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Washington monument: taller than ever

Jan 1, 2003

Scientists perched atop the Washington Monument in Washington, D.C., in August were delighted to discover that their efforts were effective: the Monument was found to be four-tenths of an inch taller than previously thought. The obelisk was previously believed, as of a 1934 survey, to be 555 feet, 5.5 inches tall. Using the scaffolding that has enveloped the Monument for the last several years while the landmark is being refurbished, NOAA's National Geodetic Survey scientists set up three-dimensional satellite measuring equipment in accordance with the National Spatial Reference System (NSRS). Scientists determined the monument is 555 feet, 5.9 inches tall. The NSRS, maintained by the National Geodetic Survey, is the foundation for all types of surveys, and it allows government, industry, and researchers to measure the position of objects in three-dimensional space. Scientists in 1934, scrambling around a wooden platform, used spirit levels and leveling rodsand sighted measurements with their naked eyesto assist with their measurements. This past summer, seven GPS manufacturers supplied equipment and hundreds of recordings were made over a period of several days.