Finding and Using Parcel Data in California
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Whether you’re looking at housing patterns in cities, conducting a needs assessment, or analyzing lands for potential conservation value, you have most likely used, or wanted to use, parcel data for a particular place or region. Parcel data can help us in a variety of ways, however it is some of the most challenging data to acquire, manipulate and visualize. This Tech Note will provide an overview of what parcel data is, how it can be acquired, and some general tips for navigating the various difficulties that come with utilizing it. We constantly receive great questions about this type of data and this Tech Note will try to answer some of the most common ones we come across.
What is Parcel Data?
Each county in the United States divides its land into what are known as parcels. Parcels may refer to lots, blocks or any other form of land that is subdivided into units. Counties keep track of them for a number of reasons, but most commonly they are used to organize property taxing, land use and zoning decisions. Having an up-to-date record of all parcels is incredibly important to the legal, financial and real estate systems of a given place.
Parcel data generally refers to the geographically accurate information of the parcel itself, which may include property boundaries, building characteristics, lot sizes, property owners, addresses, FIPs codes, APNs and much more. Parcels such as homes and businesses are considered private, whereas others such as parks and government-owned properties are public.
Parcel data can be easily brought into Geographic Information Systems (GIS), where the parcel information is contained in attribute tables. Visualizing parcel data in a GIS is a great way to work with and manipulate the information because the data is inherently spatial. Additionally, parcel data can be formatted as spreadsheets or data tables, which do not necessarily require GIS Software.
Parcel Data Basics
Parcel data is organized on a county-by-county basis. Typically, when you start working with a parcel dataset, you will need to look for data provided by an individual county. Each county in the US has a unique Federal Information Processing System (FIPS) code. Knowing a county’s FIPS code can be very helpful when searching for localized parcel data.
San Francisco County’s FIPS Code: 06075
Los Angeles County’s FIPS Code: 06037
Mendocino County’s FIPS Code: 06045
Each parcel has its own ID as well, known as an Assessor's Parcel Numbers (APN). APNs are a series of 14 digits used to identify a property or parcel and assigned by county tax assessors. APNs may also be known as Assessor’s Identification Numbers (AINs), Property Identification Numbers (PINs), Property Identifications (PIDs).
Although parcel maps are mostly in digital form, they used to be printed in map books, which explains the format APNs are in. If the APN you were looking at was:
→ 006 refers to the map book, the largest geographic unit within a county’s parcel identification system
→ 015 refers to a specific map page within the map book
→ 3 refers to a city block number on that particular page (if there is no city block, that digit will be zero)
→ 011 refers to the specific parcel on the block, or page if there’s only one block
→ 0000 refers to the type of ownership the parcel has. Parcel’s with absolute ownership will have four zeros, just like the example. If you see numbers other than zeroes, that likely means the parcels have been divided for assessment purposes, which could include condominiums and tax segregations
Counties and cities host APN datasets on their web data portals. Depending on the city or county, you may be able to download or search for APNs within these portals. For example, if you wanted to search for APNs in Sonoma County, you could visit their Zoning and Land Use data page. You have the option to search by address or APN, or move around the map. Some county parcel datasets may also have APNs in their data tables.
Frequently Asked Questions
Where can I find Parcel Data?
Free parcel data
Most counties host parcel data for free on their own geodata hubs. However, that data is not always available to be downloaded and you may only be able to simply view it. There is no standardized place to view and download all free parcel data across the US, so visiting a specific county’s geodata hub is the best place to start. For example, if you were only interested in accessing parcel data for San Francisco, Contra Costa and Alameda counties, you might visit:
The vast majority of free parcel data you will find online does include APNs and other standard fields, but the most detailed and clean parcel datasets are usually those distributed by private companies. Because of the steep cost of parcel data owned by private businesses (see Paid-for Parcel Data), searching to see what data is available for free online is a great first step.
“Free” Parcel Data
ESRI’s ArcGIS Online is another resource for accessing parcel data. Many counties and municipalities host their parcel data on ArcGIS Online, but you will need an ESRI license in order to download and manipulate the actual data. If your university, organization or employer has ESRI licenses available, it is a great idea to get one in order to take advantage of the parcel data ArcGIS Online has to offer. Depending on the owner of the data, there may be some restrictions for what you can do with it. Although, most of the time you can bring that data into ArcGIS Pro and start working with it there.
