Remote sensing is most useful in collecting information about an object or phenomenon without making contact with it. Remote sensing is the opposite to on-site observation. It is one of the techniques used when surveying an archaeological find and, is also a subset of geographical studies. Aerial sensor technologies are used to detect and classify the earth's objects. Superficial object and objects both in the oceans and the atmosphere are able to be detected and classified. The two methods of collecting data are mainly satellite photographs and aerial photographs taken by a photographer from an aeroplane or helicopter. Remote drones can also be used.