I'm developing the use of UAVs out here in Kenya for wildlife and livestock census using vertical photography. Known as Aerial Point Sampling (APS), sample photos are taken at intervals along each flight line and the total number of animals is estimated from the numbers counted on the photographs.
The geographic coordinates of each photo are trivial to capture from the GPS systems. What is more difficult is the height above ground level (height AGL) which is required to exactly scale each photo.
My UAV (based on the MAJA airframe) maintains a pre-programmed QFE height AGL, and while to some extent you can pre-programme a height AGL flight profile it is still ...