Since photography began, air photos have been used to provide a permanent aerial perspective of the landscape. Until the end of the 20th century, air photos were also the source used in the creation of topographic maps. Air photos are still being used today for topographic mapping (photogrammetry), although now the photos are digital and the process uses computers (softcopy photogrammetry) rather than analogue photogrammetric machines.

• The National Air Photo Library's introduction to air photos.
• How to calculate the scale of an aerial photograph.
• A clear explanation of the geometry of aerial photographs and the effects of perspective, distortion, relief displacement, and more.
• A comparison of digital versus film photography. How modern digital video cameras work.
• A blog tracking the sales of the Vexcel [PDF] camera.
• A history of photogrammetry.
• A paper that describes the process of making orthophotos.
• How thermal sensors work (thermography).
• A brief overview of additive (RGB) and subtractive (CMYK) colours
• Your text mentions the use of GPS and IMU's and how they help in planning / taking aerial photos

Text: Chapter 4.3 Cameras, 4.5 Stereoscopy, and 9 Aerial photography

A definition of metric: met·ric2 (mtrk) ETYMOLOGY: Greek, (the art) of meter, feminine of metrikos, relating to measurement.
n.
A standard of measurement.
Mathematics. A geometric function that describes the distances between pairs of points in a space.