Crash hits army’s multimillion-dollar drone program, page-9

you can loose connection with the gps for reasons other than just direct connection breakdown and at lower levels at which drones will fly there are other obstructions to that 100% connectivity .. so my point again is not single solution comms ...be it RF GPS mobile ....to be able to combine all or just some in different areas is the secret ... jaming also is another issue ... dont reply on one source of control ...
ther are other issues just oustide of teh reciver.
The whole point of Halo is this a mixture of more than one source of communciation to guarantee connection and security ... try and redcue the risk as much as possible ... but hey just my point andthey way the world appears to be heading

One of the most common causes of GPS signal loss is the obstruction of the signal by buildings, trees, hills, or other objects. To avoid this, you should find a clear and open location to fly your drone, away from any potential sources of interference.