Agree with Skycop. Vfr, I think you'll find that the police and ENG helos over London were between 1000 ft and 1500 ft agl: well above the 'legal' minimum heights iaw CAA permitted exemptions.
The value of the airborne camera is that it is truly mobile and is backed up by three sets of Mk 1 eyeballs that can assist far more effectively than a battery of fixed cameras.