly - on the whole - dual carriageway 
structures. Example 10 clearly has a more complex structure than can be mapped 
by showing a 'divided' tag, since there is no access to the joining road from 
the other carriageway?

Example 6 has some quite complex slip roads that really need isolated ways for 
the main carriageway. Trying to ADD tags to supplement a simple 'divided' tag 
to 
explain the slips on and off at the end is handled much easier with a simple 
dual carriage way? And many of the other examples need the same end cases. So 
at 
what level does a simple 'divided' tag actually work in practice? However 
'double white lines' on a single carriage way road IS a divider that needs 
tagging?

-- 
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Re: [OSM-talk] Divided roads proposal

On Mon, Dec 7, 2009 at 12:30 AM, Lester Caine les...@lsces.co.uk wrote:

 I think my only problem with 'divided' is At what point do you apply it?
 The
 samples being shown are quite clearly - on the whole - dual carriageway
 structures.


(Just on terminology, I'm used to dual carriageway only being applied to
motorways, but Wikipedia says it technically applies to any road. We'll go
with that, then, ok.)

By are clearly dual carriageway structures, I take it you're
distinguishing between roads which have a shortish traffic island of some
type, versus those which are divided for a long stretch. Is this important?

Example 10 clearly has a more complex structure than can be mapped
 by showing a 'divided' tag, since there is no access to the joining road
 from
 the other carriageway?


Have you read the proposal?

http://wiki.openstreetmap.org/wiki/Proposed_features/Divided_road

It covers *exactly* this case. In my proposal (ie, not Vovanium's, which
cohabits the page),  when there's a junction (like the road entering from
SW), by default that road can't cross the median - there is no gap. You can
see how this looks in my mocked up Halcyon image.



 Example 6 has some quite complex slip roads that really need isolated ways
 for
 the main carriageway. Trying to ADD tags to supplement a simple 'divided'
 tag to
 explain the slips on and off at the end is handled much easier with a
 simple
 dual carriage way?


Do slip ways need to be modelled at all? At the moment, they're not, as far
as I have seen. Essentially what is going on at that intersection is very
straight forward: divided road meets (temporarily) divided road, and all
turns are possible. Currently, I don't think many people would map the N/S
as divided (ie, two ways). With this proposal, you could do so, without
creating a mess.


 And many of the other examples need the same end cases. So at
 what level does a simple 'divided' tag actually work in practice? However


IMHO, the divided tag is well suited to all cases except 6, 7, and 9. Number
2 in particular is a perfect example. Worth tagging, not worth splitting the
road in two for.


 'double white lines' on a single carriage way road IS a divider that needs
 tagging?


Yeah, I deliberated over whether or not to include that. What do you think -
same proposal, or separate? Double white lines really aren't a divider,
they're a restriction on overtaking.

Steve
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Re: [OSM-talk] Divided roads proposal

2009-12-06 Thread Anthony

On Sun, Dec 6, 2009 at 5:55 AM, Steve Bennett stevag...@gmail.com wrote:

 On Sat, Dec 5, 2009 at 1:43 AM, Anthony o...@inbox.org wrote:
 1, 2. Dual carriageway

 5, 6, 7, 8, 9, 10. Dual carriageway


 Alright, but let's be practical. It's a lot of effort to create and
 maintain pairs of roads (let's not call them dual carriageways - that's
 really a specific type of motorway). Let's imagine this tag is implemented
 and there is renderer support. What value do you see in mapping examples 2
 and 10 as pairs of roads rather than a single road with divided=median?

 Is the benefit just so you can get more precise with area micromapping?
 Let's assume, because it's true, that volunteer mapping time is limited, and
 the use of areas to micromap roads is rare, and certainly not expected by
 end users. Why is a pair of roads better in 2 than a single, divided road?


If you don't see how it's more accurate, I can't help you.

Yes, in many of those cases you outline, it's overkill.  But in those same
cases, just leaving a single way and not worrying about the divider at all
is fine.  Only in a case where the divider provides routing information
(other than the ability to U-turn) would I say that it's important to use a
dual carriageway (seems to me to fit the dictionary definition).  The
divided=median tag is already micromapping.  All I'm saying is if you're
going to start micromapping, do it right.

OTOH, if you don't intend to use divided=* to represent routing information,
so routers and renderers can safely ignore the tag, then do whatever you
want with it.  Like I suggested, I'll just treat it as a type of todo tag.
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Re: [OSM-talk] Divided roads proposal

On Mon, Dec 7, 2009 at 1:03 AM, Anthony o...@inbox.org wrote:

 Is the benefit just so you can get more precise with area micromapping?
 Let's assume, because it's true, that volunteer mapping time is limited, and
 the use of areas to micromap roads is rare, and certainly not expected by
 end users. Why is a pair of roads better in 2 than a single, divided road?


 If you don't see how it's more accurate, I can't help you.


I said better. You say accurate, but you probably mean precise.

Let's say I ask you the time. You reply Sun Dec  6 06:11:07 2009 PST. A
better answer would have been ten past one AM.

I can understand your temptation to think that increasing levels of
precision are always better: usually it is. But the problem here is:
1) The extra precision of precisely mapping two ways means extra complexity,
hence more difficulty in rendering, and it maps less well onto the user's
mental model. Just like amenity=swimming_pool is better, if less precise,
than a natural=water, with precise details of surface materials and whatnot.
2) Extra precision requires more information, which we don't necessarily
have. How would you map a divided road which you don't have an aerial photo
for? You have a GPS trace with points every 10 metres, with an accuracy of
about 5 metres. How would you map this: two ways? Now you see the difference
between precision and accuracy: you have precisely mapped out two ways, when
in fact neither is particularly accurate.
3) Extra precision requires more time, which we don't necessarily have.
Let's say that we agree that all divided roads should be mapped as two
ways. Let's also say it takes on average 1 minute to trace out a single way.
There's a volunteer with 60 divided roads to map in front of him, and he's
got one hour to spend. See where I'm going?


 Yes, in many of those cases you outline, it's overkill.  But in those same
 cases, just leaving a single way and not worrying about the divider at all
 is fine.


Absolutely. We agree on two situations:

1) Roads with a division too trivial to map, which we map as a single way.

3) Large, dual-carriage roads with a division too complex to model with a
simple divided=* tag, which we map as two separate ways.

Can you guess what number 2) is?


 Only in a case where the divider provides routing information (other than
 the ability to U-turn) would I say that it's important to use a dual
 carriageway (seems to me to fit the dictionary definition).  The
 divided=median tag is already micromapping.


I disagree, but I accept that the line of what is considered to be
micromapping is subjective. You explain very well the current conundrum:
there are currently only two choices, either map out the division as two
separate roads (a dual carriageway), or declare it micromapping and
ignore it. I'm proposing a third choice, that lets you capture some useful
information without the overhead of the dual carriageway.


 All I'm saying is if you're going to start micromapping, do it right.


This is the most compelling argument against my proposal, and I'm surprised
no one has brought it up yet: the divider=* tag can be used for certain
kinds of traffic islands (namely those that run down the middle of a two way
road), but not others (such as slipway dividers, islands in one way streets,
islands in intersections...)

However, I think do it right is an immense, open-ended, complex task. This
proposal addreses enough common situations that it's worth implementing,
even if we still can't map *everything*.



 OTOH, if you don't intend to use divided=* to represent routing
 information, so routers and renderers can safely ignore the tag, then do
 whatever you want with it.  Like I suggested, I'll just treat it as a type
 of todo tag.


I suggest you read the Routing section of the proposal.
Steve
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Re: [OSM-talk] Divided roads proposal

Steve Bennett wrote:
 On Mon, Dec 7, 2009 at 12:30 AM, Lester Caine les...@lsces.co.uk 
 mailto:les...@lsces.co.uk wrote:
 
 I think my only problem with 'divided' is At what point do you
 apply it? The
 samples being shown are quite clearly - on the whole - dual carriageway
 structures. 
 
 (Just on terminology, I'm used to dual carriageway only being applied 
 to motorways, but Wikipedia says it technically applies to any road. 
 We'll go with that, then, ok.)

MANY major routes in the UK are trunk roads and most routes around cities will 
have one way elements that split and join at different points. YES it is the 
A?? 
and a single name, but the structure can only be mapped as a dual carriage way. 
Which then takes us to some of the 'green way' areas where cars go down either 
side of a grass verge. A simple 'divided' in your tag, but the separation may 
grow from nothing to several meters. At what point do you change from 'divided' 
to separate ways, which then begs the question - why have divided if it's just 
a 
  shorthand for two ways with opposite directions.

 By are clearly dual carriageway structures, I take it you're 
 distinguishing between roads which have a shortish traffic island of 
 some type, versus those which are divided for a long stretch. Is this 
 important?
 
 Example 10 clearly has a more complex structure than can be mapped
 by showing a 'divided' tag, since there is no access to the joining
 road from
 the other carriageway?
 
 Have you read the proposal?
 http://wiki.openstreetmap.org/wiki/Proposed_features/Divided_road

You need to justify the real need for it. I'll continue to map the actual 
structure, and add the additional ways for the related footpaths. I don't see 
the need for this shorthand for many of the cases you are trying to make?

 It covers *exactly* this case. In my proposal (ie, not Vovanium's, which 
 cohabits the page),  when there's a junction (like the road entering 
 from SW), by default that road can't cross the median - there is no gap. 
 You can see how this looks in my mocked up Halcyon image.

I think what YOU are missing is that in most cases where there are traffic 
islands which add one way sections of way, they ARE mapped. Around here there 
was an attempted to remove some of them, but that has been rolled back, so 
where 
a road splits, the correct direction ways are added. Routing does not then need 
to run through lots of additional tags to find if it can then do a maneuver ...

 Example 6 has some quite complex slip roads that really need
 isolated ways for
 the main carriageway. Trying to ADD tags to supplement a simple
 'divided' tag to
 explain the slips on and off at the end is handled much easier with
 a simple
 dual carriage way? 
 
 Do slip ways need to be modelled at all? At the moment, they're not, as 
 far as I have seen. Essentially what is going on at that intersection is 
 very straight forward: divided road meets (temporarily) divided road, 
 and all turns are possible. Currently, I don't think many people would 
 map the N/S as divided (ie, two ways). With this proposal, you could do 
 so, without creating a mess.

I think it is essential that slipways are mapped. ESPECIALLY when one is trying 
to add the right routing instructions. TomTom has started showing motorway and 
major road slipway details properly. You need to know when to get to an inside 
lane and take a slip road PRIOR to the actual junction. These are no different 
to the island details approaching a roundabout, so trying to 'save time' by not 
actually adding quite important detail does seem wrong? A tag saying you should 
have taken the slip 10 mts before this junction is not sensible.

 And many of the other examples need the same end cases. So at
 what level does a simple 'divided' tag actually work in practice?
 However
 
 IMHO, the divided tag is well suited to all cases except 6, 7, and 9. 
 Number 2 in particular is a perfect example. Worth tagging, not worth 
 splitting the road in two for.
 
 'double white lines' on a single carriage way road IS a divider that
 needs tagging?
 
 Yeah, I deliberated over whether or not to include that. What do you 
 think - same proposal, or separate? Double white lines really aren't a 
 divider, they're a restriction on overtaking.

