NOAA adjusting lat/lon reference markers

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The National Oceanic and Atmospheric Administration has begun updating its National Spatial Reference System, the network of brass, aluminum and bronze markers around the country that identify a particular latitude and longitude on the earth’s surface.

The readjustment (the first since 1986) has big ramifications for chart-making and land-surveying — anything, in fact, that uses latitude and longitude coordinates, according to David Doyle, NOAA’s chief geodetic surveyor. “[NSRS] provides the coordinate foundation in latitude, longitude and height for all the mapping, charting and surveying in this country,” says Doyle. “It is the most important part of our national infrastructure.”

For the first time, all the geodetic markers have been resurveyed with GPS. Now these new coordinates must be plugged into the NSRS. NOAA plans to unveil the system Feb. 10, 2007, the 200th birthday of the National Geodetic Survey, Doyle’s agency and the part of NOAA that maintains the NSRS.

Doyle says improvements in GPS technology are driving the quest for higher and higher levels of accuracy in the NSRS. However, mariners likely won’t see the results of a more accurate NSRS in their charts for some time. “Unfortunately, most of the charts in the United States are 25, 30, 60 years old,” Doyle says.

The new system can be used to remap shorelines without doing new surveys. Bathymetric readings, however, must be done from scratch by ships surveying the ocean bottom, and funding for NOAA’s Office of Coast Survey, which does that mapping, is often in short supply.

— Jim Flannery