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Posted on March 26th, 2012

Cache of the Month – Benchmarks

About this time last year, surveyors geared up for the first-ever simultaneous nationwide GPS survey. Hundreds of surveyors participated in the event, collecting GPS data using various different methods at exactly 1 PM Eastern Time on March 19, 2011.

This event kicked off the first Surveying USA Day that is meant to give homage to the work of surveyors and their crucial role in (literally) building the United States. A number of people used this day as an education tool, including the Boy Scouts of Denver. Boy Scouts from the Denver metro area were invited to help record benchmark AE5353 near the Colorado Department of Transportation and they received a hands-on lesson on how to operate hand-held GPS units and surveying equipment. This event was also a good opportunity to educate the general public about surveying and benchmarks like the one recorded in Denver.

Above is an image of the Colorado Department of Transportation where benchmark AE5353 is located.

There is a geocaching series called the Lost Art of Benchmarking that places micro caches near benchmarks so geocachers can find both the cache and the benchmark. There is also a series on cataloging just the benchmarks themselves. In case you’re confused as to what exactly a benchmark is, here is a little wiki rundown. Benchmarks are specific locations that have a known position which is highly accurate. You will often see them as small metal plates on the ground in public or private areas. They are used by surveyors, cartographers, builders, planners and so on as accurate reference points. At this time there are about 736,425 benchmarks in the United States’ National Geodetic Survey (NGS) database.

For a more detailed description of benchmarks and the different types that can be found, click here. To read more about the history of the NGS, you can read the companion article found here.

Katie Nelson

Geospatial Ninja

(303) 718-7163

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