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Parcels

A parcel is a plot of land that can be bought and sold.

A cadastre is a comprehensive listing of parcels in an area. Cadastres are commonly maintained and/or communicated using GIS software.

This tutorial covers the delineation and mapping of parcels in the United States.

Parcel Characteristics

While conceptions of private property in the Americas pre-dated the Columbian encounter (Gershon 2019, Greer 2012), the contemporary division of land into rigid geometric parcels largely evolved from European practice, most notably English common law.

At the time of European colonization of the Americas, land ownership was held under a tenure relationship to the Crown and involved a continuing obligation to a superior. In the Americas, a fundamental part of the revolutionary struggle was the transformation to absolute land ownership with alienable (freely transferable) ownership rights (Ely 1992).

Title

Title is legal ownership of a property (Hendrix 2018).

A deed is a written, signed, notarized document that transfers the title of a piece of property from a grantor (seller) to a grantee (buyer) (Hendrix 2018).

The current title and boundaries of a parcel can derive from a number of original and intermediate sources, including:

• Sales
• Subdivision or consolidation of existing parcels
• Treaties, purchases, and seisures from native Americans (Clarke Historical Library 2024)
• Grants from imperial authorities (New Mexico Commission of Public Records 2005)
• Headrights granted during colonization (Grymes 2024)
• Land grants and sales from the US federal government (Gates 1968)

An abstract of title is "a record of the title history of a property or other significant asset, including transfers, liens, and legal actions that are connected to the property." These documents are essential to legally demonstrate that a purchaser has clear ownership of a property (Chen 2023).

The US Public Land Survey System

The ceding of vast land areas west of the Mississippi River to the US by the British following the Revolutionary War resulted in a demand for a reliable partitioning scheme that could organize Euro-American settlement and private ownership more effectively than the ad hoc systems that prevailed in the colonial era.

The Public Land Survey System was established by the Land Ordinance of 1785 as a standard for surveying and sectioning townships prior to land sales.

• While archaic and fraught with idiosyncrasies that reflect both the technical and political limitations of its era, the PLSS is still the basis for property records in many parts of the US.
• Similar surveying systems also persist as part of property records even in locations not covered by the PLSS.
• Therefore, the PLSS still remains significant two and a half centuries after its creation.

The PLSS is based around a set of 35 initial points across the western and southern United States:

• When surveyors initially began working in a region, they chose an initial point at an arbitrary, but memorable place.
• A line of latitude east and west of that point was surveyed to form a baseline for that region.
• A meridian north and south of the baseline was surveyed to create a principal meridian for that region.
• Surveyors surveyed further meridians at six-mile intervals east and west of the initial point to create range lines.
• Surveyors surveyed parallels at six-mile intervals north and south of the initial point to create township lines.
• Because meridians differ in distance width depending on latitude, as surveyors worked north and south on township lines, they would create correction lines as parallels every 24 miles and re-survey range lines at that latitude.

These lines define the borders of specific types of areas.

• The intersection of range lines and township lines creates a grid of six-mile by six-mile areas called townships, which should not be confused with the governmental jurisdictions also called townships in many areas of the country.
• Townships are divided into 36 one-mile-square sections.
• Sections are divided into fractional subsections (1/2, 1/4, 1/8, etc.) that define particular parcels within a section.

Legal Descriptions

Legal descriptions of property give surveying information needed to identify specific parcels for legal purposes.

Legal descriptions in areas with the PLSS often include section/township/range numbers. For example, this legal description of a parcel in Lincoln County, SD shows that it is located in the northwest quadrant of section 21 in township 98 (north) and range 49 (west).

Subdivisions

Large parcels are often subdivided into smaller parcels for development and sale. In the post-WW-II era of suburbanization across the United States, the subdivision of large farm parcels into named housing developments comprised of smaller parcels for tract homes like Levittown made the term subdivision synonymous with suburban neighborhoods.

A plat is a scaled map drawn by professional surveyors.

Subdivision plats are plats for large parcels that are subdivided by developers or cities, and legal descriptions for parcels in subdivision plats reference specific numbered lots on the plat.

Legal descriptions for parcels in subdivision plats often include the PLSS location. For example the legal description for Peoria City Hall indicates that it is in Lot 2 of the Civic Center Addition subdivision, and also includes the string NE 1/4 SEC 9-8-8E, which indicates it is located in the northeast quadrant of section 9, township 8 (north), and range 8E.

