Remote sensing (RS) is the acquisition of information about an object or phenomenon without making physical contact with the object and thus in contrast to in situ observation.
Geographic information system (GIS) is a computer system designed to capture, store, manipulate, analyze, manage, and present all types of geographical data.
Global Positioning System(GPS) is a space-based satellite navigation system that provides location and time information in all weather conditions, anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. It is freely accessible to anyone with a GPS receiver.