Guides

Assessor parcel lines vs legal boundaries

County and state GIS parcel lines come from assessor tax maps, drawn to value and bill property, not to locate it. They're digitized from deeds and plats with varying care and are commonly 5 to 50 ft off, more in rural areas. The legal boundary is defined by the deed or recorded plat and the monuments on the ground, as retraced by a licensed land surveyor.

Why they're off

• Tax maps were often drafted by hand from deed descriptions and later digitized, carrying old errors forward.
• Many were fitted to older aerials or road centerlines rather than survey control.
• Deed descriptions themselves can conflict, overlap or leave gaps.
• One tax parcel can cover several legal lots, and one lot can be split across parcels.
• Easements and rights-of-way are often missing or approximate.

How to sanity-check one

• Overlay it on a current aerial. Fences, hedges and driveways that run consistently offset from the line suggest a shift.
• Compare the drawn dimensions with the recorded plat or deed.
• Look for a recorded survey of the property at the county recorder or surveyor's office.
• Check neighbors: if every parcel on the block is shifted the same way, it's the map.

What it's still useful for

Approximate lot size and shape, frontage, neighbors, and a first look at setbacks and buildable area. Anything near the line needs a survey. See base plan vs survey and free parcel data by state.

Everything here is planning-level public data. Confirm boundaries, topography, wetlands and flood status with a licensed surveyor and the right specialists before design decisions depend on them.

Related

• Public-data base plan vs a boundary survey
• How to get a parcel boundary into AutoCAD or Civil 3D
• How to make a site base plan from an address

Updated October 2026.