Parcel data for the United States on ESRI’s Living Atlas is very limited. CoreLogic does host a basemap layer denoting the parcel boundaries for the entire U.S., but accessing the information within each parcel requires purchasing a license from CoreLogic’s website. Individual counties may host their own parcel data on the Living Atlas or elsewhere on ArcGIS online.
Paid-for Parcel Data
There are a variety of companies that allow you to purchase parcel datasets for nearly every county in the US. There are several advantages to purchasing parcel data from a vendor (see next question), but it comes at a relatively steep price. You have the option to purchase a parcel dataset for one county, multiple counties, one state, multiple states, and the entire country.
Purchasing this data is not inexpensive and companies like Core Logic, Boundary Solutions and ParcelQuest typically charge thousands of dollars for wide-scale data. Sometimes research institutions have partnerships with these companies, so it’s worth finding out if parcel data may be available for you to use.
If parcel data is public domain, why would I want to purchase it from a company like Core Logic, Boundary Solutions, or ParcelQuest?
Yes, parcel data is public domain. However, purchasing data from a company like CoreLogic, Boundary Solutions or ParcelQuest may be advantageous for a few reasons.
- Public parcel data may not be made available or able to be downloaded from the counties you’re working with
- Private companies host a wide range of years you can choose from; county’s may only host data from a small subset of years, or just the most recent year
- Private companies update their datasets more frequently
- Data that is purchased will likely have more information within it and the data will probably be standardized
- Data that is purchased will likely be cleaner, meaning incorrectly formatted, duplicate, or incomplete data will be removed from the dataset
- Data that is purchased may come in multiple formats (shapefiles and data tables)
If I’m only interested in 2 or 3 counties, what is the best source?
If you are only interested in a relatively small amount of parcel data (2 or 3 counties, for example), you have a couple of options.
You can visit those counties’ geodata hubs online and see if you are able to download their parcel data. Unfortunately, not every county allows you to download the parcel data, but if you are only interested in viewing it, this is your best option. If you have an ArcGIS license, visiting ArcGIS Online is another solid resource.
If you are working with a budget and have the funds to purchase a couple counties’ parcel data, your best options are CoreLogic, Boundary Solutions or ParcelQuest.
What kind of ownership info is provided? Is it enough to contact landowners by mail or email?
Typically, Parcel data tables only have limited information available about the owners of the properties. Most parcels will have the property owner’s name or the name of the company that owns the property. The data will also most likely have the address of the owner, including the state, city and zipcode. For the most part the datasets do not include contact information for the landowners, other than an address. Land that is owned by the city, county, state or federal government will generally have less information provided.
What format does it come in? Do I need GIS software? What if I don’t want to make a map?
The vast majority of parcel data available online comes in the form of shapefiles (a vector data format used in GIS) and spreadsheets, or tables. To be able to visualize the shapefiles you will need to use a GIS platform, like ArcGIS or QGIS, either on your computer or online. If you do not need to visualize the data or make a map, you can easily bring the data tables into google sheets or excel if it is in XLSX or CSV formats.
How often does parcel data change?
Parcel data is constantly changing, but whether or not those changes are reflected in the accessible datasets is a completely different story. Updates to parcel datasets depend primarily on who is providing the data in the first place. For datasets provided by the counties themselves, there is no telling when updates may occur. Some counties may update their datasets weekly, while others may update theirs on an annual basis.
CoreLogic updates their datasets on a monthly basis. ParcelQuest updates their datasets on a daily and weekly basis, depending on the county.
Can I get parcel data from counties in California?
Each county in the state hosts geographic data online in some capacity. Your ability to find and download available parcel data depends entirely on the county, but at the very least, most counties give you the option to view individual parcels and search by APNs. Below are links to every California county’s geodata hubs or parcel viewers.
Can I get parcel data from UC ANR? How about UC Davis / Berkeley / Riverside?
UC campus libraries host a wide variety of parcel data on their own geodata repositories. While the year ranges and counties included are not necessarily uniform, visiting their geodata repos are a great way to access parcel data. Depending on your campus, you may need to be a part of the institution, or have an ESRI license, in order to access and download the data. However, this is not always the case, and it’s worth checking to see if the general public has access to it.
