The Transcontinental Traverse, a survey that crisscrossed the entire contiguous United States along three east-west and five north-south corridors, was the most accurate large-area survey ever done prior to Global Positioning System surveys. This nationwide survey increased the accuracy of the existing U.S. survey network. It was also fundamental to the sophisticated mathematical readjustment of the nation's survey network known as the North American Datum of 1983.

http://celebrating200years.noaa.gov/magazine/tct/welcome.html