Plats of Survey

A plat of survey or boundary survey is a detailed map of a parcel or group of parcels prepared by a professional surveyor that includes legal descriptions and significant physical and legal features like easements, rights of way, fences, and public utilities.

While boundary surveys are commonly associated with real estate developments, boundary surveys can be useful to individual landowners for clarifying the legal extent of their property when planning improvements or when needing documentation for the resolution of disputes with neighbors.

Downloading PLSS Boundaries

PLSS boundaries are available from a Bureau of Land Management (BLM) feature service linked on the National Map Services website. The feature services have a limit to the number of features that can be downloaded at any one time, which limits downloads to areas like counties.

1. Add a clipping area feature class to your map.
2. Find the REST endpoint URL for the townships feature service and add that layer to your map.
3. Run the Clip tool with the townships and the clipping area to create a new feature class in the project geodatabase (County_Townships)
4. Find the REST endpoint URL for the sections feature service and add that layer to your map.
5. Run the Clip tool with the sections and the clipping area to create a new feature class in the project geodatabase (County_Sections)

Alternatively, some state agencies provide downloadable subsets of of PLSS data, such a this downloadable shapefile of PLSS section boundaries from the Illinois State Geological Survey.

Valuation

An assessor is a local government official responsible for determining and recording the value of properties for local real estate taxation purposes (Kagan 2021). County parcel data is typically maintained and distributed by county tax assessor's offices, and assessors make assessment data available to the public as public records.

Appraised value is a evaluation of a property's value at the time of appraisal (Chen 2023).

• An appraisal is made by a professional appraiser when a buyer gets a mortgage to determine how much money a buyer can borrow and under what terms.
• A lender may require a borrower to get mortgage insurance if the ratio of the loan value to appraised value (LTV) is greater than 80%.
• An appraised value may not match the sale price or market value of a property, especially when the housing market is tight.

Assessed value is the value of a parcel used for calculation of property tax.

• Assessed values are commonly listed in parcel records based on different categories like land value, building value, farm building, farm land, etc.
• Improvements are investments in structures or changes to a parcel that increase its assessed value.

The assessment ratio is the legally (usually state) defined multiplier to convert appraised values to assessed values.

• Assessment ratios range from as low as 9.5% in Wyoming and 10% in Louisiana, to as high as 100% in Massachusetts.
• Assessment ratios can vary based on the type of property (residential vs. commercial).
• Assessment ratios are related to, but different from, tax rates (see below).

Because appraised values influence the resale value of homes and can dictate whether buyers need to get mortage insurance (if the sale price is greater than 80% of appraised value), sellers may want to assure that their appraised values are close to market value. This is often especially problematic for sellers in minority neighborhoods where negative perceptions may incline appraisers to values below market value (Rothwell and Perry 2021).

On the other end of the income spectrum, landowners in wealthy neighborhoods may want to minimize their assessed values to minimize the property taxes based on those assessed values. Affluent landowners have the legal knowledge and resources to challenge and reduce assessed valuations, while poor landowners lack those capabilities and often have higher assessments relative to the market value of their properties. (NY Times 2021).

Property Tax Rates

Property tax rates are percentages of assessed value that must be paid each year.

• Property tax rates are usually published on the county's web site, sometimes in PDF files.
• Property tax rates often vary widely across counties and across localities within counties.
• Property tax rates are often the sum of a variety of different taxes including school district taxes, county taxes, city taxes, library taxes, road taxes, park district taxes, and sanitary district taxes.
• Because some elements of property tax rates are fairly small they are are often expressed in millage, which is the amount per $1,000 of assessed value or one tenth of one percent of assessed value.

Acquiring Parcel Data

Property records are public data, and assessors offices commonly make parcel information available on their websites either in searchable form or on web map apps. However, publicly available free data in geospatial formats that can be conveniently imported into GIS is somewhat more rare.

Map Apps

Many counties provide online read-only viewers for examining parcel data. These viewers provide no obvious facility for downloading parcel data, although data may be available elsewhere on the assessors's site, sometimes for a fee. ESRI map image layers are sometimes used to implement these viewers, but they are also sometimes implemented with proprietary solutions.

ArcGIS Hub

ArcGIS Hub is a CMS for geospatial data which was created by ESRI (the dominant company in enterprise GIS) and is tightly integrated with their ArcGIS Online and ArcGIS Server software.

ArcGIS Hub allows users to download data in a variety of formats, although server-side conversion to a downloadable file can take a few minutes with large data sets like parcels.

Shapefile Downloads

Some sites make their current parcel data available as downloadable zipped shapefiles.

Purchase Data

Some counties charge fees for downloadable GIS cadastral data.