Example 3 is no more than a wide 'double line' road marking. SO is it a 
'divided' or is it simply a road marking? The problem with the proposal is that 
it does not have any indication on when it should be used ... or when the more 
detailed current methods are actually more appropriate?

-- 
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-
Contact - http://lsces.co.uk/wiki/?page=contact
L.S.Caine Electronic Services - http://lsces.co.uk
EnquirySolve - http://enquirysolve.com/
Model Engineers Digital Workshop - http://medw.co.uk//
Firebird - http://www.firebirdsql.org/index.php

Re: [OSM-talk] Divided roads proposal

2009-12-06 Thread Richard Bullock

 3) Extra precision requires more time, which we don't necessarily have.
 Let's say that we agree that all divided roads should be mapped as two
 ways. Let's also say it takes on average 1 minute to trace out a single 
 way.
 There's a volunteer with 60 divided roads to map in front of him, and he's
 got one hour to spend. See where I'm going?

And you don't have to do all 60 dual carriageways in one sitting.

But to be completely honest, mapping out dual carriageways is really not 
*that* time consuming. In JOSM you could just copy the way you have drawn 
and drag the copied way a few metres to the side and reverse the direction. 
You'd then have to connect up side roads and tweak a few nodes - but should 
take no more than a couple of seconds if you can't be bothered drawing out 
the other carriageway. I'm sure Potlatch probably has a similar feature.

And in a world with a large but finite number of roads, where a relatively 
small fraction of roads are dual carriageway, and an ever increasing army of 
mappers - it's really not that bad.








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Re: [OSM-talk] Divided roads proposal

On Mon, Dec 7, 2009 at 4:11 AM, Richard Bullock rb...@cantab.net wrote:

 But to be completely honest, mapping out dual carriageways is really not
 *that* time consuming. In JOSM you could just copy the way you have drawn
 and drag the copied way a few metres to the side and reverse the direction.


If that's the case, it sort of shoots down the dual carriageway contains
more information than a single way argument, doesn't it?


 You'd then have to connect up side roads and tweak a few nodes - but should
 take no more than a couple of seconds if you can't be bothered drawing out
 the other carriageway. I'm sure Potlatch probably has a similar feature.


I'm not sure it does.

And in a world with a large but finite number of roads, where a relatively
 small fraction of roads are dual carriageway, and an ever increasing army
 of
 mappers - it's really not that bad.


Speaking for myself, what motivated my interest in this is that it is
tedious, and doesn't feel like the right thing to be doing. These minor
roads don't seem like they deserve too complete roads. Google Maps maps them
as single roads. Melway maps them as a single road which renders like a
double road (ie, variations in median width aren't accounted for). Yahoo —
now that I look — does exactly what I'm proposing, rendering a single road
with a dotted line down the middle to indicate the division.  Now, I don't
know what weight what everyone else is doing carries, but it indicates
something.

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Re: [OSM-talk] Divided roads proposal

On Mon, Dec 7, 2009 at 2:31 AM, Lester Caine les...@lsces.co.uk wrote:

 grow from nothing to several meters. At what point do you change from
 'divided'
 to separate ways, which then begs the question


This is the same kind of question as when a road switches from tertiary to
secondary etc. Does it need a firm answer? It would only be problematic,
IMHO, if a road was frequently switching from one form to the other.


 - why have divided if it's just a
  shorthand for two ways with opposite directions.


I don't think it is just a shorthand. In many cases I would put it the
other way: two ways with opposite directions is just a kludge for a
single divided road. Up until now, we haven't had a way to properly tag a
single divided road, so we do it with two ways. We can fix that.


  You need to justify the real need for it. I'll continue to map the actual
 structure, and add the additional ways for the related footpaths. I don't
 see
 the need for this shorthand for many of the cases you are trying to make?


If you're mapping every footpath, you are clearly working at a different
level of detail. It's great that your area apparently has every road already
covered already. Mine doesn't.

To put it differently, the real need is to be able to efficiciently map
areas which have divided roads, without resorting to micromapping them as
two ways. I understand that you wouldn't use this tag. But would you object
to others using it?



 I think what YOU are missing is that in most cases where there are traffic
 islands which add one way sections of way, they ARE mapped. Around here
 there


Yes. And does mapping a traffic island as a splitting of a road into two
ways not scream wrong! at you?

Example:
http://www.openstreetmap.org/?lat=-37.820693lon=144.919989zoom=18layers=B000FTF

This looks right to you?


 was an attempted to remove some of them, but that has been rolled back, so
 where
 a road splits, the correct direction ways are added. Routing does not then
 need
 to run through lots of additional tags to find if it can then do a maneuver
 ...


One key for ways, one key for junctions. Trivial stuff.



 I think it is essential that slipways are mapped. ESPECIALLY when one is
 trying
 to add the right routing instructions. TomTom has started showing motorway
 and
 major road slipway details properly. You need to know when to get to an
 inside
 lane and take a slip road PRIOR to the actual junction.


Maybe we should be mapping slipways, hopefully there's a better approach
than marking them all as fully fledged roads though.


 These are no different
 to the island details approaching a roundabout, so trying to 'save time' by
 not
 actually adding quite important detail does seem wrong?


Even if it were the case that this was important detail which I was
proposing not adding, it wouldn't be wrong, because surely a slipway here
is not as important as a whole road not mapped somewhere else.


 Example 3 is no more than a wide 'double line' road marking. SO is it a
 'divided' or is it simply a road marking?


Either way, we currently have no way of marking it.


 The problem with the proposal is that
 it does not have any indication on when it should be used ...


Other than, say,
http://wiki.openstreetmap.org/wiki/Proposed_features/Divided_road#Scope

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Re: [OSM-talk] Divided roads proposal

2009-12-06 Thread Richard Bullock

But to be completely honest, mapping out dual carriageways is really not
*that* time consuming. In JOSM you could just copy the way you have drawn
and drag the copied way a few metres to the side and reverse the 
direction.

If that's the case, it sort of shoots down the dual carriageway contains 
more
information than a single way argument, doesn't it?

Speaking for myself, what motivated my interest in this is that it is 
tedious, and doesn't
feel like the right thing to be doing. These minor roads don't seem like 
they deserve too complete roads

No, it doesn't shoot down the argument. I just said it was an option if you 
couldn't be bothered to map it properly. And really, it doesn't take long 
anyway. And your proposed scheme for routing makes your scheme more 
complicated for the routers than mapping as two ways. In the existing 
scheme, if a shared node is not present between two ways, no routing is 
possible directly between the two. This is true regardless of what routing 
software you are using - it doesn't require extra tags or fudges to make 
it work. And think for a minute that there might be external data users who 
might not know to update their routing software for these extra tags. And 
not knowing about physically impossible turns is worse than not knowing 
about legal restrictions (turn restrictions).

I can't disagree more about minor roads not deserving to be mapped fully. 
We should map everything to the best of our abilities. And given the 
community we have, I'm sure someone will sooner or later - even if you find 
it 'tedious'. Some people actually enjoy mapping you know...

Google Maps maps them as single roads.

Not around here.
http://tinyurl.com/yz8y8dh

The white coloured roads are just roads for a shopping centre. Scroll a bit 
further south, and you'll even see where G-Maps have split the road around a 
long-ish traffic island. A bit further south still, is a motorway junction 
where Google has mapped sliproads (and even marked on a sliproad bypassing 
the roundabout).

The Yahoo for the same location
http://uk.maps.yahoo.com/#mvt=mlat=53.465566lon=-2.354163zoom=18

The principle we have used in the past is where it is not physically 
possible to cross between two carriageways without leaving the road surface 
then mark it as two separate ways. I've not seen a compelling argument 
against continuing this practice. The only argument I've seen from you is 
essentially, it's boring - it takes far too long - which I don't really 
agree with. Dual carriageways all over the world are mapped like this on OSM 
(and it seems Google, Yahoo and I'm sure others do as well).



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Re: [OSM-talk] Divided roads proposal

2009-12-06 Thread Richard Bullock

 Maybe we should be mapping slipways, hopefully there's a better approach
 than marking them all as fully fledged roads though.
 
Sliproads are tagged as highway=xyz_link

e.g. a sliproad to a motorway would be highway=motorway_link
sliproad to a trunk road would be highway=trunk_link etc.

See the wiki map-features page.

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Re: [OSM-talk] Divided roads proposal

( Forgot to FIX the address :( Another crap practice in OSM! )

Richard Bullock wrote:
 The principle we have used in the past is where it is not physically 
 possible to cross between two carriageways without leaving the road surface 
 then mark it as two separate ways. I've not seen a compelling argument 
 against continuing this practice. The only argument I've seen from you is 
 essentially, it's boring - it takes far too long - which I don't really 
 agree with. Dual carriageways all over the world are mapped like this on OSM 
 (and it seems Google, Yahoo and I'm sure others do as well).

And that is what I would agree is the FIRST choice for mapping any divided
structure. You do not bodge the detail so that it renders correctly, the
rendering needs fixing if it is not displayed properly. Trying to add more tags
for situations that ARE already covered by normal mapping practice is wrong.
Adding a tag to cover details that ARE missing is right. So the current proposal
is only acceptable where no physical barrier exists - and therefore the
description is wrong.

( And adding footways properly where pedestrians are kept separate from vehicles
also requires additional ways. Simply adding yet more tags for something which
is not part of the actual roadway is another 'macro' bodge which in reality
requires at least a separate way ... )

-- 
Lester Caine - G8HFL
-
Contact - http://lsces.co.uk/wiki/?page=contact
L.S.Caine Electronic Services - http://lsces.co.uk
EnquirySolve - http://enquirysolve.com/
Model Engineers Digital Workshop - http://medw.co.uk//
Firebird - http://www.firebirdsql.org/index.php


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Re: [OSM-talk] Divided roads proposal

2009-12-06 Thread Anthony

On Sun, Dec 6, 2009 at 4:16 PM, Steve Bennett stevag...@gmail.com wrote:

 Example:

 http://www.openstreetmap.org/?lat=-37.820693lon=144.919989zoom=18layers=B000FTF

 This looks right to you?


I think it could be rendered better, especially if there is width
information provided, but I think it's mapped right, or at least the best it
can be mapped without using areas for everything.

That said, if you only limited your proposal to roads like this where there
is essentially no routing information contained in the divider data, I won't
oppose it.

On Sun, Dec 6, 2009 at 3:56 PM, Steve Bennett stevag...@gmail.com wrote:

 Yahoo — now that I look — does exactly what I'm proposing, rendering a
 single road with a dotted line down the middle to indicate the division.


Yahoo seems to be indicating a center turning lane with that rendering, not
a physical divider.  They happen to also be mapping those small physical
dividers that way, but I suspect that's out of lazy mapping rather than
anything else.


 I think it is essential that slipways are mapped. ESPECIALLY when one is
 trying
 to add the right routing instructions. TomTom has started showing motorway
 and
 major road slipway details properly. You need to know when to get to an
 inside
 lane and take a slip road PRIOR to the actual junction.


 Maybe we should be mapping slipways, hopefully there's a better approach
 than marking them all as fully fledged roads though.


