Rather than having polygons/shapefiles for everywhere, you could just have them for the exceptions to the rule that altitude servers consider the oceans to be at sea level.
That would mean having shapes for things like inland seas and the Great Lakes, remembering that they are water even though they're above sea level. I don't think you need to have shapes for land that's below sea level. The US Geological Survey Elevation server never seems to actually return zero for land - it seems to jump from -1 metres to +1 metres as you approach sea level land. You might possibly get away with detecting lakes and inland seas by checking the altitudes of a few nearby points. If the altitudes of the points vary, then you're looking at land. If the altitudes are all exactly the same, then it may be water. It may work for large rivers, like the Thames below Battersea. When HTML5 comes, it may be possible to obtain the URL of a tile, place a copy of the image tile into a <canvas> and use context.getImageData to read the colours of the pixels from the <canvas>. However, not all of the compatible browsers intend to support HTML5. -- http://econym.org.uk/gmap The Blackpool Community Church Javascript Team --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Google Maps API" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/Google-Maps-API?hl=en -~----------~----~----~----~------~----~------~--~---
