The action of interpreting and extracting information from an object or area without direct contact is known as remote sensing and is commonly associated with data acquired by satellite, but may also include airborne and ground based techniques.
The past two to three decades have seen a revolution in our ability to survey and map our global environment. Digital sensors mounted on satellites scan vast areas of the earth's surface every day and night. Constellations of satellites beam out signals, which enable us to accurately and rapidly position ourselves, and computers store and process quantities of geographical data, which previously would have been completely unmanageable.