Can silent drone replace noisy police choppers?

Aerial surveillance by the police is a hot topic. News that York Region Police are using a four-engine drone equipped with battery-driven engines has added even more interest locally. Toronto Police got into quite a controversy with night-time searches for fugitives over Mt Pleasant Cemetery and elsewhere. The choppers are noisy. York police say spotting things like marijuana plants from the sky is easy. They recently used a Canadian-made drone to locate 744 marijuana plants with a street value of about $1,000 per plant in a field in the north end of Milton. A good story in the National Post makes only passing mention of whether the drones are suitable for tracking moving targets like a criminal on foot at night.  However a York officer says the drone has been used for “a variety of purposes, including monitoring crime scenes, crash investigations and search and rescue.” Sounds good.  The drone runs on batteries that provide 25 minutes of flight time, according to the manufacturer, Aeryon Labs of Waterloo. The unit returns to its starting point when it detects that the battery is low.