Survey bearings are the directional labels written along each property line on a deed or plat, and they take a fixed form: a leading letter (N or S), an angle in degrees-minutes-seconds, and a trailing letter (E or W). A bearing like N 45°30’20” E means: start facing north, rotate 45 degrees, 30 minutes, and 20 seconds toward the east. That single notation, paired with a distance, defines one segment of a property boundary precisely enough that any surveyor can reproduce it decades later, provided they know the reference direction the original surveyor measured from.
The Three Parts of a Bearing
Every bearing on a deed or plat follows the same format. Once you can identify each piece, you can plot the direction of any property line.
- The leading letter (N or S) tells you which end of the north-south line the angle is measured from. N means you start facing north; S means you start facing south.
- The angle is given in degrees, minutes, and seconds. There are 60 minutes in a degree and 60 seconds in a minute, the same way a clock subdivides hours. That precision lets surveyors distinguish directions that differ by tiny fractions over long distances.
- The trailing letter (E or W) tells you which side of the north-south line the angle swings toward.
So N 72°15’40” E on a plat reads: from north, rotate 72 degrees, 15 minutes, and 40 seconds eastward. That’s your line’s direction.1Bureau of Land Management. Survey Basics Made Easy
Why Bearing Angles Never Exceed 90 Degrees
Survey bearings use the quadrant system, which splits the compass into four 90-degree sectors: northeast, southeast, southwest, and northwest. Every bearing starts from the north-south line (the meridian) and swings toward east or west, so no angle ever exceeds 90 degrees.1Bureau of Land Management. Survey Basics Made Easy A line pointing due east sits exactly 90 degrees from north, written N 90°00’00” E. A line running due south has no east-west component and reads S 00°00’00” E or W.
This is different from the azimuth system, which uses a single number from 0 to 360 degrees measured clockwise from north. A southwest line that reads S 45°00’00” W in bearing notation would be 225° as an azimuth. Modern GPS and engineering software often uses azimuths internally, but deeds and recorded plats in the United States almost always use quadrant bearings.
The Basis of Bearing: What Anchors the Numbers
A bearing on its own is just a number. The basis of bearing is what connects that number to an actual direction on the ground. It identifies the specific reference line and definition of “north” that every angle on the survey was measured from. Without it, the entire plat floats, technically precise but anchored to nothing.
Surveyors pick from several reference orientations:
- True north (geodetic north) points toward the earth’s geographic axis. This is the most stable reference because it doesn’t change over time, but determining it requires astronomical observations or high-precision GPS work.
- Grid north aligns with the coordinate grid of a map projection system, such as a State Plane Coordinate System zone. Grid north and true north differ slightly depending on your location within the projection zone.
- Magnetic north is the direction a compass needle points. It shifts over time as the earth’s magnetic field changes, which creates real problems for anyone retracing an old survey.
- Assumed north is based on an existing property line, a road centerline, or a monument found on the ground. The surveyor picks a convenient reference and declares it the baseline. This works as long as the assumption is documented.
Professional surveying standards require the basis of bearing to appear on the finished survey document. The ALTA/NSPS Land Title Survey standards, which govern most commercial real estate surveys, specifically require the plat to show the basis of bearings and note any difference from the basis used in the recorded description.2National Society of Professional Surveyors. Minimum Standard Detail Requirements for ALTA/NSPS Land Title Surveys Most state licensing laws impose a similar requirement for all recorded surveys. Look for this information in the legend or notes section of a plat.
Why Old Survey Bearings May No Longer Match the Ground
Magnetic north is not fixed. It drifts over time as conditions inside the earth change, and the rate of drift varies by location. In parts of the eastern United States, magnetic declination has shifted several degrees over the past century, enough to move a property corner many feet off its true position over a long boundary line.
This creates a practical problem when retracing old surveys. If the original surveyor used a magnetic compass in, say, 1920, those bearings reflected the magnetic declination at that time and place. A modern surveyor using the same magnetic bearings today would lay out different lines, because the compass now points in a slightly different direction. NOAA maintains a magnetic declination calculator that lets you look up the estimated declination for any location and date back to 1900.3NOAA National Centers for Environmental Information. Magnetic Declination (Variation)
The first question a surveyor asks when retracing old bearings is whether the original survey used a magnetic compass or astronomical observations. If the basis of bearing was true north or grid north, the bearings don’t need a declination correction. If the basis was magnetic north (common in surveys before the mid-twentieth century), the surveyor must calculate how much the magnetic field has shifted and apply the correction before any field work begins. That is why the basis of bearing disclosure on a plat matters so much.
When Bearings Conflict With What’s on the Ground
Over time, discrepancies appear between what a deed says and what a surveyor finds in the field. The bearing might point to one location, but a stone monument or iron pin sits several feet away. Courts and surveyors resolve these conflicts using a ranking known as the priority of calls, generally running from most authoritative to least as follows:4Bureau of Land Management. The Basics of Boundary Law Study Guide
- Natural monuments such as rivers, ridgelines, and lakeshores.
- Artificial monuments such as iron pins, concrete markers, surveyor’s marks, fences, and structures placed to mark a corner.
- Distances stated in the deed.
- Bearings stated in the deed.
- Area described in the deed (acreage or square footage).
The core principle is that monuments found on the ground control over written measurements. A bearing is, in effect, a set of instructions for finding a corner, but if the corner itself is physically marked and undisturbed, the marker wins.4Bureau of Land Management. The Basics of Boundary Law Study Guide Acreage ranks last because it’s usually the least precisely determined element. The exact ranking between bearings and distances can vary by jurisdiction. In regions where historical surveys used precise chains for distance but crude compasses for direction, courts give distance more weight.
None of this is mechanical. If following the hierarchy produces a result clearly contrary to what the deed intended, the overall intent of the conveyance controls. A surveyor retracing old boundaries is doing detective work as much as math.
What This Means Before You Buy or Build
A bearing that’s off by a small amount can shift a property corner several feet over a long line, and a shifted corner can put a fence, driveway, or building foundation on the wrong side of the boundary. When that happens, the property owner typically faces one of three outcomes: removing the encroaching structure, paying the neighbor for the encroachment, or negotiating an easement or lot-line adjustment. None are cheap, and the further along a project is when the error surfaces, the worse the damage gets.
Standard title insurance policies generally do not cover boundary defects. The owner’s policy most buyers receive at closing typically excludes disputes over where the boundary actually falls. An ALTA lender’s policy provides broader protection, but it insures the lender’s interest, not the buyer’s. The most reliable protection is an independent boundary survey before closing, not after construction is underway.
If a seller provides an old survey, check the basis of bearing and the survey date. A decades-old survey based on magnetic north may no longer match current conditions, and boundary markers can shift or disappear over time. A current survey costs far less than litigating a boundary dispute or demolishing a structure that crossed the line.