Re: [talk-au] natural=land v natural=coastline
2009/10/6 Ross Scanlon i...@4x4falcon.com: On Tue, 6 Oct 2009 15:32:49 +1000 John Smith deltafoxtrot...@gmail.com wrote: Lake Gairdner and Lake Torrens are natural=coastline Well there both now natural=water as they are both single ways less than 1000 nodes and there's no need for them to be natural=coastline. Since the number of nodes is so low I can only guess it may have been a tagging mistake or was intentional to get it to render at z5 or lower... Also Lake Eyre renders for me at z6 on maps.bigtincan.com... The other lakes render before that, up to z2... ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] natural=land v natural=coastline
I just updated all the world boundaries and shore lines etc on maps.bigtincan.com and this is the dates of files: -rw-r--r-- 1 1001 1001 3461233 Mar 10 2007 builtup_area.dbf -rw-r--r-- 1 1001 1001279020 Mar 10 2007 builtup_area.index -rw-r--r-- 1 1001 1001 513 Mar 10 2007 builtup_area.prj -rw-r--r-- 1 1001 1001 13378292 Mar 10 2007 builtup_area.shp -rw-r--r-- 1 1001 1001291556 Mar 10 2007 builtup_area.shx -rw-r--r-- 1 1001 1001 15440 Mar 10 2007 places.dbf -rw-r--r-- 1 1001 1001 333 Mar 10 2007 places.prj -rw-r--r-- 1 1001 1001 7128 Mar 10 2007 places.shp -rw-r--r-- 1 1001 1001 2108 Mar 10 2007 places.shx -rw-r--r-- 1 root root 4587079 Oct 6 00:20 processed_p.dbf -rw-r--r-- 1 root root 2139804 Oct 6 00:21 processed_p.index -rw-r--r-- 1 root root 410634792 Oct 6 00:20 processed_p.shp -rw-r--r-- 1 root root 3669660 Oct 6 00:20 processed_p.shx -rw-r--r-- 1 1004 1004 3078665 Oct 3 12:58 shoreline_300.dbf -rw-r--r-- 1 1004 1004 1332456 Oct 3 12:58 shoreline_300.index -rw-r--r-- 1 1004 1004 89770164 Oct 3 12:58 shoreline_300.shp -rw-r--r-- 1 1004 1004 2052500 Oct 3 12:58 shoreline_300.shx -rw-r--r-- 1 1001 1001 4145601 Mar 9 2007 world_bnd_m.dbf -rw-r--r-- 1 1001 1001250968 Sep 10 2007 world_bnd_m.index -rw-r--r-- 1 1001 1001 355 Mar 9 2007 world_bnd_m.prj -rw-r--r-- 1 1001 1001 48495316 Mar 9 2007 world_bnd_m.shp -rw-r--r-- 1 1001 1001249444 Mar 9 2007 world_bnd_m.shx -rw-r--r-- 1 1001 1001673969 Mar 31 2008 world_boundaries_m.dbf -rw-r--r-- 1 1001 1001 86700 Mar 31 2008 world_boundaries_m.index -rw-r--r-- 1 1001 1001 355 Mar 31 2008 world_boundaries_m.prj -rw-r--r-- 1 1001 1001 6669352 Mar 31 2008 world_boundaries_m.shp -rw-r--r-- 1 1001 1001 30556 Mar 31 2008 world_boundaries_m.shx I think the processed_p files are coastlines, z10- I think. ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] natural=land v natural=coastline
On 06/10/2009, at 2:12 PM, John Smith wrote: Lake Eyre etc is so big they used natural=coastline... Although this comes back to the question the other day, where does the coastline start/end, legally speaking it cuts across bays, it doesn't go round them or up rivers... I looked into this a while back and it's somewhat contentious. The best I could figure out (which is quite possibly wrong) is that a coastline ends and a river starts when there are no longer any tidal significant effects. It's easiest to see if you have a slope, such as a sandy beach. Consider the following, where at some point the high and low tide levels get close enough to be negligable 1 sand 2 high tide ---\ 3 sand / water -- 6 4 low tide --- / 5 water (1) is a polygon with natural=beach;surface=sand (2) is the way with natural=coastline (3) is a polygon with water=tidal;surface=sand (6) is waterway=riverbank At the point where it changes from coastline to riverbank, you obviously need to have the coastline run across the river, so as to form closed shape. Whether you're supposed to have the riverbank do the same to form a closed shape, I don't know. ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] natural=land v natural=coastline
2009/10/6 James Livingston doc...@mac.com: On 06/10/2009, at 2:12 PM, John Smith wrote: Lake Eyre etc is so big they used natural=coastline... Although this comes back to the question the other day, where does the coastline start/end, legally speaking it cuts across bays, it doesn't go round them or up rivers... I looked into this a while back and it's somewhat contentious. The best I could figure out (which is quite possibly wrong) is that a coastline ends and a river starts when there are no longer any tidal significant effects. It's easiest to see if you have a slope, such as a sandy beach. Consider the following, where at some point the high and low tide levels get close enough to be negligable I realise this is potentially a very contensious issue. If you look at this from the point of view of territorial waters the coastline is from either the high or low tide marks, they spell it out in legalese and I can't remember off the top of my head, but the coast line cuts across any river/delta/bay mouths, except where the bay is partially inhabited by another country and then it's usually by seperate agreement. I honestly don't know which way is best to go here, since all definitions are reasonably subjective and would also depend on average tide conditions and so on and so forth. Another way we could look at this is to find out where salt and fresh water mix, but this too is probably tide and rainfall related. We also have the SRTM data which could be used to estimate elevation of water above mean sea levels, which would also depend on tide/rainfall at the time the STRM mission flew. At the point where it changes from coastline to riverbank, you obviously need to have the coastline run across the river, so as to form closed shape. Whether you're supposed to have the riverbank do the same to form a closed shape, I don't know. Actually it's the opposite, coastlines aren't really closed ways as there is no single coastline polygon or multipolygon, riverbanks on the other hand must be closed and must be either less than 2000 nodes or have a multipolygon relation. ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] natural=land v natural=coastline
