----- Original Message ----- From: "Cartinus" <[EMAIL PROTECTED]> To: <talk@openstreetmap.org> Sent: Monday, April 14, 2008 10:24 PM Subject: Re: [OSM-talk] Rocky beaches
> Lots of coastline in OSM comes from PGS data. According to > http://wiki.openstreetmap.org/index.php/PGS_whitepaper > > "This new shoreline is an approximation of the High Water Line; it is NOT > a > Mean High Water Line since the source data have not been tide > coordinated." > > This of course says nothing about other coastline data. > > Dutch topographic maps don't consider tidal flats a part of the land. It > is > coloured the same colour blue as the sea, but it has lots of black dots in > it. > > -- > m.v.g., > Cartinus > The approach I have been taking is to tag natural=coastline as an approximation of high water. Any area of sand which is normally above the high water mark I have tagged as natural=beach. To tag the coastline as the low water line would I believe in many instances give an outline which would not be recognisable to most people as "the coast". As an example see the area to the North-East of Ryde, Isle of Wight, UK [1]. On the low-res Yahoo image you can see a spit of light yellow / green extending over 1 Km from the marked coast. This is Ryde Sands, a sandbank which is uncovered at low water. Had I used the outline of this to tag natural=coastline it would have resulted in the outline of the Isle of Wight including this sandbank, and would not have been anything like what anyone would expect a "map" of the Isle of Wight to look like at low zoom levels. I'm currently not tagging anything below the high water mark, because I hadn't felt there was an appropriate approved tag. I guess what I would argue is natural=coastline should be tagged as the high water line (so the outline of the coast looks 'correct' at low zoom) and that features below high water be marked as a separate layer, rendered on top of the blue for the water at higher zoom levels. David [1] www.openstreetmap.org/edit.html?lat=50.7346&lon=-1.1201&zoom=13 _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
