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5 Things to Understand About Parcel Boundaries

August 29, 2023  //  BY Nicole Herold

Unless you have a dispute with your neighbor about a fence or overgrown landscaping, you probably haven’t ever really thought about the boundaries of your property since you purchased it. There aren’t lines marked on the ground to show you where your property ends and your neighbor’s property begins.

Parcel boundaries are important for many reasons, not just to resolve neighborly disputes, and factor into thousands of business, legal, and government decisions every day. Here are 5 things you may or may not know about them.

What is the difference between a parcel boundary and parcel data?

A parcel is a piece of land that is defined by a parcel boundary. The parcel boundary is the perimeter that determines the actual shape of the parcel.

Parcels can be defined as a shape or as points. A boundary is considered a shape that can be translated into a polygon on a map. The shape allows for a more complete definition, no matter how many curves or angles there are. A parcel can also be designated by a point on a map that can be located using latitude and longitude. Sometimes, there is only 1 point defined per parcel. That point can be at different levels of precision, from most precise, rooftop, to less precise such as centroid (the center point of a parcel), street, or even zip code. It is important to remember that no matter how precise a latitude / longitude point is, it doesn’t tell the whole boundary story.

Why are parcel boundaries important?

There are numerous reasons why parcel boundaries are important. Here are a just a few:

  • Boundaries provide perspective, like distances to landmarks or points of interest.
  • Being able to visualize the geographic data makes it easier for the user to understand.
  • They allow for more complicated analysis to create more insight.
  • The changes to boundaries help tell time. 

How are boundaries used?

Different industries have different reasons for needing parcel boundaries.

In land records management, parcel maps are created to show exactly where each parcel boundary is located. These maps are often referred to as assessor maps and they provide a way for anyone to see where their property begins and ends. County assessors use these maps to determine land size, which affects value and tax amount. They use shape to track who owns each piece of land.

Utility companies, like gas and electric, may need to identify properties that could be affected by an outage or need to find the best area to lay new pipe, cables, or wires.

Lenders may want to see what properties in their portfolio were affected by a natural disaster, and title companies may need to calculate how far a property is from a potential hazard, like a gas station or an industrial area.

Evolution From Paper to Digital

Parcels were once drawn on large format paper maps. The Assessor would notate on each parcel the unique identifier, sometimes called an Assessor Parcel Number (APN), which is used to track the parcel for tax purposes. Today, most counties have a Geographic Information System (GIS) department that uses mapping software, instead of paper, to create and maintain parcel boundaries. Digital maps make it not only much easier and faster to manage changes, but also to make the maps available to the public online.

Coverage, Completeness, & Currency

First American Data & Analytics has nearly 2.5 million Assessor maps across more than 1,100 counties. These maps cover 70% of the U.S. population; however, we have almost 148 million parcel boundary shapes which are in nearly every county. Like with all First American Data & Analytics public record data, we tie these parcel boundaries to taxable parcels defined by the Assessor. Not all parcels are taxed, though. Some types that aren’t taxed include federal land, state parks, tribal land, protected forests, bodies of water, streets, railroads, and government buildings.

Through sales, parcels can merge, split, and be created - as in the case of new developments. Therefore, it’s important to have up-to-date parcel boundaries to track these types of changes. Today, First American Data & Analytics currently updates parcel boundaries quarterly and is working hard to implement solutions to do this more frequently. One of the challenges managing a parcel boundary database is that boundaries are not maintained by the same county department as recorded documents. Therefore, it is possible that the changes to parcels and property owners as a result of sales are not in sync with the actual parcel boundaries someone can find on the county GIS site. First American Data & Analytics corrects this issue by using Public Record Data to ensure that the correct owner name is associated with a parcel shape and points.

The First American Difference

First American Data & Analytics makes your job easier by collecting and curating parcel data differently: we focus on accuracy and completeness. We have been collecting Assessor maps and Public Record data for decades and have concentrated on parcel boundaries – specifically linking them to the correct properties – for years because we know how important they are to our customers. With parcel boundaries and public record data connected, First American Data & Analytics offers a one-stop shop for all the best spatial and tabular property data.


For additional information about our parcel data, please email datadriven@firstam.com and we’ll get you in touch right away with one of our data experts.

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