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# What is geocaching? 

## Geocaching is an **outdoor treasure-hunting activity** that uses GPS-enabled devices. 

In geocaching, participants navigate to a specific set  of GPS coordinates and then attempt to find the "geocache," (usually a container  or marker) at that location. The survey mark shown here illustrates how some caches may be hard to spot, even if you have the coordinates!

Geocaching  is an outdoor treasure-hunting activity that uses Global Positioning System  (GPS)-enabled devices. It can also be a valuable public service.

Geocachers often look for benchmarks—a type of  survey mark—that make up  the National  Spatial Reference System (NSRS), the foundation for all  mapping and surveying activities in the United States. NOAA’s National Geodetic Survey (NGS) defines and maintains the NSRS. For more than 200 years, NGS and its  predecessor agencies have collaborated with surveyors in both the public and  private sectors to place benchmarks across the nation. More than 1.5 million of  them were placed from the 1920s to the 1980s!

A benchmark is a brass, bronze, or  aluminum disk set in bedrock or concrete. This collection of markers forms a  network that surveyors use to accurately position other geographic points of  interest. This ensures that everything “matches up” when people produce maps,  mark off property boundaries, and plan, design, and build structures, roads,  and bridges.

Since many NSRS benchmarks are nearly a  century old, NGS wants to know when geocachers find a benchmark. Many have been  disturbed and reset through the years, and as many as half of them may have  been destroyed by construction projects. A geocacher who finds a benchmark,  measures its coordinates with a handheld GPS device, and reports the find to the National Geodetic Survey is performing a valuable public service. 

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          - National  Geodetic Survey 
          -  Geocaching Project Highlights Great Lakes Maritime History (NOAA Sea Grant)
          - ** Survey Mark Hunting Exercise for Kids
          - ** GIS Day
          - ** Geography Awareness Week
          -  ** NGS  Geocaching Forum

Did you know?

You can help keep the National  Spatial Reference System up to date! If you find a survey marker during your travels, let us know about the markers' condition using our online form. 

**Last updated:**   01/20/23**Author:** NOAAHow to cite this article

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