[0] http://www.nytimes.com/2014/05/13/science/earth/collapse-of-...
The old ones did 1Km resolution looking straight down from their polar orbits, ample resolution when you have something the size of Greenland, and I am sure the resolution has improved considerably since then. You also get several passes a day over a given location, day or night.
I dare say that this application is pretty well covered and the batteries of that drone in Antarctica (or Greenland) would have a hard job keeping up.
There is also the problem of registering whatever data you get to align with a map. Imagery from a normal plane is not that easy, given the flight characteristics of a drone I suspect that it is quite hard to get the imagery to line up even if you can fly from A to B in a straight line with GPS.
The difference is simply impossible to see. You'd have to measure decades of sea level to have a chance.