Discover the hidden survey markers all around you.
Set into sidewalks, bridges, mountaintops, and buildings across every state, hundreds of thousands of geodetic survey markers are waiting to be found. NGS Benchmark Hunter shows you exactly where they are.
Browse benchmarks near your location or search anywhere in the country. Switch to satellite view to spot markers in the field.
Tap any marker to read the full NGS datasheet, including directions to the mark, recovery history, and condition reports.
Found one? Record it with notes and photos. Track your collection and see your finds highlighted on the map.
Color-coded markers tell you what to expect. Green for easy finds, orange for moderate, red for a challenge.
Tap the location to open directions in Apple Maps or Google Maps. Navigate right to the benchmark.
Data sourced from the National Geodetic Survey. Every benchmark in the NGS database, updated monthly.
A benchmark is a geodetic survey marker placed by the National Geodetic Survey (NGS), a branch of NOAA. These small brass or aluminum disks are set into stable structures — bedrock, bridge abutments, building foundations — and serve as precise reference points for surveying, mapping, and engineering.
The first markers were placed in the early 1800s. Today, the NGS database contains nearly 800,000 entries spanning every U.S. state and territory. Some are on remote mountain summits. Others are embedded in the sidewalk outside your local post office.
Finding them is part scavenger hunt, part history lesson, and part outdoor adventure. Learn more on Wikipedia.