I think now is a good time to bring up the rule against using the word
road on this mailing list.

To put it more clearly, ways do not have a one to one correspondence with
roads.  They never have.
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Re: [OSM-talk] Divided roads proposal

2009-12-06 Thread Anthony

 Google Maps maps them as single roads.

 Not around here.
 http://tinyurl.com/yz8y8dh


Another good example: http://tinyurl.com/ye76u9v

I suspect what you're seeing in cases where Google Maps is using a single
road is simply Google Maps not getting around to fixing its data yet.
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Re: [OSM-talk] Divided roads proposal

2009-12-04 Thread Pieren

On Fri, Dec 4, 2009 at 6:49 AM, Steve Bennett stevag...@gmail.com wrote:
 I don't know how to convince you that I'm not proposing changing the way
 major roads and dual carriageways are mapped. This is about minor divisions
 in minor roads.


I see your point but how can you avoid people using this for major
roads as weel ? A primary road is minor compared to motorways, so it
can be used for primary highways ?. And where is the limit, why should
we fix a limit, what is the criteria of using of not using it, the
width between the two carriage ways, the height, the length ? This
should be clarified in you proposal.

Pieren

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Re: [OSM-talk] Divided roads proposal

2009-12-04 Thread Morten Kjeldgaard


On 04/12/2009, at 06.49, Steve Bennett wrote:

 I don't know how to convince you that I'm not proposing changing the  
 way major roads and dual carriageways are mapped. This is about  
 minor divisions in minor roads.

 Let me ask you: how do you think that a road with a painted traffic  
 island down the middle should be mapped:
 1) As a single road with no special tagging
 2) As a single road with a tag indicating the division
 3) As two separate ways, with ways connecting them every time  
 there's a gap in the painted division.

This discussion is reminiscent of other discussions just like it.

There are two orthogonal approaches to mapping in the OSM. One is the  
drawing approach, which is the most intuitive, since it reminds of  
the way maps have been drawn with paper and pencil for hundreds of  
years. The drawing approach is favoured by newbies and people who  
mostly care about having a beautiful, detailed map to look at. The  
other approach is the tagging appoach, where details about the  
landscape are mapped onto a line passing through it.

The tagging approach to mapping puts emphasis on a graph  
representation of the surrounding world which for example can be used  
for routing, area- and distance determination, and may types of  
statistical and database applications, situations where the drawing  
method doesn't work. Therefore, the tagging method has some digital  
properties that are incridibly useful and powerful, and it is these  
properties that is the innovative secret behind the incredible success  
of OSM.

The regrettable fact is that more and more mappers don't realize the  
incredible power of the tagging approach. Drawing dual carriage roads  
as two separate ways is appealing in many ways since that's how it  
looks. However, it creates problems in more complicated situations,  
for example if intersections with other roads, with cycle- and  
pedenstrian paths are involved, because the connectivity very easily  
gets screwed up. Keeping the connectivity correct forces you to draw  
things that aren't representitive of the real world, and suddenly, the  
drawing isn't pretty. The result is, such as I've seen lately, that  
people start to say why should we care about routing at all?

One example:  an intersection of  two crossing dual carriageways will  
result in four nodes. If the intersection is regulated by a traffc  
light, you will need to specify four traffic lights, but to OSM this  
will appear as four intersections, and passing through the  
intersection, your GPS will think you have to pass two intersections  
instead of one. So, here, while drawing dual carriageways as two ways  
looks right, it is wrong from a topological point of view.

There's nothing you can do with drawing that can't be done with  
tagging, and there's in principle nothing being done with tagging that  
can't be rendered beautifully on the final map. It only depends on the  
richness of the tagging language and the sophistication of the  
renderers.

It is very important that OSM keeps its head straight and doesn't  
succumb to the increasing pressure of making the map a 2D-drawing of  
the world.

Cheers,
Morten
  

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Re: [OSM-talk] Divided roads proposal

2009-12-04 Thread Martin Koppenhoefer

2009/12/4 Morten Kjeldgaard m...@bioxray.dk

 There's nothing you can do with drawing that can't be done with
 tagging, and there's in principle nothing being done with tagging that
 can't be rendered beautifully on the final map. It only depends on the
 richness of the tagging language and the sophistication of the
 renderers.


I just agree partly
1) if you would map intersections of dualcarriage-ways precisely according
to the standards, there would be just 1 intersection node at junctions,
because at the junction there is no physical barrier and therefore the
dualcarriage-way gets 1 way, it doesn't stay 2 parallel ways.
2) there is lots of situations where you can't easily represent complex
geometrical configurations just with tagging. Tagging works well for regular
shaped stuff, but when it comes to more fluid situations (not classical
roads with standard lanes but areas like in pedestrian zones,
living_streets, medieval situations, ... you get the best representation by
drawing an area. Squares are one of the key features for representation of
the individual structure of a city. There shapes tell you about the history
and the influencing factors that interacted while the urban tissue evolved.
3) Drawing dual carriage ways as 2 parallel ways is a very easy way to solve
lots of junctions, where you would otherwise have to add an awful lot of
turning restrictions (or split the way and add divider.tags/relations).
4) It offers also more positional accuracy as well, as dual carriage ways
usually consist of more lanes than the other roads.
See here:
http://maps.google.it/maps?hl=deie=UTF8ll=41.912905,12.481273spn=0.002822,0.004823t=hz=18
situations like this are IMHO not resolveable (with appropriate effort) just
by tagging.
5) Keep it simple. Here are lots of experts discussing about the ideal
scheme, but there are far more users that don't participate in list
discussions (or even read them) and contribute less frequently and IMHO this
group will grow much faster then the expert group. The easier it is for them
to participate, the more they will become.

cheers,
Martin
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Re: [OSM-talk] Divided roads proposal [tagging vs. area mapping]

2009-12-04 Thread Jean-Marc Liotier

Morten Kjeldgaard wrote:
 On 04/12/2009, at 06.49, Steve Bennett wrote:
 
 This discussion is reminiscent of other discussions just like it.

Indeed it now reminds me of the mapping everything as areas thread 
that I recently started.

 There are two orthogonal approaches to mapping in the OSM. One is the  
 drawing approach, which is the most intuitive, since it reminds of  
 the way maps have been drawn with paper and pencil for hundreds of  
 years. The drawing approach is favoured by newbies [..]
 [..]
 There's nothing you can do with drawing that can't be done with  
 tagging, and there's in principle nothing being done with tagging that  
 can't be rendered beautifully on the final map. It only depends on the  
 richness of the tagging language and the sophistication of the  
 renderers.
 
 It is very important that OSM keeps its head straight and doesn't  
 succumb to the increasing pressure of making the map a 2D-drawing of  
 the world.

I'm one of those newbies who got tempted and that was the reason why I 
asked the questions in the above-mentioned thread. Now I am increasingly 
realizing the power of connectivity and how the useful graph results 
from the node  way tagging approach that seems to be the foundation of 
OpenStreetMap as it stands today. Area mapping does have a role, but it 
now seems to be more specialized than my innocent eyes used to believe.

But although I'm learning the ways of OpenStreetMap, I'm learning by 
observing what others do and experimenting on my own. It works and in 
due time I'm sure I'll become a decent mapper, but that process could be 
more efficient. Some people on this list, such as you, seem to have a 
good grasp of the concepts. Would you be so kind as to start a wiki page 
that explains good practices and discernment in choosing what should be 
mapped as a tagged line and what really requires an area ?

I'm sure that the whole project would benefit if arguments could be 
articulated in a demonstration that would convince the wondering newbies 
such as me. There is surely not a single best way, but the need for a 
correct connected graph is definitely a good frame into which our 
methods must fit. Leveraging your experience to get everyone to 
understand that will surely be a significant contribution to data quality.


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Re: [OSM-talk] Divided roads proposal

2009-12-04 Thread Peter Childs

2009/12/4 Martin Koppenhoefer dieterdre...@gmail.com:
 2009/12/4 Morten Kjeldgaard m...@bioxray.dk

 There's nothing you can do with drawing that can't be done with
 tagging, and there's in principle nothing being done with tagging that
 can't be rendered beautifully on the final map. It only depends on the
 richness of the tagging language and the sophistication of the
 renderers.

 I just agree partly

Me Too, however

There are two types of Dual Carrage-way.which I think is the problem here.

Type One.

Large Motor Way Type Roads (but also large Primary roads), with Slip
Roads, and the two separate carriageways are never joined, or maybe by
a roundabout from time to time or other major junction. Here its best
to map each carriage way separately as they are separate roads.

Type Two

Smaller roads where the Dual Carriage way exists but is split at
regular intervals by gaps to turn right (Sorry I'm in the Uk (Left in
most countries)), Often created due to the lay of the land, Bridges,
Tunnels, Crossing Islands, Safety Island, etc. May exist for a few
meters upto a major junction to help traffic flow etc

I think we actually need both, and use the right one for the logic of
the road/junction.

Peter.

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Re: [OSM-talk] Divided roads proposal

2009-12-04 Thread Steve Bennett

Hi all,
  I have rewritten the proposal, using the ideas from here. I've gone for
maximum simplicity, removing all the single-direction u-turn stuff and the
relations on adjoint roads.

Please have a read and comment:
http://wiki.openstreetmap.org/wiki/Proposed_features/Divided_road

Perhaps I should have started a new proposal instead of cannibalising this
one so much. If Vovanium objects, I'll roll it back, and move mine to a new
page. But it's probably best to just have one discussion.

Steve
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Re: [OSM-talk] Divided roads proposal [tagging vs. area mapping]

2009-12-04 Thread Steve Bennett

On Fri, Dec 4, 2009 at 9:22 PM, Jean-Marc Liotier j...@liotier.org wrote:

 I'm sure that the whole project would benefit if arguments could be
 articulated in a demonstration that would convince the wondering newbies
 such as me. There is surely not a single best way, but the need for a
 correct connected graph is definitely a good frame into which our
 methods must fit. Leveraging your experience to get everyone to
 understand that will surely be a significant contribution to data quality.

 I'm new too, and would also appreciate insight. My take in the brief period
of time that I've been doing this is that the connected graph is the first
priority, and everything else is eye candy. A correctly mapped out, but
disconnected, pedestrian mall is much less useful than a simple path that
connects to stuff, for example.

With the advent of high quality aerial photography, it becomes very tempting
to want everything to line up perfectly with the photo. But there are some
cases where it's just not possible:
- bike paths that connect with roads: since the line is down the centre of
the road, and the path, something has to give to make them connect.
- building outlines: I think it's more important to give a shape which
people will recognise, than perhaps the most accurate tracing around the
base of the building.
- big open areas like in industrial sites, that nonetheless have clear
pathways through them. Mapping the pathways is probably more useful than the
vast expanse of asphalt.
- areas with lots of little footpaths that connect. At some point, we should
filter down and map just the most relevant, important ones.

(But as I said, I'm new.)

Steve
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Re: [OSM-talk] Divided roads proposal

2009-12-04 Thread Richard Mann

+1 (on tagging vs drawing models)

I think it's a good rule of thumb that if it can't be rendered easily, then
you need to look again at your tagging model - your data isn't structured in
a way that is usable

Never tag for a renderer. Always tag for the renderers.

