If you fly over the United States and look down, you can see giant barcode-like symbols embossed on asphalt panels. But these symbols are not codes left behind by aliens to track Earth or long-lost remnants of an ancient civilization.
These strange symbols were used to calibrate the lenses of aerial and satellite cameras in the 20th century. Most were created in the 1950s and ’60s, as the Cold War heated up and the United States strengthened its aerial reconnaissance technology.
Looking closely at ground level, you can see that the symbols are usually painted using thick black or white paint on a smooth concrete or asphalt surface. They are typically smaller than a basketball court and often have numerous bar-shaped lines in a regular pattern that can be used by aircraft and satellites to calibrate the optical resolution of imaging equipment.
According to the U.S. Center for Land Use Interpretation (CLUI), “Targets function similar to an eye chart at the ophthalmologist; The smallest group of bars that can be resolved here indicates the resolution limit of the optical device used. For aerial photography, it provides a platform to test, calibrate and focus aerial cameras moving at different speeds and altitudes. “Targets could also be used by satellites in the same way.”
CLUI says the targets were likely used during testing of some of the most formidable aircraft developed by the United States during the Cold War, including the SR-71 Blackbird and the U-2.
Since today’s technology does not require such calibration targets, it can easily be said that these huge barcodes have become largely unnecessary. However, there are still dozens of examples scattered near most air force bases in the United States.
Similar features can be found in other parts of the world. For example, in 2011, internet sleuths were browsing through Google Maps when they noticed several strange structures in the middle of the Chinese desert. Some were square, some had large zig-zags. One of them even consisted of giant examples of characters from the Chinese alphabet printed on a hillside. While there is much debate about the nature of the structures, there is widespread agreement that it most likely has something to do with China’s reconnaissance satellites.
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