The Associated Press examined the footage to verify its authenticity, cross-referencing images from the scene, aerial shots, the location of a car behind the alleged attacker and the appearance of a body and a car in the background.

NPR: UK Soldier Slaying Suspects Had Been Investigated

By cross-referencing the satellite data with a ground-based transmitter of precisely known location, the accuracy can be boosted tenfold or more.

ECONOMIST: Global positioning: Accuracy is addictive | The