Richard

On Fri, Dec 4, 2009 at 9:35 AM, Morten Kjeldgaard m...@bioxray.dk wrote:

 This discussion is reminiscent of other discussions just like it.

 There are two orthogonal approaches to mapping in the OSM. One is the
 drawing approach, which is the most intuitive, since it reminds of
 the way maps have been drawn with paper and pencil for hundreds of
 years. The drawing approach is favoured by newbies and people who
 mostly care about having a beautiful, detailed map to look at. The
 other approach is the tagging appoach, where details about the
 landscape are mapped onto a line passing through it.

 The tagging approach to mapping puts emphasis on a graph
 representation of the surrounding world which for example can be used
 for routing, area- and distance determination, and may types of
 statistical and database applications, situations where the drawing
 method doesn't work. Therefore, the tagging method has some digital
 properties that are incridibly useful and powerful, and it is these
 properties that is the innovative secret behind the incredible success
 of OSM.

 The regrettable fact is that more and more mappers don't realize the
 incredible power of the tagging approach. Drawing dual carriage roads
 as two separate ways is appealing in many ways since that's how it
 looks. However, it creates problems in more complicated situations,
 for example if intersections with other roads, with cycle- and
 pedenstrian paths are involved, because the connectivity very easily
 gets screwed up. Keeping the connectivity correct forces you to draw
 things that aren't representitive of the real world, and suddenly, the
 drawing isn't pretty. The result is, such as I've seen lately, that
 people start to say why should we care about routing at all?

 One example:  an intersection of  two crossing dual carriageways will
 result in four nodes. If the intersection is regulated by a traffc
 light, you will need to specify four traffic lights, but to OSM this
 will appear as four intersections, and passing through the
 intersection, your GPS will think you have to pass two intersections
 instead of one. So, here, while drawing dual carriageways as two ways
 looks right, it is wrong from a topological point of view.

 There's nothing you can do with drawing that can't be done with
 tagging, and there's in principle nothing being done with tagging that
 can't be rendered beautifully on the final map. It only depends on the
 richness of the tagging language and the sophistication of the
 renderers.

 It is very important that OSM keeps its head straight and doesn't
 succumb to the increasing pressure of making the map a 2D-drawing of
 the world.

 Cheers,
 Morten


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Re: [OSM-talk] Divided roads proposal

2009-12-04 Thread Steve Bennett

On Fri, Dec 4, 2009 at 5:04 PM, John Smith deltafoxtrot...@gmail.comwrote:

 This opens up a can of worms about micro mapping.

 You either need to split the way to accomodate your suggestion or some
 other micromapping technique to accomlish this, in any case you are
 adding almost nothing that a legal turning restriction won't presently
 accomplish. I don't think painted lines are the same thing as properly
 divided ways and don't really need anything that special to
 distinguish them.


Ok, I've uploaded 10 examples of median strips here:

http://wiki.openstreetmap.org/wiki/Talk:Proposed_features/Divided_road#Images_for_discussion

Hopefully we can use them to discuss whether this proposal is helpful, and
what alternatives there might be otherwise. In most of these images, I think
either we would still map it with two ways (even if the divided=* tag
exists), or we would currently just leave it as a single way, missing out on
detail.

Would love to hear your thoughts there.

Steve
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Re: [OSM-talk] Divided roads proposal

2009-12-04 Thread Anthony

On Fri, Dec 4, 2009 at 8:27 AM, Steve Bennett stevag...@gmail.com wrote:
Ok, I've uploaded 10 examples of median strips here:

http://wiki.openstreetmap.org/wiki/Talk:Proposed_features/Divided_road#Images_for_discussion

Hopefully we can use them to discuss whether this proposal is helpful, and
what alternatives there might be otherwise.

1, 2. Dual carriageway
3. Assuming these roads eventually divide, I'd personally use a dual
carriageway, however, this is disputed. Currently, this could be best
handled with three highway areas, with the highway in the center
marked as access=no (in jurisdictions where crossing that gore area is
prohibited, I can't tell the jurisdiction from the photo). In
jurisdictions where those painted gore areas mean use a lot of extra
care when crossing, this could be mapped as a single way.
4. Looks easiest to map accurately as a highway area with several
barrier=* areas. Are we allowed to make highway multipolygons? Or
just ignore it, as it's so insignificant, and use a single way. I
don't see any other markings in this photo, if there are signs, I've
ignored them because I can't see them. I see no lane markings, so it
fits with area=yes, in the context of roads, indicates that the area
has no street lines within it.
5, 6, 7, 8, 9, 10. Dual carriageway

Regarding 3, hopefully we can eventually get a solution for directed
highway areas, whether that means using both an area and a way, or (my
current preference) using a relation with role=left, role=right, and
role=outer, then oneway=yes to represent that vehicles must travel
forward with respect to the left and right ways. However, they would
really be unnecessary here, because both the incoming and outgoing
ways would already be oneway=yes, so there's basically no way a router
would direct you backward on them (I guess it might if you asked for
directions from one spot to another within the same area!).

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Re: [OSM-talk] Divided roads proposal

2009-12-04 Thread Morten Kjeldgaard

Peter Childs wrote:

 There are two types of Dual Carrage-way.which I think is the problem here.
 
 Type One.
 
 Large Motor Way Type Roads (but also large Primary roads), with Slip
 Roads, and the two separate carriageways are never joined, or maybe by
 a roundabout from time to time or other major junction. Here its best
 to map each carriage way separately as they are separate roads.
 
 Type Two
 
 Smaller roads where the Dual Carriage way exists but is split at
 regular intervals by gaps to turn right (Sorry I'm in the Uk (Left in
 most countries)), Often created due to the lay of the land, Bridges,
 Tunnels, Crossing Islands, Safety Island, etc. May exist for a few
 meters upto a major junction to help traffic flow etc
 
 I think we actually need both, and use the right one for the logic of
 the road/junction.

+1

There is a very important point here: there's not a single unifying idea
that we can come up with that describes every situation. Ultimately, beauty
is in simplicity.

The example with the motorway is interesting, because on one hand, we think
of it as the motorway from A to B, but when analysing its topology, it is
perhaps more correct to think of it as one road from B to A and another road
from A to B... that happens to be next to it. The distinctive feature is
that the two roads are actually not connected directly, i.e. you need to
travel along another road in order to reverse directions.

The second example you mention is on the other end of the spectrum. A split
road is from a topological standpoint a single road, since you could make a
U-turn on it (some places even without breaking the law) if you want to
reverse directions.

I think these are useful rules-of-thumb to keep in mind. In practice, there
are other issues, such as the number of T- and X- intersections etc. that
may influence how a particular segment of road is best mapped as simply as
possible.


Jean-Marc Liotier wrote:

 But although I'm learning the ways of OpenStreetMap, I'm learning by
 observing what others do and experimenting on my own. It works and in
 due time I'm sure I'll become a decent mapper, but that process could be
 more efficient. Some people on this list, such as you, seem to have a
 good grasp of the concepts. Would you be so kind as to start a wiki page
 that explains good practices and discernment in choosing what should be
 mapped as a tagged line and what really requires an area ?

In connection with a discussion we are currently having on the talk-dk list
about how to map cycleways I recently made a page on the wiki [0]. The
purpose of the page is to explore the different problems/benefits you
encounter when mapping cycleways as separate ways, vs. mapping them as
tagged onto the road itself.

These problems are similar to the current discussion on dual carriageways.

Making this wiki page was an exercise to enlighten myself and (hopefully)
others, and I learned a lot from making these diagrams. The page is in
danish, but you can probably grasp the meaning by looking at the diagrams.
If there's interest, I can translate the text to english.

(You can't use the diagrams as best practice examples, because some of
them are actually incorrect or bad practice :-) )

Wrt. the line vs. area problem, it's interesting, but a little bit OT in
this thread, so let's discuss it separately (so not to lose focus.)

Cheers,
Morten

[0] http://wiki.openstreetmap.org/wiki/Da:Cykelstier

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Re: [OSM-talk] Divided roads proposal

2009-12-04 Thread Anthony

On Fri, Dec 4, 2009 at 10:03 AM, Morten Kjeldgaard m...@bioxray.dk wrote:
 In connection with a discussion we are currently having on the talk-dk
list
 about how to map cycleways I recently made a page on the wiki [0]. The
 purpose of the page is to explore the different problems/benefits you
 encounter when mapping cycleways as separate ways, vs. mapping them as
 tagged onto the road itself.

 These problems are similar to the current discussion on dual carriageways.

Yeah, they're pretty much exactly the same.

At least, here in Florida.  Bicycles are allowed to use a dedicated bike
lane, or, in certain situations such as when preparing to make a turn, can
use the regular roadway.  So using two separate ways doesn't really convey
the reality of the situation.  We really have a (for example) three lane
highway, with two lanes for cars and bicycles, and one lane for bicycles
only.  There is nothing but a thick white line separating the bike lane from
the other lanes, so using more than one way is inappropriate.

Basically, we need to find a way to map lanes, and we need a way to connect
those lanes along ways and not just at individual nodes.  The latest
strategy I've been thinking about is to use areas.  Areas can be connected
together along ways, and not just at individual nodes, so it's almost
perfect.  Perfect until you try to add a oneway tag.

I'll have to draw something up...

1--2
||
3--4
||
||
5--6
||
7--8
||
||
9--0

way id=34
 nd ref=3
 nd ref=4
 tag k=divider v=line
 tag k=line v=lane_change_allowed (or v=lane_change_prohibited, or
v=change_with_extra_care, etc.)
/way

relation id=1234
 member type=way ref=12 role=left
 member type=way ref=13 role=outer
 member type=way ref=34 role=right
 member type=way ref=24 role=outer
 tag k=type v=directed_area
 tag k=highway v=cycleway
 tag k=oneway v=yes
/relation
relation id=3456
 member type=way ref=34 role=left
 member type=way ref=35 role=outer
 member type=way ref=56 role=right
 member type=way ref=46 role=outer
 tag k=type v=directed_area
 tag k=highway v=secondary
 tag k=oneway v=yes
/relation
relation id=5678
 member type=way ref=56 role=outer
 member type=way ref=57 role=outer
 member type=way ref=78 role=outer
 member type=way ref=68 role=outer
 tag k=type v=multipolygon
 tag k=barrier v=traffic_island
 tag k=surface v=grass
 tag k=foot v=yes
/relation
relation id=7890
 member type=way ref=90 role=left
 member type=way ref=79 role=outer
 member type=way ref=78 role=right
 member type=way ref=80 role=outer
 tag k=type v=directed_area
 tag k=highway v=secondary
 tag k=oneway v=yes
/relation

Editor support would obviously be helpful, but isn't an absolute
requirement.
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Re: [OSM-talk] Divided roads proposal

2009-12-04 Thread Lester Caine

Anthony wrote:
On Fri, Dec 4, 2009 at 8:27 AM, Steve Bennett stevag...@gmail.com wrote:
Ok, I've uploaded 10 examples of median strips here:

http://wiki.openstreetmap.org/wiki/Talk:Proposed_features/Divided_road#Images_for_discussion

Hopefully we can use them to discuss whether this proposal is helpful, and
what alternatives there might be otherwise.

