A recent report by the Center for Land Use Interpretation
has shed some light on a series of two-dimensional surface paintings resembling barcodes that are scattered across the country and have puzzled Google Earth users who have spotted them.
The barcoded surfaces are aerial photo calibration targets that were created by the Air Force and NASA in the 1950s and 1960s and remain in use today, according to CLUI, a California-based research organization committed to exploring, examining, and understanding land and landscape issues.
"The targets function like an eye chart at the optometrist, where the smallest group of bars that can be resolved marks the limit of the resolution for the optical instrument that is being used," explained CLUI.
"For aerial photography, it provides a platform to test, calibrate, and focus aerial cameras traveling at different speeds and altitudes. The targets can also be used in the same way by satellites."
Most of the structures consist of a flat concrete or asphalt surface, decorated with sets of parallel and perpendicular bars – white painted rectangles, the size of which depends on their placement in the pattern – which is approximately 78 feet by 53 feet.
"The configuration is sometimes referred to as a 5:1 aspect Tri-bar Array, and . . . is still widely used to determine the resolving power of microscopes, telescopes, cameras, and scanners," reported CLUI.
Most of the targets are located within restricted areas, according to the CLUI report, such as Eglin Air Force Base in Florida; a Nevada test site; Fort Huachuca in Arizona; Wright Patterson AFB in Ohio; Travis AFB in California, and Beaufort Marine Corps Base and Shaw Air Force Base in South Carolina.
Edwards AFB in East Kern, Calif., has the largest concentration of such barcode targets with 15 in a 20-mile radius.
"There is some variation in the size and shape of the targets at Edwards, suggesting updates and modifications for specific programs," the report stated. "A number of the targets there also have aircraft hulks next to them, added to provide additional, realistic subjects for testing cameras. Some of these planes are themselves unusual and rare military jets, officially in the collection of the base museum, despite being left out on the range."
In addition to manned military aircraft, the calibration targets are also used by drone operators.
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