How to Read a Plat of Survey

A plat of survey is the sealed drawing a licensed surveyor makes of your parcel. Read it by starting at the boundary lines, then the bearings and distances that describe each line, then the monument symbols at the corners, and finally the easements and setback lines drawn inside. Every number and symbol is there for a reason, and the surveyor's seal is what makes it official. If you do not have one yet, start with what a plat of survey costs and how to get one, since a copy may already exist for your property.

Start with the boundary and the corners

The heavy solid lines forming the outer shape are your boundary lines. Where two lines meet is a corner, and at each corner you will see a small symbol: an open circle, a filled dot, or a square. The legend on the drawing tells you which is which, but the common ones are "iron rod found" (a monument that was already there) and "iron rod set" (one the surveyor placed). If you want to locate those markers on the ground later, our guide on how to find property pins walks through it.

Corners are the anchor of the whole document. Everything else on the plat, every distance and angle, is measured relative to those corners. When a surveyor "monuments" a corner, they are physically marking the legal endpoint of a boundary line so it can be found again.

Read the bearings and distances

Along each boundary line you will see a pair like N 42°17'06" E followed by a distance such as 214.90'. The first part is the bearing, the compass direction of the line; the second is the length of the line in feet and hundredths. The bearing reads as an angle measured from due north or due south, toward east or west. So N 42°17'06" E means: starting from north, rotate 42 degrees, 17 minutes and 6 seconds toward the east.

You do not need to compute anything. The point is that each line has an exact direction and an exact length, and together they trace the full outline of your parcel. If you add up the geometry, it closes back to the starting corner, which is part of how a surveyor checks the work. Curved lines (along a cul-de-sac, say) show a radius, arc length, and central angle instead of a straight bearing.

Find the easements and rights-of-way

Dashed or dotted lines inside the boundary usually mark easements: strips where someone else has a legal right to use part of your land. A utility easement lets the power or water company run and access lines; a drainage easement keeps a channel clear; an access easement lets a neighbor cross to reach their parcel. The plat labels each one, often with a width ("10' utility easement") and a reference to the document that created it.

Easements matter because you generally cannot build a permanent structure on top of one. A shed or pool placed in a utility easement can be forced out at your expense. Read them before you plan any construction, and if a labeled easement is unclear, ask the surveyor what it restricts.

Read the setback lines

Some plats also show building setback lines: dashed lines set in from the boundary that mark how close to the line your jurisdiction lets you build. Setbacks come from local zoning, not from the survey itself, so not every plat shows them. When they do appear, the buildable area is the space inside all of the setback lines, and that is where a new structure has to sit.

The title block, the seal and the legend

The date matters more than people expect. A plat is a snapshot of the parcel on the day it was surveyed. If a fence, addition or pool went in afterward, the plat will not show it, which is exactly why title companies pair an older plat with a sworn affidavit that nothing has changed. In Illinois, where a plat of survey is expected at nearly every closing, buyers see this document routinely.

How to spot an encroachment on your plat

Compare what the plat draws against what is on the ground. If the plat shows a fence, a driveway, or a neighbor's shed crossing your boundary line, or your structure crossing theirs, that is an encroachment, and the surveyor will usually call it out with a note and a dimension ("fence 0.8' over line"). Encroachments are the single most valuable thing a survey surfaces before you buy or build. If you find one, do not guess about your rights; a boundary line is a legal question, and it can help to see how courts have handled similar boundary disputes before you decide how to respond.

Frequently asked questions

What do the numbers on a plat of survey mean?

Each boundary line carries a bearing and a distance. The bearing (like N 42°17'06" E) is the compass direction of the line; the distance (like 214.90') is its length in feet. Together they describe the exact direction and length of every boundary. Curved lines show a radius, arc length, and central angle instead.

What do the symbols on a survey mean?

Symbols at the corners show monuments: an iron rod found, an iron rod set, a concrete monument, or a nail. Dashed interior lines usually mark easements or building setback lines. The legend printed on the drawing defines every symbol and line style used on that specific plat, so read the legend first.

Is a plat of survey the same as a deed?

No. A deed is the legal document that transfers ownership and describes the property in words. A plat of survey is the surveyor's scaled drawing of that same parcel, showing the boundaries, corners, easements and improvements as measured in the field. The plat makes the deed's written description visual and verifiable.

How current does a plat of survey need to be?

There is no legal expiration, but a plat only reflects the property as of its survey date. Title companies often accept an older plat if the owner signs an affidavit that nothing has changed. Any new fence, addition or subdivision since the survey date can make it obsolete and trigger a new one.

Not sure your plat is current?

If your plat is old, missing, or does not match what is on the ground, order a fresh one from a licensed surveyor. Describe your property on the Surveyors.io homepage and compare up to three quotes from license-verified, insured local surveyors within about 24 hours. See our property line survey page for what a current boundary survey includes and the land survey cost guide for pricing.