Seconded - I think in most of these cases, the connection to the other roads
dictates that they need to be split and correctly join other ways. 5 for
example
would seem to be best described as a 'roundabout' as it certainly looks like it
is for turning around.

3 as actually just a wide road marking. Such cross hatch areas do need to be
covered but this a single road with 'advisory' road marking rather than a
divider?

--
Lester Caine - G8HFL
-
Contact - http://lsces.co.uk/wiki/?page=contact
L.S.Caine Electronic Services - http://lsces.co.uk
EnquirySolve - http://enquirysolve.com/
Model Engineers Digital Workshop - http://medw.co.uk//
Firebird - http://www.firebirdsql.org/index.php

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Re: [OSM-talk] Divided roads proposal

2009-12-04 Thread Anthony

On Fri, Dec 4, 2009 at 11:49 AM, Lester Caine les...@lsces.co.uk wrote:

 3 as actually just a wide road marking. Such cross hatch areas do need to
 be
 covered but this a single road with 'advisory' road marking rather than a
 divider?


I don't know.  I actually got a traffic ticket once for going through a
cross hatch area, and I researched it in depth to try to see whether or not
it was legit.  In the end, I couldn't find any definitive statement one way
or the other, and I wound up paying the ticket rather than taking a day off
work to try to fight it.  I think I was right, that it basically means use
lots and lots of extra caution when changing lanes (*), but I wasn't 100%
sure (plus I figured there would then be a dispute as to whether or not I
used lots and lots of extra caution).

(*) A solid white line means lane change is discouraged, wide lines are
used for extra emphasis, and chevrons are used for special emphasis.
But the lines are referred to as channelizing lines, and the area is
referred to as a gore area, which suggests to me that it might be
considered legally equivalent to non-roadway.



In any case, I think it would be useful to map these painted areas as areas,
regardless of whether or not it is technically legal to drive over them
(which probably varies from jurisdiction to jurisdiction anyway).  If
they're illegal to drive over, we can then add access=no, which satisfies
people who want routing information for emergency vehicles or for people who
just don't care about breaking the law.  Unfortunately, connecting an area,
to a way which is adjacent to it, doesn't work.
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Re: [OSM-talk] Divided roads proposal [tagging vs. area mapping]

2009-12-04 Thread Martin Koppenhoefer

2009/12/4 Steve Bennett stevag...@gmail.com

I'm new too, and would also appreciate insight. My take in the brief period
 of time that I've been doing this is that the connected graph is the first
 priority, and everything else is eye candy. A correctly mapped out, but
 disconnected, pedestrian mall is much less useful than a simple path that
 connects to stuff, for example.


depends what you want to do with the map. When focusing on routing outside
the mall: yes, when interested in routing for far distances: doesn't matter,
when interested in routing inside the mall you'll prefer to have details and
won't care whether it's connected to the outside...



 - bike paths that connect with roads: since the line is down the centre of
 the road, and the path, something has to give to make them connect.


yep, that's a small problem


  - building outlines: I think it's more important to give a shape which
 people will recognise, than perhaps the most accurate tracing around the
 base of the building.


IMHO the better the outline is matching reality the better you will
recognise the building (but we could have several outlines for different
heights, I agree, e.g. a tower-building/skyscraper often has a bigger base
and gets taller due to zoning-laws)


 - big open areas like in industrial sites, that nonetheless have clear
 pathways through them. Mapping the pathways is probably more useful than the
 vast expanse of asphalt.


I do generally both.


 - areas with lots of little footpaths that connect. At some point, we
 should filter down and map just the most relevant, important ones.


everyone is free to map whatever he/she likes. As long as you don't delete
footpaths mapped by other people because you don't consider them relevant,
that's not a problem.

cheers,
Martin
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Re: [OSM-talk] Divided roads proposal

2009/12/3 Steve Bennett stevag...@gmail.com:
 I find the current practice of duplicating minor roads when there is a
 median strip pretty unsatisfactory. Even disregarding the effort, the
 end result never renders well: usually the street name is written
 twice, the one-way arrows get messy etc.

That's a problem with the rendering, not with the mapping.

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Re: [OSM-talk] Divided roads proposal

2009-12-03 Thread Richard Mann

On Thu, Dec 3, 2009 at 9:39 AM, John Smith deltafoxtrot...@gmail.comwrote:

 2009/12/3 Steve Bennett stevag...@gmail.com:
  I find the current practice of duplicating minor roads when there is a
  median strip pretty unsatisfactory. Even disregarding the effort, the
  end result never renders well: usually the street name is written
  twice, the one-way arrows get messy etc.

 That's a problem with the rendering, not with the mapping.

Unless you want to write routines for pre-processing two almost-parallel
ways back into a single way so it can be rendered neatly, I suggest it's a
mapping problem. Don't make work for other people if you don't have to.

Everything about a dual carriageway can (now) be expressed using turn
restriction relations, and it would probably be better if it were done that
way.

Richard
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Re: [OSM-talk] Divided roads proposal

2009-12-03 Thread Pieren

On Thu, Dec 3, 2009 at 11:17 AM, Richard Mann
 That's a problem with the rendering, not with the mapping.

 Unless you want to write routines for pre-processing two almost-parallel
 ways back into a single way so it can be rendered neatly, I suggest it's a
 mapping problem. Don't make work for other people if you don't have to.

It's both, a rendering issue when the names are duplicated and a
mapping issue about representing the turn restrictions. Note that It's
a very old definition in OSM to say that we duplicate the ways when
there is a physical division between the two ways (it's physically
impossible to cross the road with a car, e.g. a sidewalk, a wall, a
fence, grassland). A simple painted white line is not enough.
I personnaly prefer to draw two ways and the connections where they
exist than creating dozen turn restrictions.

It's funny to see the whole discussions about drawing every single
lanes or everything as areas and this proposal.

Pieren

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Re: [OSM-talk] Divided roads proposal

On Thu, Dec 3, 2009 at 9:17 PM, Richard Mann
richard.mann.westoxf...@googlemail.com wrote:
 That's a problem with the rendering, not with the mapping.

 Unless you want to write routines for pre-processing two almost-parallel
 ways back into a single way so it can be rendered neatly, I suggest it's a
 mapping problem.

Yep, a very hard rendering problem, or an easy mapping problem.

 Everything about a dual carriageway can (now) be expressed using turn
 restriction relations, and it would probably be better if it were done that
 way.

I don't want to be as ambitious as genuine dual carriage motorways,
but it would be great for minor roads.

Here's an example I came across (I didn't map it):

http://www.openstreetmap.org/?lat=-37.824316lon=144.940393zoom=18layers=B000FTF

See Hartley St there? It's a tiny pathetic service road that happens
to have some concrete blocks down the middle of some sections. I can
just picture how nicely this would render with the right tagging and
styles...

Another example, nearby:
http://www.openstreetmap.org/?lat=-37.81993lon=144.960348zoom=18layers=B000FTF

Queensbridge St, where it splits from the bridge itself. The two lanes
are actually separated by a decent chunk of concrete. The northbound
lane then splits again just before hitting Flinders St. I don't blame
the mapper for not representing all this detail, because ultimately it
doesn't really make a difference to anyone using the map, and it will
render as a mess.

Another really cool thing you could do with this proposal (not
currently suggested) is a width parameter. Then you could really
precisely control the separation of the lanes, which are now a bit hit
and miss - it's very hard to specify how much gap there is, because
you have to guess how wide the renderer will think the road is, then
compensate for that.

Steve

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Re: [OSM-talk] Divided roads proposal

Sorry, one last example, also nearby:

http://www.openstreetmap.org/?lat=-37.826282lon=144.947554zoom=18layers=B000FTF

This mess might be much more understandable if pairs of lanes that
were physically together were rendered as pairs (with a line between
them), and those that were on separate physical carriageways had the
separation as at present.

Note that It's a very old definition in OSM to say that we duplicate the ways 
when there is a physical division between the two ways

Is that an argument against changing it?

Steve

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Re: [OSM-talk] Divided roads proposal

2009-12-03 Thread Morten Kjeldgaard


On 03/12/2009, at 10.39, John Smith wrote:

 2009/12/3 Steve Bennett stevag...@gmail.com:
 I find the current practice of duplicating minor roads when there  
 is a
 median strip pretty unsatisfactory. Even disregarding the effort, the
 end result never renders well: usually the street name is written
 twice, the one-way arrows get messy etc.

 That's a problem with the rendering, not with the mapping.

And that's a problem with a knee-jerk reaction to a quite reasonable  
discussion.

-- Morten

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Re: [OSM-talk] Divided roads proposal

Ok, I've mocked up what it might look like.

Complicated to show you though:

1) http://www.geowiki.com/halcyon/

2) Lat: -37.821995  Lon: 144.919573

3) Add these lines to the of end of the big edit box:


way[highway=service][!divider]
{ color: white; width: 3; casing-width: 5; }

way[divider=median][highway=service]
{ z-index:5; color:white; width:7; casing-width:9; linecap:round;}
{ z-index:6; color:brown; width:2;}


Pretty, and a huge improvement on real separated lanes.

Steve

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Re: [OSM-talk] Divided roads proposal

2009/12/3 Steve Bennett stevag...@gmail.com

 Can I draw some attention to this:

 http://wiki.openstreetmap.org/wiki/Proposed_features/Divided_road

 I was going to propose exactly the same thing, pretty much. Maybe I'd
 quibble with some of the naming.


I am also working on a proposal (let's say it's in an very early phase) to
cope with dividers but also the opposite (no divider but linear possibility
to change way/lane), so I'd consider this in a more generalized way.

My first draft is here, you're welcome to comment:
http://wiki.openstreetmap.org/wiki/User:Dieterdreist/drafts

it allows to define things like: there is a kerb between the footway and the
street, but on given nodes there is a lowered kerb to crossover.

Or: these two ways are separated by a grass-divider (what does actually
permit pedestrians to cross at any place)

Or: this link is connected from the motorway between Node A and Node B
(probably would need to be a way, so splitting required)

Or: this is a lane that will turn right on next crossing (highway=lane,
turn=right), and changing to this lane is possible from A to B, from B to C
there is a uninterupted line, while from C to D the way must be mapped
separately (as it is divided physically). This would require somehow double
mapping and tagging (as there has to be a artificial way that connects the
original (main) way to node C, (which is the last changeover possibility for
the lane) as a normal way (so that applications can do routing considering
the lanes but will work also not knowing about them).

This should also work to map pedestrian areas beside roads: between this
road and this building there is a pedestrian area.

cheers,
Martin
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Re: [OSM-talk] Divided roads proposal

On Thu, Dec 3, 2009 at 10:15 PM, Martin Koppenhoefer
dieterdre...@gmail.com wrote:
 it allows to define things like: there is a kerb between the footway and the
 street, but on given nodes there is a lowered kerb to crossover.

Yes, it's certainly quite expressive, at the cost of complexity - and
having to use relations. One of the advantages of simply setting a
divider= tag is its simplicity and succinctness. One tag, and you've
got something that will render nicely, and be useful for routing.

