Re: [Talk-GB] Motorway junctions where the slow lane seperates from the through lanes
Hi
I would suggest that the motorway should not be split until the point
where the two halves physically diverge; instead, where there's a drop
lane, use turn:lanes and destination:lanes tags to indicatethe presence
of the drop lane.
My reasoning for this:
- firstly, there's no physical separation between the drop lane and the
main line of the motorway, and it's still physically and legally
possible to change between the two, and
- secondly, splitting a motorway based on different lanes having
different destinations sets an awkward pattern, which taken to extremes
means we end up splitting roads all over the place based on lane
markings. Sometimes that's necessary to make routing work sensibly
through complex junctions, but I'd argue that this isn't one of those cases.
Best illustrated with examples:
Drop lane starts here. Before this point, a single way with lanes=3.
After this point, still a single way, with lanes=3,
turn:lanes=slight_left|through|through :
https://www.mapillary.com/app/?pKey=v4H-uhxh9QQYjzL1b_BNMg=photo
The drop lane then runs for 300 metres, where there's no physical (or
legal) barrier between the lanes, so still a single way with lanes=3,
turn:lanes=slight_left|through|through :
https://www.mapillary.com/app/?pKey=S-dGYQdsR7olODRufbB5bg=photo
Then the actual split, where first there's a legal barrier (solid white
paint), then a physical one (grass, barrier, trees, hillside, etc):
https://www.mapillary.com/app/?pKey=1WY5HbP5K-vpUnAT0voYGw=photo
It's here where I'd suggest we'd split into highway=motorway_link,
lanes=1 (lanes=2 shortly thereafter), and highway=motorway, lanes=2,
with a shortish Y-shaped transition to make it look sensible. Of
course, at this point the main line of the motorway loses the turn:lanes
tag, and you can then add turn:lanes tags to the slip road as it widens
out for the roundabout at the end. The middle point of the Y (and not
the start of the drop lane) carries the highway=motorway_junction and
associated tags.
You could also add destination:lanes tags to label up the signed
destinations, and destination:ref:lanes=A4174|M32|M32.
Incidentally, for me, /this/ is the sort of situation justifying
separate, parallel ways on a motorway:
https://www.mapillary.com/app/?pKey=AL0RC-DyWe27PMQEAS1uZA=photo
TL;DR? Don't split based on lane markings, it's not a 300-metre-long
physically separate way, it's just a lane with a different destination.
Instead use turn:lanes, destination:lanes and destination:ref:lanes tags
to indicate the drop lane.
Cheers,
Paul ("southglos")
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Re: [Talk-GB] Estimating coverage
Hi Nice work! The area figures are obviously including the wet bits. Bristol is half water: http://news.bbc.co.uk/1/hi/england/bristol/7019663.stm I also notice the OSM motorway figures are generally a fair bit above the official figures - slip roads? Cheers Paul (southglos) -Original Message- Date: Tue, 11 Aug 2009 10:55:31 +0100 From: Peter Reed peter.r...@aligre.co.uk Subject: [Talk-GB] Estimating coverage I thought that comparing the area enclosed by the admin boundary on OSM with the area published by national statistics would be a good indicator of whether the boundary was accurate. In practice it works sometimes, but not others. I think this is mainly because of how the coastline and estuaries are handled in different places. Bristol is the extreme -the government thinks it is about twice as big as the area included in the boundary on OSM. ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
Re: [Talk-GB] Counties and coasts
Bristol (City and County) has an interesting boundary - it follows the bank of the River Avon out to the Severn estuary, then takes a large strip out of the Bristol Channel down to a pair of islands beyond Cardiff and Weston-s-M. Seems that the water off the shore of a fair bit of North Somerset belongs to Bristol. A BBC news article about it here: http://news.bbc.co.uk/1/hi/england/bristol/7019663.stm I traced the boundary from NPE some time ago based on this, but I notice that since then someone has redone the Bristol boundary and has removed the relevant ways, chopping back the water boundary to the end of the Avon. Paul (southglos) -Original Message- Date: Mon, 22 Jun 2009 14:45:55 +0100 From: Chris Hill chillly...