Why Photography?

Aerial photography, like all remote sensing technologies, has advantages and disadvantages compared with other remote sensing tools. The advantages of using photography to assess threats over time include: a long history of repeat coverage, it is well understood, it is intuitive to the user community, it has excellent resolution, and it provides a superb stereo view.

The Forest Service has been systematically collecting aerial photography since the 1930s. Since that time, considerable effort and expense by developers have resulted in significant improvements, including faster and more resolute films and film types, faster and more resolute lenses and cameras, and more precise camera geometries and calibrations. On the users’ side, there is a long history of effective use and technique development. These developments include a thorough understanding of photo geometry, stereoscopy, photogrammetry, and interpretation. Thus, the complexities of photography are well understood in the professional community.

Although photography is complex, it is simultaneously intuitive—both to the professional community, and to the at-large community. We’ve all grown up with photographs as part of our daily lives. We may not always understand the complexities and properties of the photography we see, but we still know how to interpret photographic images. Photography’s intuitiveness promotes a greater understanding and acceptance of analytic results by the public—especially when the analysis techniques are easily understood.

Photography has excellent spatial resolution that is only now being challenged by other imaging systems. Even early aerial photography (1930s and 1940s), though not as resolute as post-WWII photography, has very good resolution. This allows easy comparison of vastly different dates of imagery.

An under-appreciated property of aerial photography is the ability to view the imagery in stereo. The stereo view drastically increases our ability to discern what we are viewing in the image and to perceive the topography and the varying heights of features on the ground. The stereo view has been the domain of the stereoscope and hardcopy photographs but is now becoming easily accessible in the digital domain—a trend that is certain to continue.