Regrid

If you have the funding, Regrid is a commercial service that provides standardized parcel and zoning data for all US counties.

Mapping Parcel Data

Parcel Map

Because parcels are numerous and generally individually occupy small areas of land, web maps of parcels need to limit the number of parcels that can be displayed at one time. This is commonly done by using scale-dependent rendering that only displays parcels when closely zoomed into the city.

Group layers combine multiple related feature layers into a single bundle that can be easily added to web maps and kept together in the layers list.

Parcels can be included in a group layer that shows parcels below a specific zoom level, and then shows a less fine-grained layer when zoomed further out.

This example demonstrates the creation of a layer of parcels in Peoria County, IL, grouped with section boundaries from the Bureau of Land Management clipped to the county boundary.

1. Add and symbolize the layers.
• Add the PLSS township and section feature classes created above and use a symbology of red borders.
• Add firstdivlab labels to the sections.
• Add the layer of downloaded parcels and use a symbology of blue borders.
2. Under the map Properties, set the Coordinate Systems to WGS 1984 Web Mercator (the projection used for most web maps).
3. Under Properties, General, adjust the visible range for the features:
• Parcels: Minimum scale 1:24,000
• Sections: Maximum scale 1:24,000 and Minimum scale 1:200,000
• Townships: Maximum scale 1:24,000
4. Group the layers.
• Group the township layer.
• Drag the the parcel and section layers into the group.
• Rename the constituent layers to remove the database name.
• Rename the group layer (Parcels)
5. Share, As web layer as a Map Image with Feature layer under a meaningful name that is unique in your organization (Peoria_Parcels).
• Ignore the error 10001 about different projections and error 24035 about group layers not supported.
6. View the feature layer in an portal web map to confirm appropriate scaling and display.

Parcel Viewer

Counties commonly create parcel viewer web apps with details panes that include parcel attributes like:

• Parcel ID
• Parcel address
• Owner
• Property categor(ies) and/or description(s)
• Land area and living area
• Assessed value(s) (land, buildings, farmland, farm buildings)
• Appraised value(s)
• Legal definition

Parcel maps can be presented with detail panes using ArcGIS Experience Builder.

1. From your portal Content page, Create app and Experience Builder with a Blank fullscreen template.
2. Drag a Map onto the canvas.
• Select map and Add new data with a map of the parcel data you created above.
• Disable pop-up
• Style the map to fill the left 70% of the screen.
• Under Action, Add a trigger for Record selection changes to the Framework to Filter Data Records, with Trigger data and Action data both pointing to the parcel layer.
3. Drag a List onto the right side of the canvas.
• Under Content select the simple image and text format.
• Style the list to fill the right 30% of the screen.
• Under Content, Start, and Select data with the parcel layer and Selected features.
• Resize the top list text box to fill the screen
• Edit the text box to add formatted text.
4. Add a Header (Peoria County Parcel Viewer).
5. Test the app in Live View.
6. Rename and save the app.

Responsive Web Design

The details pane layout above is well suited to a desktop or laptop, but is too wide for tablets or mobile phones. Since almost half of internet traffic is on mobile phones

Responsive web design involves creating web pages and apps that automatically adjust for different screen sizes. Mobile first design is a related approach that involves designing for the smallest device first and progressively adding features as you move to larger screens.

Experience builder apps have the ability to create separate layouts for tablets and cellphones within the same app.

Switch to tablet mode, click the Custom button, and move the list to the bottom 50% of the screen.

Disclaimer

Because a web map is a visual representation of a cadastre that can contain imprecise or inaccurate information, you need to get confirmed acceptance of a disclaimer to avoid legal liability for decisions that users make based on the web map.

A splash screen is an image or window that pops up when a web page is loaded. While splash screens are often regarded as a poor design choice because they interfere with an efficient user experience and can repel visitors, parcel viewer websites commonly use splash screens to get acknowledgement of the legal disclaimer before the site will load.

Experience Builder supports splash screens.

1. Go to the Page panel, click the Window tab, click the Add window button, and select the Confirm template.
2. Add the disclaimer text to the text box.
3. Click the Set as Splash icon in the Page panel window entry.
4. Save, Publish, and Preview to verify the screen.

Parcel Fabric

Parcel Fabric is an integrated set of schema, tools, and workflows that organizations can use to manage parcel data in conjunction with associated data about ownership (cadastres), subsurface infrastructure, air rights, and natural resource rights.

