orthographic Projection

Hi Friends

I need to implement orthographic Projection over an image generated by Mappoint webservice.

I am using the equations found on
Orthographic projection (cartography) - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Orthographic_projection_%28cartography%29)

but it seems that it is not working. My first question is what is the value of the earth radius to be used in these equations? Must it be in m, km or other units?

any help is really appreciated.

regards

You can use any convenient units for R, as long as the same units are used for x and y. The angles have to be consistent as well, and have to be in radians for most programming use. Note the statement about the atan2 function; an atan function that doesn't take account of the quadrant of the input values for returning the right sign of the result will cause the map to fold on top of itself.