Remote sensing is the process of detecting and monitoring the physical characteristics of an area by measuring its reflected and emitted radiation at a distance from the targeted area. Special cameras collect remotely sensed images of the Earth, which help researchers "sense" things about the Earth. Some examples are:
Fogler Library Special Collections houses the Sewall Company Aerial Photographs Collection. It contains more than 1 million aerial photographs produced by the James W. Sewall Company beginning in 1940. The photo archive the company produced captures aerial views of nearly every part of Maine, as well as various locations in New England, Alaska, Canada, and the southern and central U.S. Many regions were photographed multiple times over the course of decades.
Fogler Library is in the process of digitizing the collection, with a focus on Maine locales. If the location you are looking for isn't digitized yet, then you should contact Special Collections.
Photographs and other images of the Earth taken from the air and from space show a great deal about the planet's landforms, vegetation, and resources. Aerial and satellite images, known as remotely sensed images, permit accurate mapping of land cover and make landscape features understandable on regional, continental, and even global scales. Transient phenomena, such as seasonal vegetation vigor and contaminant discharges, can be studied by comparing images acquired at different times. -USGS
Aerial Photography has many practical applications:
Aerial Photography and Image Interpretation for Resource Management by 
Aerial Photography and Image Interpretation by 
