Remote sensing probably stated with photographs taken from balloons in the 1840s. The first automated system (not requiring human beings to be with the sensors) may have been in the 1890s in Europe when cameras programmed to take pictures at timed intervals were strapped to pigeons!
Evelyn Pruitt probably introduced the modern use of the term “remote sensing” in the mid-1950s when she worked as a geographer/oceanographer for the U.S. Office of Naval Research (ONR). Remote sensing uses instruments or sensors to capture the spectral characteristics and spatial relations of objects and materials observable at a distance, typically from above them. Using that definition, everything we observe is remotely sensed. More practically, something is sensed remotely when it is not possible or convenient to get closer.
We can categorize remote sensing for GIS many ways. Data can be taken from aircraft or satellite “platforms.” The energy that the sensor “sees” can come from the objects or areas being examined as a result of radiation emanating from them (caused by the sun or other heat or light sources) or from radiation bounced off them by an energy source associated with the sensor (e.g., radar or lidar). The images produced may be developed on film or produced by digital sensors. Satellites in geosynchronous orbits can hang in a single spot over the equator. Those in near polar orbits can see different areas of the Earth as it turns. Chapter 2 offers examples of remotely sensed ...