As illustrated by this diagram, the human eye can only see a small portion of the light or electromagnetic spectrum. The colors we see are those that we commonly associate with a rainbow. As the wavelength of the electromagnetic spectrum becomes too high or too low, it becomes invisible to the human eye.
Infrared sensing provides many advantages over aerial photography. Using infrared sensing, cartographers can detect the temperatures of different objects on the ground. This can help when mapping living objects, such as plant and animal distribution. Living organisms generate heat, while dead objects generally do not. For this reason, infrared sensing is commonly used when studying crops, and the health of different habitats.