@yahoo.co.uk Subject: [Talk-GB] Counties and coasts To: Talk GB talk-gb@openstreetmap.org Message-ID: 4a3f8b13.20...@yahoo.co.uk I'm interested the relations of the boundaries for counties. I notice that some counties (and recently English Regions) include the way for the coastline (natural=coastline), and some coastal counties do not. I think that coastal counties would benefit from a way to close the boundary, but does it make sense to use the coastline? The coastline way probably indicates cliffs or a sea wall, yet there is often some beach or tidal flats beyond this on the seaward side. I understand that councils are responsible for the beach so the county could be said to extend beyond what we currently mark as the coastline. Does anyone know where council boundaries actually end with respect to the sea and coastline? Cheers, Chris ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
Re: [Talk-GB] maxspeed field - what units should we use. etc
Hi I think the principle of keeping it easy for the mapper should apply. In the UK, speeds are signed in mph, and most mappers will think in mph, so let's record speeds in mph. Anything else leads to confusion, conversions, varying degrees of accuracy. But to my mind, the worst result is the inability to spot errors. For example, a stretch of ring road near me has various speed limits at various sections. I could tell you it's 50mph for the first bit, 30mph at the roundabout, then 70mph beyond. But when I looked at it recently, different bits were marked up with a whole jumble of numbers (including 112 on one side of the dual carriageway, 113 on the other). Yes, I can convert from km/h to mph and back again, but not in a quick glance. When I map in France, I tag in km/h (just using a bare number), but in the UK I absolutely want to tag in mph. From a data consumer's point of view, it's not hard to take any fields with mph at the end and preprocessing or converting on the fly, as long as there's consistency in using an 'mph' suffix. Seeing as there are more bare numbers that are obviously km/h than mph, saying a bare number in the UK should be interpreted as mph is asking for trouble, I think. So, I think maxspeed=30mph or maxspeed=48 should both be acceptable and equivalent, but maxspeed=30mph preferred in the UK. maxspeed=30 should NOT be used. One word of caution when looking at the tag usage in the UK - I've had swathes of my maxspeed tagging changed from mph to km/h by users (or their bots) in Germany and elsewhere, so beware using the current usage list as a measure how UK mappers want to tag. Keep it simple for the mapper and tag what's on the signs, and use an mph suffix to avoid confusion. Paul (southglos) -Original Message- Date: Thu, 4 Jun 2009 08:45:20 +0100 From: Peter Miller peter.mil...@itoworld.com Subject: [Talk-GB] maxspeed field - what units should we use. etc I have been looking at the coverage of maxspeed limit data for highways in the UK and we seem to have a right mix of styles. Here is the data for bug chunk of England while avoiding including anything from France or Ireland (which would include km/hour figure). We current have over 17,000 highway ways tagged with maxspeed and also 300 ways tagged as 'maxspeed:mph'. You will notice that for 30 miles per hour we have 30, 30mph, 30 mph, 48.2, 48.28, 48.280, 48.27808, 48.28032 and 48.28. Any suggestion on what we should recommend for the UK? I guess the USA should also be party to this discussion but they have far less population of the maxspeed field (only 70 uses in the Bay area) so possibly we should come to a view first. Our options seem to be:- maxspeed=30mph (the user should strip a trailing mph to find the value) maxspeed=30 (leaving it for the user to realise that it is in the UK and therefore imperial) maxspeed=30 mph (the user should strip the last word if it is mph including the space) maxspeed:mph=30 (Easy for the user) maxspeed=48.28 (with a defined precision) For metric use no work by the user, for imperial use a look-up table is required or a conversion and rounding ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
[Talk-GB] FW: BBC 'Britain From Above'
Interesting clip from the BBC: http://news.bbc.co.uk/1/hi/technology/7539529.stm It's a plug for a programme, 'Britain From Above', which starts 10th August, but the trailer alone is worth watching for some lovely GPS-derived visualisations. Paul (aka southglos) ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk-gb