I see four essential tag values:

divider=none (can freely cross)
divider=marked or something (do not route a car across this, but a
pedestrian could cross it)
divider=median_strip (again, do not route a car across this, but you
could drive across it in an emergency)
divider=barrier (a physical barrier that would probably stop a pedestrian)

Not certain about the key or tag names. Maybe:
divided=no
divided=line
divided=median
divided=barrier

Does that work? median=?

I guess we also have to be careful about the word barrier. Setting a
highway to be barrier=yes would normally mean the highway itself is
somehow impassable to people not on it...but wouldn't say anything
about u-turns.

Steve

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Re: [OSM-talk] Divided roads proposal

Oops, I also meant to point out a screenshot of my mockup:

http://wiki.openstreetmap.org/wiki/Image:Stevage_Divided_road.png

(And an earlier version:
http://wiki.openstreetmap.org/images/archive/9/9e/20091203113817!Stevage_Divided_road.png
)

Sorry for the spam.

Steve

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Re: [OSM-talk] Divided roads proposal

2009-12-03 Thread Pieren

On Thu, Dec 3, 2009 at 12:47 PM, Steve Bennett stevag...@gmail.com wrote:
 http://wiki.openstreetmap.org/wiki/Image:Stevage_Divided_road.png


If dividers are so small and do not create any turn restrictions, I
just ignore them.
But you are lucky to have a source which allow you to go so deep in
details. Anyway, your rendered example looks nice but you create other
difficulties like drawing the street name.

Pieren

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Re: [OSM-talk] Divided roads proposal

2009/12/3 Steve Bennett stevag...@gmail.com

 On Thu, Dec 3, 2009 at 10:15 PM, Martin Koppenhoefer
 dieterdre...@gmail.com wrote:
  it allows to define things like: there is a kerb between the footway and
 the
  street, but on given nodes there is a lowered kerb to crossover.

 Yes, it's certainly quite expressive, at the cost of complexity - and
 having to use relations.



+1


 One of the advantages of simply setting a
 divider= tag is its simplicity and succinctness. One tag, and you've
 got something that will render nicely, and be useful for routing.


but haven't we already barrier for this?


 I see four essential tag values:

 divider=none (can freely cross)
 divider=marked or something (do not route a car across this, but a
 pedestrian could cross it)
 divider=median_strip (again, do not route a car across this, but you
 could drive across it in an emergency)
 divider=barrier (a physical barrier that would probably stop a pedestrian)


yes, I see these as possible dividers/barriers for my proposed
area-relation. The area-relation allows optionally to add a
divider/barrier-role, which can be either area (e.g. if it is a very thick
irregular wall), way or node (nodes can be barriers, but also the opposite:
entrances (interruptions, openings), gates, lift_gates, lowered_kerbs, ...)

And it can solve the lane-problem (map lanes explicitly and do not confound
them with other highway-ways), connect bicycle-tracks to the adjacent road
and define the height of the kerb (without having to map the kerb, but
beeing able to map the kerb-lowerings), 

cheers,
Martin
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Re: [OSM-talk] Divided roads proposal

moved to proposal from user-space to
http://wiki.openstreetmap.org/wiki/Relations/Proposed/Area

cheers,
Martin
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Re: [OSM-talk] Divided roads proposal

2009-12-03 Thread Nick Whitelegg

It's both, a rendering issue when the names are duplicated and a
mapping issue about representing the turn restrictions. Note that It's
a very old definition in OSM to say that we duplicate the ways when
there is a physical division between the two ways (it's physically
impossible to cross the road with a car, e.g. a sidewalk, a wall, a
fence, grassland). A simple painted white line is not enough.

Agreed, while it's sensible for two ways in a dual carriageway, it seems 
OTT to have two ways for a road simply because it's got white lines down 
the middle. It seems to me to be introducing unnecessary complication, not 
to mention increasing required storage size and bandwidth for transmitting 
the data or the need for pre-processing tools to remove it if you're not 
interested in it for your purposes.

Nick

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Re: [OSM-talk] Divided roads proposal

On Thu, Dec 3, 2009 at 4:06 AM, Steve Bennett stevag...@gmail.com wrote:
 I find the current practice of duplicating minor roads when there is a
 median strip pretty unsatisfactory.

I was thinking about this recently when we had the map everything as
areas thread, and I have to agree with you to some extent (though not
completely).  Duplicating and separating makes more sense when the
roads are completely separate - separate entrance/exit ramps, etc.
For a road with a median strip, we're better off mapping the median
strip on top of the road.

I'm not sure how this would work without using areas, though.  And
even then, it'll be complicated.  I think the proposal at
http://wiki.openstreetmap.org/wiki/Proposed_features/Divided_road is
far too kludgy and temporary to justify going through the database and
merging ways which were separated to represent roads with traffic
islands.  And doing so will likely lose data - specifically, the size
of the divider (which varies often enough to make divider:width=* an
insufficient solution).

On Thu, Dec 3, 2009 at 5:17 AM, Richard Mann
richard.mann.westoxf...@googlemail.com wrote:
 On Thu, Dec 3, 2009 at 9:39 AM, John Smith deltafoxtrot...@gmail.com
 wrote:

 2009/12/3 Steve Bennett stevag...@gmail.com:
  I find the current practice of duplicating minor roads when there is a
  median strip pretty unsatisfactory. Even disregarding the effort, the
  end result never renders well: usually the street name is written
  twice, the one-way arrows get messy etc.

 That's a problem with the rendering, not with the mapping.

 Unless you want to write routines for pre-processing two almost-parallel
 ways back into a single way so it can be rendered neatly, I suggest it's a
 mapping problem. Don't make work for other people if you don't have to.

The thing is, you kind of have to.  There has never been a one-to-one
correspondence between roads and ways.  It's not just dual
carriageways that sometimes get rendered poorly, it happens when ways
are split as well.

Mappers could assist the renderers by creating relations, so every
single way which is part of Dale Mabry Highway (as in
http://en.wikipedia.org/wiki/Dale_Mabry_Highway) gets put into a
single relation.  I think that's more the way to go.  Solves lots of
problems in addition to that one.

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Re: [OSM-talk] Divided roads proposal

On Fri, Dec 4, 2009 at 12:40 AM, Nick Whitelegg nick.whitel...@solent.ac.uk
wrote:
 Agreed, while it's sensible for two ways in a dual carriageway, it seems
 OTT to have two ways for a road simply because it's got white lines down
 the middle. It seems to me to be introducing unnecessary complication, not
 to mention increasing required storage size and bandwidth for transmitting
 the data or the need for pre-processing tools to remove it if you're not
 interested in it for your purposes.

Ok, so no one has raised objections so far. What's the next stage to getting
this adopted? Open the RFC? Work on the proposal itself more first?

For example I'm not sure I see the need for the relation - but maybe I'm not
understanding it. As I see it, when there's a junction:

  |
==+==
  |

Either the N-S street can go through, or it can't. That's a simple flag best
set on the node (junction=*). By default I'd say it doesn't go through, it's
two separate side streets each feeding into a street with a median strip.

Incidentally, I've uploaded a pic showing three types of divider:
http://wiki.openstreetmap.org/wiki/Proposed_features/Divided_road

I was just mapping out a new suburb, and really realising how ridiculous it
is to make two lanes every time there's a divided street. I really hope we
can get this implemented. It would also be useful at roundabouts, where the
streets are briefly divided when they meet the roundabout.

Steve
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Re: [OSM-talk] Divided roads proposal

On Fri, Dec 4, 2009 at 2:40 AM, Anthony o...@inbox.org wrote:
 I'm not sure how this would work without using areas, though.  And
 even then, it'll be complicated.  I think the proposal at
 http://wiki.openstreetmap.org/wiki/Proposed_features/Divided_road is
 far too kludgy and temporary

What do you find kludgy about it? I thought it was quite elegant? It
makes the division a property of the road, and lends itself to
assisting with routing.

to justify going through the database and
 merging ways which were separated to represent roads with traffic
 islands.

I don't think anyone was proposing doing that. I mean, one *could* but
I don't see what the compulsion would be.

  And doing so will likely lose data - specifically, the size
 of the divider (which varies often enough to make divider:width=* an
 insufficient solution).

Well, a couple of comments there:
1) Do you think the divider widths as currently recorded are
particularly accurate?
2) Do you think it's important?
3) Do you think in a situation where we had accurate information about
a non-uniform-width divided road, we would even consider throwing out
that information and replacing it with this? Of course not.

The point is, certainly in the areas I'm working in, there are lots of
back streets with median strips that are sketched out fairly quickly,
and there's nothing particularly interesting or important about the
width of that strip, and using two separate ways to indicate the lanes
on either side - *that's* the kludge. It's implying a higher level of
accuracy and detail than we have.

 The thing is, you kind of have to.  There has never been a one-to-one
 correspondence between roads and ways.  It's not just dual
 carriageways that sometimes get rendered poorly, it happens when ways
 are split as well.

Yep, this proposal doesn't solve every problem.

 Mappers could assist the renderers by creating relations, so every
 single way which is part of Dale Mabry Highway (as in
 http://en.wikipedia.org/wiki/Dale_Mabry_Highway) gets put into a
 single relation.  I think that's more the way to go.  Solves lots of
 problems in addition to that one.

Yeah...but before that happens, the interface for editing relations
has to be really natural. And it would still be much more work than
simply marking a stretch of road. Better rendering is just one
benefit.

Steve

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Re: [OSM-talk] Divided roads proposal

On Thu, Dec 3, 2009 at 10:58 AM, Steve Bennett stevag...@gmail.com wrote:
 On Fri, Dec 4, 2009 at 2:40 AM, Anthony o...@inbox.org wrote:
 I'm not sure how this would work without using areas, though.  And
 even then, it'll be complicated.  I think the proposal at
 http://wiki.openstreetmap.org/wiki/Proposed_features/Divided_road is
 far too kludgy and temporary

 What do you find kludgy about it? I thought it was quite elegant? It
 makes the division a property of the road, and lends itself to
 assisting with routing.

It doesn't seem to be general enough, but instead as an incomplete
lump of special cases.

to justify going through the database and
 merging ways which were separated to represent roads with traffic
 islands.

 I don't think anyone was proposing doing that. I mean, one *could* but
 I don't see what the compulsion would be.

So routers are going to have to handle two completely different ways
of doing the same thing?


  And doing so will likely lose data - specifically, the size
 of the divider (which varies often enough to make divider:width=* an
 insufficient solution).

 Well, a couple of comments there:
 1) Do you think the divider widths as currently recorded are
 particularly accurate?

The ones I've done are.

 2) Do you think it's important?

Not of huge importance, but I think it's something important enough
that it should eventually be recorded.

 3) Do you think in a situation where we had accurate information about
 a non-uniform-width divided road, we would even consider throwing out
 that information and replacing it with this? Of course not.

See above regarding mapping the same thing two different ways.

 The point is, certainly in the areas I'm working in, there are lots of
 back streets with median strips that are sketched out fairly quickly,
 and there's nothing particularly interesting or important about the
 width of that strip, and using two separate ways to indicate the lanes
 on either side - *that's* the kludge. It's implying a higher level of
 accuracy and detail than we have.

