Convert mouse position to langtitude-longitude on a map

[Johnkokk]

OK, let's say i have this map loaded on a form http://upload.wikimedia.org/wikipedia/commons/9/92/Satellite_image_of_Greece.jpg[^]. Is there a way to convert the mouse position on that map as i move, to latitude and longitude ? If no, how such a thing can be done ? Thanks.

[Steven J Jowett]

If you know the coordinance of the top-left and the bottom-right, then it's down to basic maths to calculate the coordinance that the mouse is pointing to.

Steve Jowett ------------------------- Real programmers don't comment their code. If it was hard to write, it should be hard to read.

[David Skelly]

One thing to be aware of is that a map is a projection of a three dimensional curved surface onto a two dimensional plane, and there are different ways of handling that projection. So in order to convert the mouse position to a latitude/longitude on the map you need to know the projection in use for this particular map. In this case, it's not really a map, it's a satellite photograph. I have no idea how the maths works for mapping a 2D digital photograph back to the corresponding real-world position on the surface of a sphere. In fact the world is an oblate spheroid, I think, not a perfect sphere but you could probably make things easy by assuming a sphere and still be close enough for most practical purposes unless you're planning to write your own cruise missile guidance system.

[Steven J Jowett]

David Skelly wrote:

unless you're planning to write your own cruise missile guidance system.

Well actually..... ;)

Steve Jowett ------------------------- Real programmers don't comment their code. If it was hard to write, it should be hard to read.