Hi David, Mangroves and wetlands have been discussed here in 2009 and 2010 but no definite convention or guidelines was agreed upon. Please see the following two threads for the previous discussions:
https://lists.openstreetmap.org/pipermail/talk-ph/2009-April/000695.html https://lists.openstreetmap.org/pipermail/talk-ph/2010-July/002398.html Based on agreed practice in OSM, the natural=coastline is defined to be the high water line. So mangrove areas would be normally at the seaward side of OSM's coastlines. But I think the answer is between your approach 1 and 2. Mangroves can actually extend to the land-side of the coastline as the ground there would still be saturated with sea water even if the ground is not submerged at high tide. The problem is, the high-water line will rarely be visible on satellite imagery. So I think we just map using approach 2 when doing remote/armchair mapping and then hope that these can be refined in the future using actual field surveys. Regards, Eugene On Sat, Apr 30, 2016 at 10:14 AM, David Groom <[email protected]> wrote: > There are two different approaches used in mapping mangrove areas in OSM > > 1) Treat the boundary of the mangrove and the openwater sea as the > coastline, and then map the area between that line and the "dry" land as > wetland. This means that the wetland symbols are rendered over the white > colour of the land, and that at zoom levels 12 and lower the mangrove areas > simply get shown as white, with the sea outside them. > > 2) Treat the boundary of the mangrove and the "dry" land as the > coastline, and then map the area between that line and the openwater sea as > wetland. This means that the wetland symbols are rendered over the blue > colour of the sea, and that at zoom levels 12 and lower the mangrove areas > simply get shown as blue sea. > > Early today I added some mangrove areas and followed approach 2 because > the coastline had been accurately mapped along the mangrove / dry land > boundary, as so I simply added the mangrove area outside this, as it seemed > the existing mapper had cleary thought the coastline should be at the dry > land boundary. > > However at http://www.openstreetmap.org/#map=14/9.7497/125.6105 both > these approaches have been used. Approach 1 has been used for Lamagon > Island, where the boundary of the mangrove area and the sea is tagged as > coastline. But Approach 2 has been used for the island immeditately south, > where the boundary of the dry land is tagged as coastline. > > On further investigation I see at > http://www.openstreetmap.org/#map=14/9.7003/125.6415 that Approach 1 has > been used. > > Has this issue been discussued before within the Philippine OSM community, > with any recommended way of mapping mangrove areas being decided upon? > > Regards > David > > > > _______________________________________________ > talk-ph mailing list > [email protected] > https://lists.openstreetmap.org/listinfo/talk-ph >
_______________________________________________ talk-ph mailing list [email protected] https://lists.openstreetmap.org/listinfo/talk-ph