I guess I'm spoiled with access to Yahoo aerials.  Still, if there's
nothing interesting about the median, why bother mapping it in the
first place?  You can still add the turn restrictions, which is the
important part.

 Mappers could assist the renderers by creating relations, so every
 single way which is part of Dale Mabry Highway (as in
 http://en.wikipedia.org/wiki/Dale_Mabry_Highway) gets put into a
 single relation.  I think that's more the way to go.  Solves lots of
 problems in addition to that one.

 Yeah...but before that happens, the interface for editing relations
 has to be really natural.

I don't see why it does.  In fact, I think you're putting the cart
before the horse.  Define the relation in the wiki, and the editors
will follow.

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Re: [OSM-talk] Divided roads proposal

On Fri, Dec 4, 2009 at 3:14 AM, Anthony o...@inbox.org wrote:
 It doesn't seem to be general enough, but instead as an incomplete
 lump of special cases.

It covers the small, but salient, case of divided roads. Nothing more.
We're just talking about one key here.

 So routers are going to have to handle two completely different ways
 of doing the same thing?

I'm not sure what you're getting at. Topologically speaking, the way a
divided road is handled now is the same as two parallel streets with
occasional cross streets. Routers handle that case in the way they
handle any other street routing. With the new divider tag, a divided
road is handled just like a single street - again, a case it already
has to handle. The only difference is that it has to check before
turning right (or left in othe countries), when u-turning, and when
crossing a junction. All these checks already have to be performed,
and there's just a very small amount of additional logic.

(I haven't seen router code, I'm just speculating here, but the tests
involved seem trivial.)

 1) Do you think the divider widths as currently recorded are
 particularly accurate?

 The ones I've done are.

 2) Do you think it's important?

 Not of huge importance, but I think it's something important enough
 that it should eventually be recorded.

I should also have asked whether the widths of the roads are
accurately measured. Presumably we need to know the width of each road
and the distance between them, at each point. But if you want to model
the roads that accurately, probably best to keep them as separate
lanes, or use an area tag or something.

 I guess I'm spoiled with access to Yahoo aerials.  Still, if there's
 nothing interesting about the median, why bother mapping it in the
 first place?  You can still add the turn restrictions, which is the
 important part.

Why? Primarily as a landmark, I would think. The fact that there is a
median strip is more important, relatively, than that there is a
median strip which is 83cm wide, surfaced in terracotta pavers
overgrown with moss...

Anyway, to back up slightly here, the benefits of this proposal are:
- much simpler and faster entry of minor divided roads
- better rendering at little cost
- cleaner data structure that better reflects what we're trying to map

The downsides are:
- less specificity of the width of the division

Are there other downsides I'm missing? Could you explain the lack of
generality argument - what cases can't it handle, and why is this
important?

Steve

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Re: [OSM-talk] Divided roads proposal

On Thu, Dec 3, 2009 at 12:05 PM, Steve Bennett stevag...@gmail.com wrote:
 I should also have asked whether the widths of the roads are
 accurately measured. Presumably we need to know the width of each road
 and the distance between them, at each point. But if you want to model
 the roads that accurately, probably best to keep them as separate
 lanes, or use an area tag or something.

And I think that's eventually where we're going.  The distance between
the centerlines is only part of the equation, but I wouldn't want to
throw that information away.  This is all moot, however, because I now
understand that you have no intention of throwing that information
away.  The old way of doing things would still be allowed, and in fact
would not be deprecated, right?

 Are there other downsides I'm missing?

I think the biggest downside is that it creates two accepted ways to
map the same thing.  Even that, I suppose, is not a problem, if we
make it clear that the old way, which contains more information, is
preferable.

Your initial email suggested to me that this method of mapping was
superior to the old one.  You made a statement, which I agree with,
that the current practice of duplicating minor roads when there is a
median strip [is] pretty unsatisfactory.  So I thought you were
attempting to replace that current practice.

You've clarified that you're not, and it looks like a router/renderer
would be safe ignoring these new tags, so I guess I don't object.

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Re: [OSM-talk] Divided roads proposal

On Thu, Dec 3, 2009 at 12:05 PM, Steve Bennett stevag...@gmail.com wrote:
 Are there other downsides I'm missing?

Oh yeah, I forgot to mention a big problem.  Using forward/backward
breaks when a way is reversed.  So divider=u_turn_forward and
divider=u_turn_backward are a bad idea.

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Re: [OSM-talk] Divided roads proposal

2009-12-03 Thread Lester Caine

Steve Bennett wrote:
 Why? Primarily as a landmark, I would think. The fact that there is a
 median strip is more important, relatively, than that there is a
 median strip which is 83cm wide, surfaced in terracotta pavers
 overgrown with moss...
 
 Anyway, to back up slightly here, the benefits of this proposal are:
 - much simpler and faster entry of minor divided roads
 - better rendering at little cost
 - cleaner data structure that better reflects what we're trying to map
 
 The downsides are:
 - less specificity of the width of the division
 
 Are there other downsides I'm missing? Could you explain the lack of
 generality argument - what cases can't it handle, and why is this
 important?

The basic decision has to be at what level you switch between macro and micro 
mapping. If the feature is so small, is there any need to describe it in a 
complex series of tags ( assuming lots of gaps down a short road )? As soon as 
you move to a mapping zoom that can display he fine detail, then an area detail 
is required anyway. One of the examples provided was a simple 'U' - with the 
detail provided, one assumes a continuous dividing structure, with one way 
movement around the whole length. If there are gaps in the divide, then those 
should be indicated, with links or additional tags, but if the divide is just 
the odd bollard then it would be better drawn as a single dead end road anyway? 
This is more than adequate for routing purposes, and any finer detail really 
needs the areas of all of the parts that make up the roadway?

At what point to you switch from 'dual carriageway' to 'divided road' ?

-- 
Lester Caine - G8HFL
-
Contact - http://lsces.co.uk/wiki/?page=contact
L.S.Caine Electronic Services - http://lsces.co.uk
EnquirySolve - http://enquirysolve.com/
Model Engineers Digital Workshop - http://medw.co.uk//
Firebird - http://www.firebirdsql.org/index.php

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Re: [OSM-talk] Divided roads proposal

On Fri, Dec 4, 2009 at 4:21 AM, Anthony o...@inbox.org wrote:
 And I think that's eventually where we're going.  The distance between
 the centerlines is only part of the equation, but I wouldn't want to
 throw that information away.  This is all moot, however, because I now
 understand that you have no intention of throwing that information
 away.  The old way of doing things would still be allowed, and in fact
 would not be deprecated, right?

Oh, of course. Sorry, I hadn't made that clear. :) In most cases, the
trade-off between extreme accuracy, and usability will lead to the
simpler divider=* tag. For more complex cases, or where the shape of
the individual lanes matters, I'd still make two individual ways.

 I think the biggest downside is that it creates two accepted ways to
 map the same thing.  Even that, I suppose, is not a problem, if we
 make it clear that the old way, which contains more information, is
 preferable.

I think it depends on the circumstance, and whether that information
is valuable. If the community feels strongly that duplicated roads are
better in most cases, then the divided tag will be marginalised to
only the smallest cases, like painted traffic islands. I suspect it
will become more popular than that, though.

 Your initial email suggested to me that this method of mapping was
 superior to the old one.  You made a statement, which I agree with,
 that the current practice of duplicating minor roads when there is a
 median strip [is] pretty unsatisfactory.  So I thought you were
 attempting to replace that current practice.

Well, put it this way: if this was implemented, I would duplicate far
fewer roads in future. I don't know if I would go around converting
existing ones, though. I do think it's superior for minor roads where
the division is a modern traffic-calming device.

 You've clarified that you're not, and it looks like a router/renderer
 would be safe ignoring these new tags, so I guess I don't object.

If a router ignores the tags, it will occasionally try and send you
through a barrier. If a renderer ignores them, then it might be hiding
important information from the consumer. But there are certainly
already plenty of divided roads which are not marked as such.

Oh yeah, I forgot to mention a big problem.  Using forward/backward
breaks when a way is reversed.  So divider=u_turn_forward and
divider=u_turn_backward are a bad idea.

Yeah I haven't really thought through the u_turn thing much. I think
it's awkward for the reason you describe. It's probably better to just
have a junction tag that indicates there is a physical gap, and use
turn restrictions if you don't want one direction using it. Or just
create two lanes, and put a one-way in the right spot.

Steve

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Re: [OSM-talk] Divided roads proposal

2009/12/3 Anthony o...@inbox.org

  Are there other downsides I'm missing?

 I think the biggest downside is that it creates two accepted ways to
 map the same thing.  Even that, I suppose, is not a problem, if we
 make it clear that the old way, which contains more information, is
 preferable.


no, I think this is a big con: there are (and will always be) people who
change the map to different schemes, sometimes also loosing information
(e.g. on talk-de it was recently reported that people delete separately
mapped cycleways and attach cycleway=track to the road, what is loosing
information (positional and inhebitance of tagging different maxspeeds,
surfaces, widths, etc.). If the new way is containing less information,
don't set it online.

cheers,
Martin
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Re: [OSM-talk] Divided roads proposal

On Thu, Dec 3, 2009 at 12:37 PM, Martin Koppenhoefer
dieterdre...@gmail.com wrote:
 2009/12/3 Anthony o...@inbox.org

  Are there other downsides I'm missing?

 I think the biggest downside is that it creates two accepted ways to
 map the same thing.  Even that, I suppose, is not a problem, if we
 make it clear that the old way, which contains more information, is
 preferable.

 no, I think this is a big con: there are (and will always be) people who
 change the map to different schemes, sometimes also loosing information
 (e.g. on talk-de it was recently reported that people delete separately
 mapped cycleways and attach cycleway=track to the road, what is loosing
 information (positional and inhebitance of tagging different maxspeeds,
 surfaces, widths, etc.). If the new way is containing less information,
 don't set it online.

That was my initial reaction.  But then I thought about all the other
situations where we have two accepted ways to map the same thing.  For
example, a building can be mapped as a point or an area.  One is more
detailed, but the other is acceptable if you don't have time for the
detail.

I don't know.  I read over the proposal again and I don't even get it,
actually.  Is the way supposed to be split before and after each
intersection?

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Re: [OSM-talk] Divided roads proposal

On Thu, Dec 3, 2009 at 12:38 PM, Steve Bennett stevag...@gmail.com wrote:
 Well, put it this way: if this was implemented, I would duplicate far
 fewer roads in future.

If it worked (and I really haven't delved into the details enough to
check), I might be convinced to add division information where I
otherwise wouldn't bother (because the current method of creating a
dual carriageway is a pain).

 I don't know if I would go around converting
 existing ones, though.

If you don't knowthat scares me.

 If a router ignores the tags, it will occasionally try and send you
 through a barrier.

For a U-turn?  Whether or not a U-turn is legal should probably be
treated as unknown by routers in most cases.  We're currently not
really mapping that at all.

OTOH, if you're talking about a left turn, I thought the point was
that this would be handled by turn restrictions just like would be
done currently.

 If a renderer ignores them, then it might be hiding
 important information from the consumer. But there are certainly
 already plenty of divided roads which are not marked as such.

