I've implemented a Java version of the C# SDK sample "PointConversion" which works great for almost all uses. The algorithms seem to break down, however, with maps viewed from such a "height" that the curvature of the Earth shows on the map (including black areas of "outer space").

When I use Microsoft Streets & Trips (el cheapo MapPoint client) with it's Location Sensor activated, it correctly shows LAT/LON for these "outer space" areas as "Unknown" but the "PointConversion" algorithm provided with the SDK doesn't seem to handle this. When passed a LAT/LON which should not be visible on the map (because it's beyond the horizon) the algorithm returns the proper X,Y coordinate (but ONLY if the Earth were transparent!) It doesn't seem to be able to indicate that the LAT/LON isn't visible on the map.

Can you offer any suggestions as to how to prevent this? Can you shed some light on how Streets & Trips (or the MapPoint desktop client) handle this so I can incorporate it into my use of the MapPoint Web Service?

Thanks!

Do you have the longitude and latitude of the view point?

If so, you could compare the coordinate that you are interested in and compare it with the viewpoint. If they are separated by 90 degrees or more, then it is on the other side of the Earth.

The following site has some calculations that could probably be adapted to make the comparison:

http://williams.best.vwh.net/avform.htm


Richard

Great suggestion. Works like a champ. Thanks!