In the last ten years we have seen dramatic advances in the clarity and availability of satellite imagery. Microsoft and Google are examples of companies now offering satellite imagery, also known as remote sensing imagery, to the public. While these images are fascinating and, in many cases, potentially useful, some people wonder if these advances spell the end of traditional aerial photography. The resounding answer is “No, aerial photography is alive and well.”

One of the reasons aerial photography remains a valuable tool is because of its superior resolution. Particularly with the advent of commercial digital equipment, an aerial platform provides very high resolution imagery, while satellite resolution remains limited by both technology and federal law. In 1999, commercial satellites could capture a resolution of one meter in black and white and somewhat less detail in color. That is, the smallest detail that could be captured and clearly outlined was at least one meter in size. There’s a popular rumor that military satellites can read a car’s license plate from space, and it’s probably an exaggeration, but it doesn’t matter if it’s true. You, as a private citizen, cannot buy or use those images anyway. Current law limits the resolution of commercially available satellite images to 0.5 meters. That means the smallest detail that can be clearly outlined is at least 0.5 meters or 19.5 inches wide. An aerial photograph at the highest digital resolution taken from 1,000 feet above the ground has about five times better resolution than the best commercially available satellite images.

Another difference between aerial photographic images and satellite images is the timing and availability of the images. Commercial satellites orbit the earth from about 400 miles above mean sea level. They orbit in a pattern and at a speed that allows them to pass over the same point on Earth about once every three days. This is fine for surveying and mapping. It generally does not allow capturing events. Generally speaking, the earth is cloudy over about 60 percent of its surface at any given time. The three-day cycle for a satellite to fly over a point can mean that it can take anywhere from a few to several dozen cycles before a clear image is available. Air flight is also subject to weather, but planes can fly below cloud cover and are available for a photo shoot anytime between sunrise and sunset. A limitation in aerial photography due to weather is usually a matter of a few days, not usually weeks or months.

One of the advantages aerial photography has over satellite imagery is the creative aspect of composition. Satellite images are usually taken from directly above. Satellite images can be taken from an oblique angle, but this introduces additional distance from the target and requires repositioning the angle of the satellite camera. Aerial photos, on the other hand, are usually taken from an oblique angle. This allows shooting from all sides and at different heights, introducing varied composition and improved usability. There is also the factor of light in the composition of the photograph. A satellite uses whatever light is available at the time it passes over its target. In an aerial photography session, the photographer chooses the light that best suits the composition of the target images. The amount of sunlight, the angle of the light, the shadows the light casts, and the time of day all contribute to a photograph that is useful for conveying information and aesthetically pleasing.

Satellite imagery will undoubtedly evolve in its ability to document, map, and study in a variety of light spectra. It is an increasingly fascinating mode of imagery. However, aerial photography remains a superior mode of capturing images from the air where direction, angle, composition and timeliness of availability are key requirements to capture the target image.