Parcel Fabric adds significant complexity to a parcel data set that is unnecessary for assessor's office maintenance of current parcel attributes. Parcel Fabric is primarily useful for engineering and recorder's office tasks like:

1. Management of legal descriptions
2. Maintaining data at survey grade accuracy for engineering purposes
3. Managing changes over time, like subdivision and boundary adjustments

Affordability

Income

Assessed value from parcel data can be used to get a general picture of housing prices in an area. The question of affordability then relates to income and how much house you can buy for your money.

The Occupational Outlook Handbook provides estimates of employment and salaries for metropolitan statistical areas around the US.

This example shows the mean salary for surveying and mapping technicians of $56,320 in the Chicago metropolitan area.

Payment Calculation

The 28/36 rule indicates that mortgage costs should account for no more than 28% of income, and total debt payments should total no more than 36% of your pre-tax income (debt-to-income ratio). Other debt payments you need to consider:

• Student loan payments
• Auto loan payments
• Long-term credit card debt
• Payments on home improvement loans
• Mortgage payments on other properties like vacation homes

The formula for mortage payments under a fixed-rate mortgage is fairly straightforward:

Where:

• P is the principal amount (cost of home - down payment).
• I is the interest rate (0.07 was a typical value in summer 2024).
• N is the number of payments (360 monthly payments on a typical 30-year mortgage).
• M is the monthly mortgage payment.

However, there are numerous additional additional home ownership costs that need to be considered in the monthly costs of owning a home:

• Property taxes
• Home insurance
• Homeowners association (HOA) dues
• Home improvement costs needed to upgrade and maintain an older home

While you can transform the formula above and use the 28/36 rule to estimate how much house you can afford, online home affordability calculators like this one from Zillow can make the calculation simpler and more intuitive.

Schools

One major consideration for home buyers is the quality of local schools. In the United States, schools are largely funded by local property taxes, which generally gives an advantage to students who grow up in expensive neighborhoods. Local control and funding of public schools encourages parents to purchase the most expensive home they can afford so their children have the advantages of well-resourced schools as they grow.

A variety of organizations publish school and school district performance data, sometimes as web maps. While fraught with biases and generalizations, such statistics can be helpful guides when searching for a neighborhood where your children will get the best start in life.

Statistics on these web sites include the following. Because the collection methodologies vary by state and locality, interpretation of these values should be made in the context of other local institutions.

• Average SAT scores (overall average is around 1050)
• Percent of students with free or reduced price lunch (a metric of neighborhood poverty)
• High school graduation rate (2021-22 US average was 87%)
• Teacher retention (a metric of institutional stability - the 2020-2022 national rate was 84%
• Percent meeting or exceeding SAT expectations
• Student mobility (percent of students who transfer in or out during the school year - metric for neighborhood stability)
• Standardized test proficiency (ELA, math, science)

State boards of education commonly publish school and district performance information. For example, the Illinois Report Card provides information on schools in Illinois.

The Memphis Teachers Residency has published the EdGap.org web map with high school SAT performance data for a number of states.

