I have a city "map" (for example - Moscow). She in accuracy repeats the contours the given city in google maps (that is it is copied from google maps and it is a little processed, but the sense remained the same).

Also I have object co-ordinates in a city (in co-ordinates of google).

Problem: how to convert google co-ordinates to the co-ordinates of my picture (that is in pixels on OX and OY on a picture). That is I receive google-co-ordinates and it is necessary for me to draw this point on my picture.

The most desired variant of the answer - is based on javascript, but it is possible and on php.

I know that on small scales (for example on city scales) it to make simply enough (it is necessary to learn what google-co-ordinates has one of picture corners, then to learn "price" of one pixel in google-co-ordinates on a picture on axes OX and OY separately).

But on the big scales (country scale) "price" of one pixel will be not a constant, and will vary strongly enough and the method described above cannot be applied.

How to solve a problem on country scales?