You've been successfully unsubscribed.

The easiest way to find, save, and personalize your search for the perfect piece of land.

Thank You

Thank you for signing up for a Account!

Please check your email for instructions on how to activate your account with one click.

If you do not receive an email from us, please check your spam folder.

Buying LandOwning Land

How to Perform Overlay Analysis in GIS

November 2, 2018

Land brokers rely on many tools to help clients understand their property and these sometimes include a variety of systems provided by county governments such as robust Geographic Information System (GIS) tools like overlay analysis that can help landowners understand the property better. This blog post uses several counties in the mountains of Western North Carolina as examples, but almost every county across the nation will have some sort of similar system for the public to use.

Since each county in the region has different GIS tools, there is a bit of a learning curve to understand them all. However, Buncombe County and Henderson County tend to be the most updated and offer the most information. Madison, Yancy, Mitchell, McDowell, Rutherford, Polk, Transylvania, and Haywood Counties have GIS tools as well, but they vary greatly in available overlays, and some are infrequently updated.

Generally speaking, each of these tools allows users to find a property based on address, owner, or Property Identification Number (PIN). From there you can see the approximate (not surveyed) boundary. You can also turn on or off layers such as satellite images, topography contours, surface water, zoning, and other overlays. Many of these are useful for researching the property’s features.

GIS technologies are used in a variety of fields today, including many forms of project planning. For example, many urban planners will use GIS to analyze population growth and expansion patterns to determine suitable locations for new developments. Similarly, many transportation planners will use GIS to find viable locations for new railway lines based on factors like the flattest route, most central location, and lowest likelihood to cause environmental harm. Due to the prominence of GIS technologies in our modern world, it is prudent to have a general understanding of how they function.

What are GIS Overlays?

Essentially, GIS overlays are ways of examining and analyzing various kinds of geographic features within the GIS. These overlays help to understand which things are situated on top of other things. For example, GIS overlays would be able to show you what kinds of soil types are commonly used on farming properties in your area, or if there’s a forgotten well underneath your property. GIS overlays can also be laid over pre-existing mapping software such as Google Maps, to identify various metrics including businesses in the area, topographical trends, soil compositions, property lines, and much more.

GIS overlays can help to determine suitable locations to build a home, as they can easily be used to identify features like flood zones, proximity to amenities, topographical incline, and many more. 

Typically, GIS overlays require two inputs: the input layer, and the overlay layer. These layers could be singular points on a map, lines, or more general zones that you would like to examine.  Once your inputs have been determined, you can use GIS in a few different ways to produce various outputs:

  • Intersect– This output shows areas where your inputs overlap. This is the most common way of using overlays, as it allows you to see where two features meet, for example, you could examine a watershed area to see which areas of it have a certain kind of soil composition.
  • Union– This output shows the entirety of your inputs, rather than just the areas where they overlap.
  • Erase– This output filters out certain areas based on your inputs. For example, if your city is looking to build a new sports facility, they may use this kind of output to see if there is enough available land in a certain area for their project.

How is Overlay Analysis in GIS Used?

GIS overlays can be used for a variety of things, however, National Land Realty typically uses them to locate possible clients and buyers. If a Land Professional is helping a client sell their land, they might use GIS overlays to determine if there are other landowners nearby that may be interested in purchasing additional land. Similarly, National Land Realty Land Professionals use GIS to help them decide on the best use for a specific property by examining soil types in the area and the best uses for those soil types.

Furthermore, GIS technologies are used by National Land Realty’s Land Professionals to search for specific types of properties for their clients. For example, perhaps a client might say they’re looking for a 50-acre property that’s close to a good school district and has good soils for farming. Our Land Professionals can take those criteria, and by using GIS, filter out any other properties that don’t meet those requirements. In this way, our Land Professionals can be certain that their clients are seeing every possibly appealing property. 

National Land Realty employs a dedicated GIS team to ensure that our data is up to date and accurate in order to match each client with their perfect property. This team works tirelessly to keep our Land Professionals and Brokers updated with the latest GIS data and information.

Now that you have a general idea of what overlays are and how they can be used, we will discuss more specific applications of GIS overlays. These examples are pulled from several Northern California counties but should be relatively applicable across counties and regions.

Overlay Analysis for Flood Data

Most systems allow users to overlay Federal Emergency Management Agency (FEMA) developed flood maps. There are options to see the floodway (the area most likely to flood, development is normally prohibited), the 100-year floodplain (where a flood would be expected every 100 years on average), and the 500-year floodplain. It’s generally inadvisable to build any structures in these areas, but they could be used for agriculture and conservation.


Some counties offer slope analysis or zoning information. Buncombe County has an overlay called “County Zoning Overlay” that allows you to see what portions of the parcel are zoned as steep slopes and what portions are protected ridgelines. These areas will require additional permitting and some uses may be restricted.  Henderson County has a slope overlay that identifies where slopes are 0-16%, 16-25%, 25-60%, or over 60% based on colors. And Rutherford County allows for a slope overlay that estimates slopes in 10% increments.

Overlay Analysis for Conservation Easements

Haywood and Mitchell Counties allow for an overlay to see which lands have been placed in conservation easements. This is important since you wouldn’t want to purchase a property for its mineral rights if there’s a pre-existing easement that prevents you from harvesting those minerals.


Buncombe County also has a stability index map overlay that shows where there is a low, moderate, or high risk of hazard for landslides and other earth instability. It should go without saying, but this is important information for anyone looking to build a structure on a property, as unstable ground could be a hazard to any construction projects.

Knowing how to access these tools can help landowners and buyers understand more about what is possible on a property. They provide valuable information that can be used for planning and decision-making. Having a decent understanding of GIS technologies and overlay analysis can be helpful outside the land industry as well since so many of our modern corporations and government agencies utilize GIS on a daily basis. 

I help my clients understand land and provide them with education and knowledge to make informed decisions. I also ensure they are working with the right legal, surveying, soil, and landslide consultants, foresters, and other professionals to protect their interests and their land. If you’re looking for a professional land broker or need help understanding land issues like this, let me know! Pat Snyder,

About the Author
Pat (he/him/his) is a retired U.S. Air Force officer, active Rotarian, and manages Western NC land brokerage for National Land Realty. Clients hire him to help them navigate difficult land transactions, which he does through a consultative team approach. This includes research, analysis, and collaboration with trusted vendors and experts, all executed with skillful project management to keep transactions on schedule. Pat was ranked #9 out of over 21,132 regional REALTORs in total Land Sales for 2021 and ranked #12 in the nation for National Land Realty brokers that year. For Seller Clients: Pat invests in every client with unmatched national advertising tailored to appeal to the most likely buyers with a team of professionals who ensure properties have the best exposure. For Buyer Clients: He devotes time to educating and empowering them to make decisions based on market trends, conservation, timber, land use, legal concerns, and other factors important to land buyers. Pat is a Certified Negotiations Expert, REALTOR Land Institute Member, and on the board of directors of the Rotary Club of Asheville and EcoForesters (a non-profit focused on sustainable forestry practices and protecting the native Appalachian landscape). View Pat's Listings and Reviews on