Counties with Publicly Available Parcel Data

• Arkansas, Benton County (shapefile)
  https://gis.bentoncountyar.gov/downloads/index.html
• Colorado, Arapahoe County (download form)
  https://gis.arapahoegov.com/datadownload/
• Delaware, Kent County (Hub)
  https://gis-kentcountyde.hub.arcgis.com/pages/open-data
• Florida, Okaloosa County (shapefile)
  https://okaloosapa.com/gis-mapping/
• Georgia, Macon-Bibb County (Hub)
  https://hub.arcgis.com/datasets/7787b8ee3ebe40b99f6d4c5baf075ef3_0/explore
• Idaho, Madison County (Hub)
  https://hub.arcgis.com/datasets/72001d5ee9984277bcea99a9e0e3a055_0/explore
• Illinois, Peoria County (Hub)
  https://hub.arcgis.com/datasets/00b0e55fe72d414395418dd76691daf4_5/explore
• Illinois, DuPage County (Sites)
  https://gisdata-dupage.opendata.arcgis.com/datasets/b47d0bd9cef14b2fbeec45bc0df50935_0/explore
• Indiana, Vanderburgh County (Hub)
  https://hub.arcgis.com/datasets/eb92dc98ed854334a2ff7e8d2a708311_0/explore
• Indiana, Hamilton County (Hub)
  https://hub.arcgis.com/datasets/4ed17381d7374266ab1f37d1483c1fde_1/explore
• Iowa, Linn County (Hub, attached photos)
  https://hub.arcgis.com/datasets/7c99f1a69ce14bdbaed102439cadc70e_0/explore
• Iowa, Pottawattamie County (Hub)
  https://hub.arcgis.com/datasets/d865c806738045ccb269bf3632803b19_0/explore
• Maryland, Harford County (Hub)
  https://hub.arcgis.com/datasets/8f5f2803fffc4f6fb9397fc12beb52d8_0/explore
• Maryland, Montgomery County (File GDB)
  https://hub.arcgis.com/datasets/46adf9a319854672828ac192436d8e98/about
• Minnesota, Olmsted County (Hub)
  https://hub.arcgis.com/maps/51dd36745ef14dce8c75cf5ee1039870
• Mississippi, Harrison County (Hub)
  https://hub.arcgis.com/datasets/ddc11961da6b413397a659b1fc74cf39_0/explore
• Montana, Lewis and Clark County (Hub)
  https://hub.arcgis.com/datasets/59f1dc01232049a9b77b068cce07a488_5/explore
• Nebraska, Sarpy County (Hub)
  https://hub.arcgis.com/datasets/870d5e73fd3e43e3b8e5f9a2029b9573_5/explore
• Nebraska, Cass County (Hub)
  https://hub.arcgis.com/maps/7952a5e2b11e4e8bbeecb63f1187b739
• Nevada, Washoe County (Enterprise)
  https://explore-washoe.opendata.arcgis.com/datasets/d459154b4687475f8baefda30532f826_0/explore
• New Jersey, Somerset County (Hub)
  https://hub.arcgis.com/maps/a762d956e4c04178a8ce24bc5026f3d9
• New Jersey, Gloucester County (shapefile)
  https://hub.arcgis.com/documents/70c5b83e661f4d17b14a54642ba07439
• New York, Albany County (Hub)
  https://hub.arcgis.com/maps/f09081443be94a78b88f1a7dc239683a
• North Carolina, Orange County (Hub)
  https://hub.arcgis.com/maps/bfb50d32050e4511a0fed2c645a9d498
• North Carolina, Buncombe County (Hub)
  https://hub.arcgis.com/maps/969e8c8088a34464961d227d8b1c3f38
• North Carolina, Durham County (Hub)
  https://hub.arcgis.com/maps/3c2156afa42a4890bd31ef905d151dbb
• North Dakota, Burleigh County (Hub)
  https://hub.arcgis.com/maps/f33dd0bf759944f59b28def11d350897
• Ohio, Williams County (Hub)
  https://hub.arcgis.com/maps/45b7df6d2cf2449d894c03c59da6e23d
• Ohio, Greene County (Hub)
  https://hub.arcgis.com/maps/9a203896be6c44f083080c4bf22f9358
• Ohio, Delaware County (Hub)
  https://hub.arcgis.com/maps/cd8f9ac644ec4dc1979b254193b895a2
• Ohio, Stark County (Hub)
  https://hub.arcgis.com/maps/bbeab7fa5368494c980e80be42d230f1
• Oklahoma, Canadian County (Hub)
  https://hub.arcgis.com/datasets/7bbc6322290241a891f237dc43ed16bd/explore
• Oregon, Josephine County (shapefile)
  https://www.josephinecounty.gov/departments/geographic_information_systems_(gis)/gis_data_download.php
• Pennsylvania, Montgomery County (Hub)
  https://hub.arcgis.com/maps/228cad7975554088a350bee4caf3ca45
• Pennsylvania, Bucks County (Hub)
  https://hub.arcgis.com/maps/3a4d9c4305874312a2a74da7bd55a22d
• Pennsylvania, Chester County (Hub)
  https://hub.arcgis.com/maps/743f6f125f1e41589c0c9841d65a0ade
• Virginia, Pittsylvania County (Hub)
  https://open-data-pittsylvania.hub.arcgis.com/
• Washington, Spokane County (Sites)
  https://gisdatacatalog-spokanecounty.opendata.arcgis.com/datasets/parcels/explore
• Wisconsin, Eau Claire County (Hub)
  https://hub.arcgis.com/maps/6331d72454ab480fb363976d03e876c6
• Wisconsin, Wood County (Hub)
  https://hub.arcgis.com/maps/de2d631e58a040d1ab89587c432785cc
• Wisconsin, Racine County (Hub)
  https://hub.arcgis.com/maps/e8457d4f38c04eeb8a74fbe902ca86ff
• Wyoming, all counties (county in jurisdicti field) (zipped shapefile)
  https://wyo-prop-div.wyo.gov/tax-districts/maps-gis-data