Surveying · Benchmarks · Maps · October 24, 2026

NGS Benchmark Map: Find Survey Marks and Datasheets Near You

How to use the NGS benchmark map: search a place, open a mark's datasheet, read its PID, elevation and history, and report marks you find.

An NGS benchmark map is the National Geodetic Survey's online map of survey marks: the brass disks, rods and other monuments with published positions and elevations that surveyors, engineers and flood-zone work rely on. If you found a disk near your property, need the nearest benchmark for an elevation certificate, or just want to see what control exists in your county, the map and the datasheet behind each mark are where to look. This guide walks through the NGS map, other ways to search, how to read a datasheet, how to report a mark you found, and why a benchmark is not a property corner.

The short answer

• Use the NGS Map. Search an address or place, turn on the datasheets layer, click a mark, and open its datasheet from the pop-up.
• Know the PID. Each mark in the NGS database has a six-character Permanent Identifier, such as KX2493, which is the fastest way to pull up its record.
• Other searches: NGS also lets you search datasheets by county, station name, radius, rectangle, USGS quad or project, and download whole states.
• Read the datasheet, not just the map. It holds the elevation, position, a description of how to find the mark and its recovery history.
• Leave marks alone. Report what you find through the NGS mark recovery form, and do not dig up or move a disk.

What the NGS benchmark map shows

The National Geodetic Survey keeps records for more than 800,000 survey marks across the United States and its territories. Some are benchmarks, set mainly to carry a precise elevation. Others are horizontal control points with a precise latitude and longitude, and many have both. On the map each mark appears as a point; clicking it shows the basics and a link to the full datasheet.

The current NGS Map is a web application built on ArcGIS. Besides the survey mark datasheets layer, it can show NOAA CORS reference stations and shared OPUS solutions. It also has a search box, a measuring tool, a choice of basemaps and an attribute table you can filter by the visible map area and export to a spreadsheet file. If you are new to the idea of benchmarks, our guide to what a benchmark is in surveying covers the basics first.

How to find benchmarks near you, step by step

1. Open the NGS Map from the survey marks and datasheets section of the NGS website.
2. Search a location. Type an address, town or landmark, or a PID or station name if you already have one. Zoom in until individual points appear.
3. Make sure the datasheets layer is on in the layer list. Turn off the other layers if the map is crowded.
4. Click a point. The pop-up shows the mark's attributes, including its PID and designation, with a link to open the datasheet.
5. List everything in view. Open the attribute table and filter by map extent to get a table of every mark on screen, which you can sort or export.
6. Save the PIDs of the marks you care about so you can return straight to them later.

Other ways to search NGS survey marks

The map is the easiest route for most people, but NGS also offers form-based searches that return datasheets or GIS shapefiles:

For people comfortable with code, NGS also publishes a Data Explorer web service that returns basic mark data for a PID, a bounding box or a radius around a point, capped at 500 results per request. The text datasheet is still the full record.

How to read an NGS datasheet

A datasheet looks dense, but most readers only need a handful of lines:

• PID and designation. The ID and the station name, which should match what is stamped on the disk.
• Horizontal position. Latitude and longitude on a stated datum, usually a NAD 83 realization, along with how the position was determined.
• Height. The orthometric height (elevation) and its vertical datum, commonly NAVD 88, plus whether the value was adjusted by precise leveling or estimated in some other way. Our explainer on geodetic datums shows why the datum name matters.
• Mark description. The type of monument and its setting, such as a disk in a concrete post or a rod driven into the ground.
• Directions to reach it. Distances from roads, curbs, poles and trees. Expect these to be dated; landmarks change.
• Recovery history. Notes from people who looked for the mark over the years, including whether they found it in good condition, poor condition or not at all.

NGS also offers a newer Passive Mark Page that shows the same information in a more modern layout, with some details that are not on the classic text sheet.

Finding the mark in the field

Map coordinates get you close, but small disks hide under grass, leaves and gravel. Read the description first, then measure from the reference objects it names. Look at the top of curbs, bridge abutments, building foundations, concrete posts and culvert headwalls. A metal detector helps with buried disks and rods. Do not dig on private land without permission, and stay out of traffic.

Keep in mind that the database only covers marks NGS has published. State transportation departments, counties, cities and private surveyors set many more, and some of those are only in local records. Your county surveyor or GIS office is the place to ask about them.

Reporting a mark you found

NGS asks the public to send in what they find, because a mark is only useful if people know its current condition. The online Mark Recovery Form starts with the PID, which fills in the existing description. Individuals can use the agency code M with the agency name INDIV. You then choose a condition:

• Good: no sign of tampering or movement.
• Poor: damaged or moved enough to hurt its accuracy.
• Not found: you searched and could not locate it.
• Destroyed: only when there is clear, first-hand proof, such as a photo of the disk broken off its base. Without that, NGS wants the mark reported as not found.

Clear photos help: a close-up of the stamping, a wider shot of the setting, and one that shows nearby landmarks.

Benchmarks are not property corners

This is the most common mix-up. NGS marks are geodetic control points. They tie surveys and maps to a national framework, but they do not mark where your lot ends. A property corner is usually an iron pin, pipe or monument set by a land surveyor at the boundary; see iron pin vs iron pipe survey markers. In rural public-land states, section and quarter corners from the original government survey are different again, often with witness corners or bearing trees nearby. A benchmark sitting in your front yard does not mean the line runs through it.

Where benchmarks do touch property work is elevation. A surveyor preparing an elevation certificate for flood insurance may tie the building's floor height to a nearby benchmark or to GPS methods referenced to the same datum. For the boundary itself, start with the county parcel map and the recorded plat; our guide on finding property lines without a survey covers that side.

Leave the mark where it is

Many disks are stamped with a warning against disturbing them, and federal law (18 U.S.C. § 1858) makes it an offense to willfully remove or destroy a government survey bench mark or monument; many states have their own rules too. If construction on your land threatens a mark, contact the agency named on the disk, an NGS regional geodetic advisor or the county surveyor before work starts, since some marks can be reset and their values carried over.

This page is general background, not legal or surveying advice.

NGS benchmark map FAQ

The bottom line

The NGS benchmark map is the quickest way to see published survey marks near a property. Search a location, open the datasheet for each mark, and note its PID, elevation, datum and recovery history before you go looking. Report what you find through the mark recovery form, leave disks in place, and remember that a benchmark tells you height and position, not where the property line runs.

Related guides

• What is a benchmark in surveying?
• What is a geodetic datum?
• What is a section corner?
• How to read township and range
• What is a plat map?