Well not exactly the same. While you may be able to determine some basic relative positioning information just from looking at the picture, it's not the same a

Well not exactly the same. While you may be able to determine some basic relative positioning information just from looking at the picture, it's not the same as having the actual GPS coordinates. While you could do some perspective math plus relative positioning to known other locations to figure a rough estimate of an object it would require a fairly expert knowledge to get to the coordinates for your mortar. With GPS it's much easier for someone with far less expertise to come up with a position. Point taken that there is important information you could get from a picture alone. There's lots of other information they posses that GPS doesn't, and vice versa.