For OSM purposes (as opposed to general mapping) the answer should not
be complicated. If at high tide you drive into the water, you have
driven over a functional coast into the sea... :)
Of course, this won't work for mariners and lawyers... :)
My favourite estuary is the Fly River in PNG. It just gets gradually
wider and wider and wider. Somewhere the river becomes the ocean.
And there is no way to tell where it happens...
jim
On Tue, Oct 6, 2009 at 11:35 PM, John Smith deltafoxtrot...@gmail.com wrote:
2009/10/6 James Livingston doc...@mac.com:
On 06/10/2009, at 2:12 PM, John Smith wrote:
Lake Eyre etc is so big they used natural=coastline... Although this
comes back to the question the other day, where does the coastline
start/end, legally speaking it cuts across bays, it doesn't go round
them or up rivers...
I looked into this a while back and it's somewhat contentious. The
best I could figure out (which is quite possibly wrong) is that a
coastline ends and a river starts when there are no longer any tidal
significant effects. It's easiest to see if you have a slope, such as
a sandy beach. Consider the following, where at some point the high
and low tide levels get close enough to be negligable
I realise this is potentially a very contensious issue.
If you look at this from the point of view of territorial waters the
coastline is from either the high or low tide marks, they spell it out
in legalese and I can't remember off the top of my head, but the coast
line cuts across any river/delta/bay mouths, except where the bay is
partially inhabited by another country and then it's usually by
seperate agreement.
I honestly don't know which way is best to go here, since all
definitions are reasonably subjective and would also depend on average
tide conditions and so on and so forth.
Another way we could look at this is to find out where salt and fresh
water mix, but this too is probably tide and rainfall related.
We also have the SRTM data which could be used to estimate elevation
of water above mean sea levels, which would also depend on
tide/rainfall at the time the STRM mission flew.
At the point where it changes from coastline to riverbank, you
obviously need to have the coastline run across the river, so as to
form closed shape. Whether you're supposed to have the riverbank do
the same to form a closed shape, I don't know.
Actually it's the opposite, coastlines aren't really closed ways as
there is no single coastline polygon or multipolygon, riverbanks on
the other hand must be closed and must be either less than 2000 nodes
or have a multipolygon relation.
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... 'All is leaf' ('Alles ist Blatt') - Goethe
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Re: [talk-au] natural=land v natural=coastline
On 06/10/2009, at 11:37 PM, Jim Croft wrote: Of course, this won't work for mariners and lawyers... :) No, but there are (proposed) tags to indicate the low-tide mark, and the OpenSeaMap guys might have something for other various maritime boundaries. My favourite estuary is the Fly River in PNG. It just gets gradually wider and wider and wider. Somewhere the river becomes the ocean. And there is no way to tell where it happens... Yep, the problem with saying where the tidal effect are no longer significant or where fresh and sea water meet is that they're continuous, so you need some arbitrary limit. I'd say the only definite boundary would be to take the convex hull of the land mass. Of course, that means the Great Australian Bight would be a river, along with the Gulf of Carpentaria and the similar places and the like. ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] natural=land v natural=coastline
2009/10/6 John Smith deltafoxtrot...@gmail.com: If you look at this from the point of view of territorial waters the coastline is from either the high or low tide marks, they spell it out in legalese and I can't remember off the top of my head, but the coast line cuts across any river/delta/bay mouths, except where the bay is partially inhabited by another country and then it's usually by seperate agreement. Then they start arguing over how wide the bay has to be before it stops becoming territorial waters. Libya has tried to claim the entire indentation on it's coast (about 500 miles across) as a bay, and therefore territorial waters. Pretty much everybody else disagreed, and occasionally shots were fired over it. But I don't think we need to worry about this territory line, for our coastline purpose. We're more worried about were the sea starts and ends, not where a country does. Stephen ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
[talk-au] natural=land v natural=coastline
