Markline: Benchmark Hunting

Markline is the offline field companion for benchmark hunting — the hobby of finding the brass disks, rods, and survey marks documented by NOAA's National Geodetic Survey.

More than 795,000 U.S. survey marks from the National Geodetic Survey are bundled in the app, so the catalog works with no signal, no account, and no Markline server.

WHAT YOU GET • 795,000+ NGS survey marks, bundled for fully offline field reference • A distance-sorted "Nearby" list — the closest marks to you, color-coded by their last reported condition (good, poor, or not found), with a Hide-found toggle • Bundled mark details for every entry: type, setting, coordinates (DMS + decimal), elevation, datum, stability, satellite use, and recovery history • Browse by state and county, or search instantly by PID or designation • Log your recoveries — found, not found, or destroyed — with a photo, condition, and note • Track your progress: how many you've logged and found, across how many states, plus a CSV export • Open any mark in your maps app for turn-by-turn directions, or download its full NGS datasheet once and keep it offline

WHO IT'S FOR Benchmark hunters, geocachers, surveyors, hikers, and anyone curious about the geodetic control network hiding in plain sight — the survey markers on bridges, courthouses, mountaintops, and sidewalks near you.

PRIVACY Markline has no account, no ads, and no Markline analytics. Recoveries, notes, and photo references stay on your device. Optional online features use HTTPS: Apple Maps provides basemap tiles, the App Store handles purchases, and NGS datasheets are downloaded from NOAA when you open them.

DATA SOURCE Survey-mark data is from the NOAA National Geodetic Survey and is in the public domain. Official source: https://geodesy.noaa.gov/datasheets/index.shtml

Markline is a private reference app and does not represent a government entity. It is not affiliated with, endorsed by, or authorized by NOAA or the National Geodetic Survey.

Markline v1 covers the United States and its territories (all 50 states + DC + AS/GU/PR/VI).