On Sun, 27 Sep 2009 07:36:03 +0930 Jim Croft <jim.cr...@gmail.com> wrote:
> I had never really thought of this before, but land traveller and > mariner have quite different concepts of what it means to reach 'the > coast'. For the former it is when you get your feet wet, for the > latter it is when you run into something. And there are places where > there is quite a gap between the two. > > Given that OSM is a land-based project, the mean high water mark is > probably might be the best to use. > Where I've realigned the PGS data to sat images I've used the high water mark where it was discernable, otherwise as below. With the Yahoo images where I live (and most of the Qld coast north of Brisbane) that's not really practicable as they are not hires, in this case I've aligned it with the beach/vegetation line (where there is a beach or rocks) and the vegetation line where there is no beach. This is about as close as you are going to get it in this situation. The PGS data is an approximation of the High Water Mark not the mean high water mark see here: http://www.nga.mil/portal/site/nga01/index.jsp?epi-content=GENERIC&itemID=9328fbd8dcc4a010VgnVCMServer3c02010aRCRD&beanID=1629630080&viewID=Article Using gpsdrive it's possible to add the SRTM (contour data) and ocean depth data to overlay the osm data and display a usable coastline (not for navigation though yet). -- Cheers Ross _______________________________________________ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
