Surveillance is the monitoring of the behavior, activities, or other changing information, usually of people for the purpose of influencing, managing, directing, or protecting them.
This can include observation from a distance by means of electronic equipment (such as cameras, recorder) and it can include simple, relatively no- or low-technology methods such as human intelligence agent.
The word surveillance comes from a Frenchphrase for "watching over" ("sur" means "from above" and "veiller" means "to watch"), and for us surveillance literally means eye in the sky, Notice and remember in detail.