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 793,000 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 • 793,000+ 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 Recovery status, dates, notes, photos, settings and downloaded datasheets are stored in the app's local storage. The bundled survey-mark catalog and saved records can be used offline. You can choose to export a backup, save a photo or share a recovery card. The destination you select then receives that content and handles it under its own terms.

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

Purchases and access Markline offers three days of full access, followed by an optional one-time unlock for continued access. Starting the local access period does not create a subscription or automatic charge. Apple App Store processes payments, refunds and restoration. The app reads product prices and transaction or ownership information needed to manage access, including automatic ownership checks. Rizk Corsight does not receive your payment-card details.