Systematic observation of places and people by visual, aural, electronic, photographic or other means.
Continuous monitoring of disease occurrence for example.
Close observation of an individual or group; person or persons under suspicion.
In criminal law, an investigation process by which police gather evidence about crimes, or suspected crime, through continued observation of persons or places.
A typically rectangular region representing the range or area currently visible (within a window, screen, etc.).
A viewing window.
To clip (an image or region) so that it fits in a viewport.