# SAR calculating distance between 2 points

I am playing around with ESA's SNAP software and Sentinel-1 data and I was curios if it is possible to measure the ground distance between 2 points in a radar image. For example let's say that I am looking at radar image and I want to measure the distance (in meters) between the starting point a1(1000,1000) and ending point a2(1500,1600).

The way I would normaly do this is to get the pixel distance between the 2 points both for the range and azimuth directions, then multiply each dimension by its resolution per pixel, and finally use the Pythagoras theorem to get the magnitude of the produced vector which will give me the distance. In other words: X = 1500 - 1000 = 500 px Y = 1600 - 1000 = 600 px

Res_x = 5m (example value) Res_y = 10m (example value

Distance between a1 and a2 = sqrt((x * Res_x)^2 + (y * Res_y)^2)

However in the case of radar, this would not be true, since the radar is a side-looking instrument. How would I account for that? I assume I would need to use the mean looking angle somehow, but I can't see it in my head.