Yeah, I see this as maybe a potential solution in between using a
single unmarked way and using a dual carriageway.  Although, looking
at the proposal, it doesn't look finished - something you seem to
admit yourself.

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Re: [OSM-talk] Divided roads proposal

On Fri, Dec 4, 2009 at 4:46 AM, Anthony o...@inbox.org wrote:
 I don't know.  I read over the proposal again and I don't even get it,
 actually.  Is the way supposed to be split before and after each
 intersection?

Maybe I should write up the proposal as I see it, but all I'm proposing is:

divider=* tag on ways that are divided, where * is probably one of line,
median, barrier.
junction=*something*, to indicate a gap in a divided road where another road
passes through it.

ie:
 |
=+=
 |

With junction=fourway or whatever at the +.


You could equally well implement the junction like this:


  |
=*+*=
  |

Where * is a node, + is a junction, - is a normal way, and = is a way marked
with divider=*.

Steve
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Re: [OSM-talk] Divided roads proposal

On Fri, Dec 4, 2009 at 4:54 AM, Anthony o...@inbox.org wrote:

 On Thu, Dec 3, 2009 at 12:38 PM, Steve Bennett stevag...@gmail.com
 wrote:
  Well, put it this way: if this was implemented, I would duplicate far
  fewer roads in future.

 If it worked (and I really haven't delved into the details enough to
 check), I might be convinced to add division information where I
 otherwise wouldn't bother (because the current method of creating a
 dual carriageway is a pain).


Exactly.



  If a router ignores the tags, it will occasionally try and send you
  through a barrier.

 For a U-turn?  Whether or not a U-turn is legal should probably be
 treated as unknown by routers in most cases.  We're currently not
 really mapping that at all.


I guess that's country specific. Here (Australia), u-turns are legal by
default. But I'm not sure why routing software would need to do u-turns in
general.



 OTOH, if you're talking about a left turn, I thought the point was
 that this would be handled by turn restrictions just like would be
 done currently.


I'll assume you're in a right-hand-side drive country? Let's take this
situation:

   B
   |
A==C

You're going from A to B. I'm saying that the router doesn't attempt to make
the turn because the way A-C is marked as divided=median, and there's
nothing at the intersection to overrule that. If left turns are possible
there, then the junction should be marked as a gap, or there should be a
section of non-divided at that point.

Turn restrictions are a pain to edit, so it's great that the router gets a
free hint here.


Yeah, I see this as maybe a potential solution in between using a
 single unmarked way and using a dual carriageway.  Although, looking
 at the proposal, it doesn't look finished - something you seem to
 admit yourself.


Yep, I didn't write that proposal, I just liked the ideas in it. I guess
tomorow I'll write up the summary of this discussion.

Steve
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Re: [OSM-talk] Divided roads proposal

(Weird, did this email not get sent before - so many emails going back
and forth. Oops.)


On Fri, Dec 4, 2009 at 4:37 AM, Martin Koppenhoefer
dieterdre...@gmail.com wrote:
 no, I think this is a big con: there are (and will always be) people who
 change the map to different schemes, sometimes also loosing information
 (e.g. on talk-de it was recently reported that people delete separately
 mapped cycleways and attach cycleway=track to the road, what is loosing
 information (positional and inhebitance of tagging different maxspeeds,
 surfaces, widths, etc.). If the new way is containing less information,
 don't set it online.

Well, I guess I agree with you, but that's a big if. And it's a
question of mapping practice, not of software functionality. There are
a few scenarios:

1) There is a divided road that has been carefully mapped out.
Converting this to a simple divided=* tag could lose information.
2) There is a divided road that has been sketched out roughly, simply
to indicate the division. (Very common, I think) Converting this to a
simple divided=* tag doesn't lose information, and better indicates
the actual level of information stored.
3) There is a divided road which is represented as a single road,
because it's not particularly important, or the mapper was lazy or
whatever. This could be a *gain* of information.

As an example of 3), see this randomly chosen spot:
http://www.openstreetmap.org/edit?lat=-37.747252lon=144.7879zoom=19

(Turn on nearmap to see the imagery). There's a corner with a brief
division as a safety device. You probably wouldn't map that as two
lanes, because it would look ugly and superfluous. But it would look
elegant with a simple divided=* tag.

Here's one that looks like 2):
http://www.openstreetmap.org/edit?lat=-37.77825lon=144.830416zoom=19

There are two lanes to indicate the divided highway, but the mapper
hasn't marked out the cut throughs, so this results in worse mapping
than if they'd just made a single road. - the router can't tell that
you can turn left across the median strip.

If you follow that road south a bit, you'll find cases of 3 and 2:
painted lines, some of which are marked as separate lanes, some
aren't. IMHO it would be cleaner to represent all of those with a
divided=* tag, but tthat's just my opinion.


http://www.openstreetmap.org/edit?lat=-37.77888lon=144.833565zoom=19

A clear example of 1: obviously you would not convert this massive
median strip into a single way.

http://www.openstreetmap.org/edit?lat=-37.786651lon=144.84961zoom=19

Another 1), I think. An interesting shaped median strip best left as two ways.

http://www.openstreetmap.org/edit?lat=-37.785579lon=144.854427zoom=19

But just a bit down the road, the median strip is very  uniform. It's
probably wide enough to justify the two lanes, but it's worth asking
the question.

http://www.openstreetmap.org/edit?lat=-37.791938lon=144.86358zoom=20

Also worth asking whether a traffic island is different from a short division.

Steve

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Re: [OSM-talk] Divided roads proposal

On Thu, Dec 3, 2009 at 12:58 PM, Steve Bennett stevag...@gmail.com wrote:
 ie:
      |
 =+=
      |

 With junction=fourway or whatever at the +.

fourway would be the only tag that's not ambiguous.  Your junction
was already solved properly by turn restrictions.
(http://wiki.openstreetmap.org/wiki/Relation:restriction)

divider=none, divider=legal, and divider=physical is about the only
part of that proposal that I'm fairly sure would work.

And divider=physical goes against current mapping principles.  As a
sort of todo tag, I guess it isn't horrible, though.
divider=physical meaning this should be a dual carriageway, but I
don't really feel like doing all the work of mapping it that way.

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Re: [OSM-talk] Divided roads proposal

On Thu, Dec 3, 2009 at 1:05 PM, Steve Bennett stevag...@gmail.com wrote:
 Let's take this situation:

        B
        |
 A==C

 You're going from A to B. I'm saying that the router doesn't attempt to make
 the turn because the way A-C is marked as divided=median, and there's
 nothing at the intersection to overrule that. If left turns are possible
 there, then the junction should be marked as a gap, or there should be a
 section of non-divided at that point.

So if I decide to split AC for whatever reason, I've just broken the routing?

Relations aren't that hard.  Not nearly hard enough to justify
something like this.  IMHO.

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Re: [OSM-talk] Divided roads proposal

2009/12/3 Richard Mann richard.mann.westoxf...@googlemail.com:
 Unless you want to write routines for pre-processing two almost-parallel
 ways back into a single way so it can be rendered neatly, I suggest it's a
 mapping problem. Don't make work for other people if you don't have to.

I thought we were trying to map the world in as much detail as
possible, just because they are almost parallel doesn't mean they
don't diverge etc.

I like the current way of doing things where if they are physically
seperated they should be drawn as 2 different ways, some even argue a
strong centreline is enough but I disagree on this point.

Also I was under the impression that turning restrictions are a
signage thing, not a physical barrier thing.

If the map doesn't render the data properly then it's a rendering
problem, otherwise we're just throwing away data because someone
thinks it will look nicer that way.

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Re: [OSM-talk] Divided roads proposal

Awesome, nice to finally get some proper criticism :)

I'll write up the proposal as I see it. I think most of these comments are
assuming that somehow a single divider=* tag is going to replace all split
roads, including dual carriageway motorways etc. That's not what I'm
suggesting.

I like the current way of doing things where if they are physically
 seperated they should be drawn as 2 different ways, some even argue a
 strong centreline is enough but I disagree on this point.


There's a good example of why a divider=* tag makes sense. Currently you
have two options: single road, or two separate roads. This is a good middle
ground for cases where the two separate roads strategy is too big and
heavy.



 Also I was under the impression that turning restrictions are a
 signage thing, not a physical barrier thing.


Not sure what you mean here. We're discussing three different types of
divider: those that are just legal/signed/marked, those where there is a
physical kerb but which could theoretically be driven over, and those with a
serious barrier that even a pedestrian would struggle with.

If the map doesn't render the data properly then it's a rendering
 problem, otherwise we're just throwing away data because someone
 thinks it will look nicer that way.


Again, this proposal is not primarily about rendering. That's a nice benefit
in some cases. The goals are:
1) More appropriate data structure
2) Better usability
3) Better rendering at no effort.

There may be other benefits too. And again, I'm mostly focused on the
situations where mapping as a single road is losing information, and mapping
as two roads is inappropriate/undesirable.

Steve
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Re: [OSM-talk] Divided roads proposal

2009/12/4 Steve Bennett stevag...@gmail.com:
 Again, this proposal is not primarily about rendering. That's a nice benefit
 in some cases. The goals are:
 1) More appropriate data structure

How is this more appropriate, you are loosing real world information
to improve rendering.

 2) Better usability

How does this improve useability at all?

 3) Better rendering at no effort.

Number 3 shouldn't be a goal, just like using the layer tag shouldn't
be used to alter the rendering order.

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Re: [OSM-talk] Divided roads proposal

On Fri, Dec 4, 2009 at 4:28 PM, John Smith deltafoxtrot...@gmail.comwrote:

 2009/12/4 Steve Bennett stevag...@gmail.com:
  Again, this proposal is not primarily about rendering. That's a nice
 benefit
  in some cases. The goals are:
  1) More appropriate data structure

 How is this more appropriate, you are loosing real world information
 to improve rendering.


The main focus is *adding* information to roads currently mapped as single
(non-divided) roads. Gaining information. Not losing. There are a huge
number of places that this will add information that was not previously
mapped.

I don't know how to convince you that I'm not proposing changing the way
major roads and dual carriageways are mapped. This is about minor divisions
in minor roads.

Let me ask you: how do you think that a road with a painted traffic island
down the middle should be mapped:
1) As a single road with no special tagging
2) As a single road with a tag indicating the division
3) As two separate ways, with ways connecting them every time there's a gap
in the painted division.

Here's an example that we can use to discuss (use satellite view):
*http://tinyurl.com/y8cxujs
**
*If you would like to propose some rules for the use of this tagging (like
don't use it for dual carriageways), that would be helpful.

 2) Better usability


 How does this improve useability at all?


Because adding a single tag is a lot simpler than making two parallel ways.
Because modelling one road as is easier than modelling one road as two
roads.

 3) Better rendering at no effort.

 Number 3 shouldn't be a goal, just like using the layer tag shouldn't
 be used to alter the rendering order.


Better rendering should always be a goal. What I think you mean is we
shouldn't modify the way we map in order to compensate for some short-term
deficiency in current renderers. I agree. I think modelling minor streets
that have median strips as single roads is the right thing to do. Better
rendering is just an additional benefit. If there was a trade-off between
them, we would go with correct modelling.

Steve
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Re: [OSM-talk] Divided roads proposal