Change the coordinate system of a Canvas in WPF

Question

I\'m writing a mapping app that uses a Canvas for positioning elements. For each element I have to programatically convert element\'s Lat/Long to the canvas\' coordinate, then

Answer 1

I'm pretty sure you can't do that exactly, but it would be pretty trivial to have a method which translated from lat/long to Canvas coordinates.

Point ToCanvas(double lat, double lon) {
  double x = ((lon * myCanvas.ActualWidth) / 360.0) - 180.0;
  double y = ((lat * myCanvas.ActualHeight) / 180.0) - 90.0;
  return new Point(x,y);
}

(Or something along those lines)

Answer 2

Another possible solution:

Embed a custom canvas (the draw-to canvas) in another canvas (the background canvas) and set the draw-to canvas so that it is transparent and does not clip to bounds. Transform the draw-to canvas with a matrix that makes y flip (M22 = -1) and translates/scales the canvas inside the parent canvas to view the extend of the world you're looking at.

In effect, if you draw at -115, 42 in the draw-to canvas, the item you are drawing is "off" the canvas, but shows up anyway because the canvas is not clipping to bounds. You then transform the draw-to canvas so that the point shows up in the right spot on the background canvas.

This is something I'll be trying myself soon. Hope it helps.