*UC ANR does not have county-wide parcel data available online
It is also worth mentioning that campus libraries tend to have parcel data available as well. For example, the Earth Sciences Library at UC Berkeley has computers loaded with really comprehensive parcel datasets. You can reach out to a librarian to get an idea for what’s available, either online or on physical library computers.
Sample Scenario: I’m only interested in parcels greater than 5 acres, or parcels that are classified as rangeland / cropland / forested. How would I get that?
Filtering, classifying or simply working with parcel data in any other way generally requires using GIS Software of some kind. Luckily, the GIS operations needed to wrangle parcels greater than 5 acres or classified as forests, for example, are quite simple to learn. There are plenty of resources available that can help you learn these basic functions.
Filtering Attribute Tables
Knowing how to filter attribute tables in GIS environments is a great skill to have when working with parcel data. The parcel data you’re working with will have an attribute table that stores all of the information related to each individual parcel. Filtering your data allows you to focus on a specific subset of that information. There are lots of ways you can filter your data as well, including data selections, definition queries, matching records and map ranges. For example, in the data field that has information about property sizes, you can set a parameter with a filter to temporarily remove records that are less than 5 acres large. For more information about filtering attributes in ArcGIS you can visit ESRI’s guide.
Spatial intersections can also be thought of as a form of filtering, even though they are slightly different. The Intersect tool in ArcGIS calculates the intersection of feature classes and layers and produces a new data layer with their commonalities. Spatial intersections are most commonly used with polygons that either overlap, share a common boundary, or touch at a point. The result of the Intersect tool will hold the data in common between the two features. For example, if you had a layer of land classifications (i.e. rangeland, cropland, forested) and you wanted to extract the parcels that fall within the bounds of a specific class, you could use the Intersect tool to make a new layer that displays this overlap. For more information about spatial intersections in ArcGIS you can visit ESRI’s guide on this topic.
Spatial joins are yet another tool that can come in handy when manipulating parcel data. They join attributes from one feature to another based on how they relate spatially. Typically, the intersecting features from the join layer are added to the target features to create an output with just the data you want to look at. There are a few parameters you can choose from when doing spatial joins and to learn more about how these change join operations you can visit the ESRI Guide. A spatial join could be used to join parcel data with land class or census block data, for example.
Sample Scenario: How can I get the total acreage owned by a specific person or company?
Finding out the total acreage owned by a specific person or company is a surprisingly difficult task. Oftentimes the names of owners or companies have inconsistent identifiers, are hard to parse out, or aren’t contiguous within a county or series of counties. With lots of time and patience, you may be able to find the properties a single individual or company owns by using standard GIS attribute table filtering and selections. However, combining parcels by separate owners for an entire county is much more challenging and will require a more involved GIS workflow.
At the Society for Conservation GIS Conference from 2022, Carrie Schloss of the Nature Conservancy and Jayita Bhojwani of GreenInfo Network presented on the benefits and pitfalls of parcel aggregation for conservation. In their presentation they discuss why grouping parcels by owners is such a tedious task and how they were able to solve this problem, albeit not in a super streamlined way. It is definitely worth watching if you are interested in the use of parcel data for conservation lands.
What resources are out there to help me work with parcel data?
Working with parcel data can be super intimidating. Once you have acquired the appropriate parcel dataset you will need to use a GIS Software in order to massage the data to your specific needs. There are a variety of free resources online that can help you with the basic GIS functions necessary to tackle parcel data.
We hold multiple workshops and trainings throughout the year that help with everything from ArcGIS Pro to ArcGIS Online to R. To view recordings of past trainings you can visit our YouTube channel. If you would like one-on-one assistance or advice working with parcel data, you can sign up for our office hours.
ESRI has a large number of guides, workshops and videos that can help you learn about a wide variety of their products. Lean ArcGIS is a great resource for those who want to get started working with ArcGIS Pro in particular. They do also have paid-for trainings geared toward working directly with parcel data in ArcGIS. ArcGIS Parcel Fabric is a new resource provided by ESRI aimed toward those who want to manage, share and edit parcel data in both single-user and multi-user environments. This service would be helpful for those in agencies who constantly need to update and share new parcel information.