I would like to know if it is possible to calculate the geographic coordinates (lat, lon) for a pixel specified by its x/y (top-left) cartesian coordinates in a map image/raster?

The datum and projection are known: WSG84/EPSG4326 , as the envelope/extent (4 "corners" + the center point).

It seems the goal is somewhat similar to the one of gdallocationinfo, but I don't find the way to indicate the map extent/bbox.

If possible, tools from GDAL or GeographicLib can be used.

I can't find the related formula.

1 Answer 1


What you need is affine transformation and it should be easy to do with Python:

You'll need GDAL GeoTransform (and it seems like you have all you need for it):

gt[0] /* top left x */
gt[1] /* w-e pixel resolution */
gt[2] /* 0 */
gt[3] /* top left y */
gt[4] /* 0 */
gt[5] /* n-s pixel resolution (negative value) */

And then having your x,y:

geo_x = gt[0] + (x+0.5) * gt[1] + (y+0.5) * gt[2]
geo_y = gt[3] + (x+0.5) * gt[4] + (y+0.5) * gt[5]

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