Those party animals at the National Geodetic Survey plan to celebrate the agency’s 200th birthday with a general realignment of the National Spatial Reference System.
What is the National Spatial Reference System?
“NSRS is the most important element of our national infrastructure,” said chief geodetic surveyor David Doyle.
Doyle said he was being only slightly facetious. NSRS is a nationwide array of more than a million survey reference points that serve as the foundation for all of the mapping, charting and surveying in the country.
“Everything we do is related in some way to mapping something,” Doyle said. NSRS is used to help determine zoning law compliance, to keep track of shifting coastlines and waterways, and to help guide aircraft to safe landings at airports.
The NSRS dates back to 1816, but more precise data from today’s Global Positioning System will be used to update information for the reference points in a 20-month process scheduled to be completed by Feb. 10, 2007. NGS now is a part of the National Oceanic and Atmospheric Administration, and NSRS data is available on the Web at www.ngs.noaa.gov.
You might have seen some of the NSRS survey reference points. They are brass medallions you sometimes find embedded in sidewalks or on stone markers. Others are the top of broadcast towers and some are buried a foot or more underground in fields where they won’t interfere with a farmer’s plowing.
These are passive markers. NGS also uses a network of about 600 Continuously Operating Reference Stations that broadcast GPS data. Surveyors and mapmakers use the known starting points provided by the markers to chart the nation.
A handful of NSRS markers date back to the 1820s and 1830s, although “they’re getting scarce,” Doyle said. The positions originally were determined through astronomical observations, and in the early 19th century surveyors were able to place a marker anywhere on the Earth’s surface with an accuracy of within half a mile. This is because they were working on the assumption that the Earth was a sphere.
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