I've noticed lots of the islands off the Queensland coast have had their coastlines changed to natural=land. From the wiki this is incorrect. natural=land is for Land that exists within another area, such as a lake. additionally look here: http://wiki.openstreetmap.org/wiki/Tag:natural%3Dcoastline Without natural=coastline the islands will not show up in the coastline shape file. I have corrected all the islands between Mackay and Bowen. -- Cheers Ross ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] natural=land v natural=coastline
They will render still. Depends. Look at informationfreeway.org for this area at zooms less than 12 and you will see that most of the islands are missing. The roads on Hamilton Island are in the middle of the water. -- Cheers Ross ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
[talk-au] natural=land v natural=coastline
On Tue, 6 Oct 2009 14:22:59 +1000 John Smith deltafoxtrot...@gmail.com wrote: 2009/10/6 Ross Scanlon i...@4x4falcon.com: They will render still. Depends. Look at informationfreeway.org for this area at zooms less than 12 and you will see that most of the islands are missing. The roads on Hamilton Island are in the middle of the water. I'm guessing t...@h is wrong, mapnik renders them. Depends on the implementation of mapnik. If you tell mapnik to use the coastlines from the shape file it won't render them. -- Cheers Ross ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] natural=land v natural=coastline
On Tue, 6 Oct 2009 14:26:50 +1000 John Smith deltafoxtrot...@gmail.com wrote: 2009/10/6 Ross Scanlon i...@4x4falcon.com: On Tue, 6 Oct 2009 14:22:59 +1000 John Smith deltafoxtrot...@gmail.com wrote: 2009/10/6 Ross Scanlon i...@4x4falcon.com: They will render still. Depends. Look at informationfreeway.org for this area at zooms less than 12 and you will see that most of the islands are missing. The roads on Hamilton Island are in the middle of the water. I'm guessing t...@h is wrong, mapnik renders them. Depends on the implementation of mapnik. If you tell mapnik to use the coastlines from the shape file it won't render them. ummm? Have a read of this: http://wiki.openstreetmap.org/index.php/Coastline -- Cheers Ross ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] natural=land v natural=coastline
2009/10/6 Ross Scanlon i...@4x4falcon.com: On Tue, 6 Oct 2009 14:26:50 +1000 John Smith deltafoxtrot...@gmail.com wrote: 2009/10/6 Ross Scanlon i...@4x4falcon.com: On Tue, 6 Oct 2009 14:22:59 +1000 John Smith deltafoxtrot...@gmail.com wrote: 2009/10/6 Ross Scanlon i...@4x4falcon.com: They will render still. Depends. Look at informationfreeway.org for this area at zooms less than 12 and you will see that most of the islands are missing. The roads on Hamilton Island are in the middle of the water. I'm guessing t...@h is wrong, mapnik renders them. Depends on the implementation of mapnik. If you tell mapnik to use the coastlines from the shape file it won't render them. ummm? Have a read of this: http://wiki.openstreetmap.org/index.php/Coastline Anything big enough to appear on z9 is most likely going to have more than 2000 nodes... ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] natural=land v natural=coastline
Have a read of this: http://wiki.openstreetmap.org/index.php/Coastline Anything big enough to appear on z9 is most likely going to have more than 2000 nodes... That's one reason to use the shape files for the coastlines and if it's not tagged as natural=coastline when the shape files are regenerated then the island(s) will disappear. -- Cheers Ross ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] natural=land v natural=coastline
2009/10/6 Ross Scanlon i...@4x4falcon.com: Have a read of this: http://wiki.openstreetmap.org/index.php/Coastline Anything big enough to appear on z9 is most likely going to have more than 2000 nodes... That's one reason to use the shape files for the coastlines and if it's not tagged as natural=coastline when the shape files are regenerated then the island(s) will disappear. Only at z0-9, at least according to the wiki link you posted, not sure what happens after that, but natural=land will show up at z10- ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] natural=land v natural=coastline
Only at z0-9, at least according to the wiki link you posted, not sure what happens after that, but natural=land will show up at z10- There are three shape files that can be used, which cover all zoom levels. They are world_boundaries, coastlines and shorelines. Also just looking at Lake Eyre it is tagged as natural=water. -- Cheers Ross ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] natural=land v natural=coastline
Sorry, the 2 below it, if you zoom in to z10 you can see where Lake Eyre appears and at z9 it disappears. Interesting, on openstreetmap.org Lake Eyre appears from z6 whereas on bigtincan its from z9, so depends on how your osm.xml file is setup for mapnik. -- Cheers Ross ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] natural=land v natural=coastline
On Tue, 6 Oct 2009 15:32:49 +1000 John Smith deltafoxtrot...@gmail.com wrote: Lake Gairdner and Lake Torrens are natural=coastline Well there both now natural=water as they are both single ways less than 1000 nodes and there's no need for them to be natural=coastline. -- Cheers Ross ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
