February 16, 2021 Aerial Mapping

The Liberty Gazette

February 16, 2021

Ely Air Lines

By Mike Ely and Linda Street-Ely

Mike: Our story last week was about an archeological discovery from the Iron Age, spotted in an aerial photograph. Aerial mapping has become big business. Just a week or so ago, standing outside in the front lawn, I heard an airplane and naturally, I looked up. Overhead was a Cessna Caravan making precise circles. At first, I thought the large single-engine turboprop might be a jump plane from one of Houston’s parachute centers. Then I saw a large hole in the bottom of the plane’s body. That, I knew, was for taking pictures. The airplane was mapping Liberty. 

In 2001, Google began stitching high-definition satellite photos together to create their Google Earth software program. Other companies have followed. In 2012, Google added to their universe as they began 3-D modeling of select cities.

The way it works is, a camera mounted on the airplane takes pictures of an area from four or more sides. Tilted at a 45-degree angle, it takes a series of pictures at one altitude, then the airplane climbs to a higher altitude where more images are captured. With each increase in altitude, the airplane circles at a calculated wider path, so the camera position has the same view as at the previous altitude. The photo frames are connected using algorithms and fed into Google Earth, making a three-dimensional view available from the highest altitude the aircraft took the pictures. When the screen is zoomed out to an altitude above that, the format reverts to a 2-D satellite view.

Arial photography has been around since long before satellites. Airplanes make mountain-top views available everywhere, even where no mountains exist. With their lenses pointed straight down from the airplane’s belly, the early images produced were two-dimensional; flat. Over time, the airplanes flew higher, and the cameras got better. Hundreds of pictures were taken from high-flying military airplanes flying a grid-pattern over the countryside. 

In the 1930s through the 1950s, cartographers used these photos to create topographical maps and aeronautical charts. Curved and wavy lines on the maps illustrate elevation changes, but before mapmakers could draw those, they needed to see the relief—the steepness of the terrain. The cartographer would then view the pictures through a stereoscope device to see the land in three dimensions while drawing the maps. The elevations were verified by ground survey at specific points. 

The cameras aboard Air Force spy planes take high-resolution pictures so we can learn what adversaries may be planning. They say pictures taken from the cameras aboard the SR-71 and U-2 are so clear, that even taken from 70,000 feet, you can tell the time on someone’s watch.

Though major cities were the first to be mapped, the effort has expanded regionally over time. Eventually, the whole United States, and maybe someday the world, will be available for viewing on our computers in three dimensions.  Today, the world is shrinking as cameras are coupled with GPS and are mounted in airplanes flown by pilots who fly precise circles overhead. 

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