Remote sensing is the science of gathering information about objects from a distance without coming into physical contact with them. It thus include data gathered through photographs taken from air planes and satellites.

The technique of obtaining information from photographs is called photogrammetry.

 Sensor is another parameter to determine the types of remote sensing. According to the sensor remote sensing is of two types.

1. Photographic 2. Non-photographic.

In air photo interpretation of maps, stereoscopes and sketch masters are mostly used. Stereoscope comprises two lenses placed at the same plane termed as pocket stereoscope and mirror stereoscope.