Authored by Board member Tim Fassbender, PLS, CWRE
Over the course of my career, I have had the privilege of working with exceptional land surveyors and geographical information systems (GIS) mapping professionals. While often confused as interchangeable, land surveying and GIS mapping are two different professions that deliver their own unique products to their clientele. While there are similarities between the two, it is important to understand the difference between them and identify the limitations that exist for those practicing GIS mapping without a Professional Land Surveyor’s (PLS) license in Oregon.
In Oregon, you must have a license to perform professional land surveying work outlined in Oregon Revised Statute (ORS) 672.002(5). In order to receive a license, you must meet certain education and experience requirements, and have passed two national surveying exams along with one Oregon specific land surveying exam. The practice of professional land surveying is highly regulated and subject to many laws and rules found in ORS Chapter 672, ORS Chapter 209, ORS Chapter 92, and Oregon Administrative Rule (OAR) Chapter 820. GIS mapping is not a regulated practice in Oregon and does not require a professional license. These two professions have similar subject matter but vastly different requirements in order to practice them.
GIS mapping work is important and adds significant value for its intended purpose. GIS mapping is built on locations provided by the science of surveying and geodetic measurement. The GIS parcel map is built by compiling surveying information from varying sources. It generally provides a practical understanding of where locations and boundaries are but is often compiled from data produced in multiple eras. Some data is compiled from the original surveys (in Oregon, that begins in the 1860’s) and is likely not as accurate as today’s technology. These differences may not be apparent to the general public, and therefore, the public could see GIS maps as authority for setting property lines or boundaries.
Professional land surveying, on the other hand, requires the understanding and realization that there are pitfalls of compiling different accuracies of data to make one map.
Some land surveyors have reservations regarding GIS mapping and the impact it has on the public’s perception. For example, assumptions made by users can lead to inappropriate application of the GIS mapping data. Consider parcel lines on a map. When someone sees an aerial image of their home depicted with a box around it, they assume that means something authoritative. If the box is labeled “property line”, the layperson often interprets it as definitive. I have worked with landowners, and they truly believe a GIS map is the guaranteed property line location. Many of the GIS maps do contain disclaimers explicitly stating that the maps are not to be used for property line location, however it still leaves much of the data to be interpreted by the landowner. It is the responsibility of a professional land surveyor to determine precisely where that line is. Does this mean that GIS products and services shouldn’t make parcel data visible? No, it doesn’t. The issue is to right this misconception and explain the difference between a survey and a GIS map.
Both land surveyors and GIS mappers are concerned with the precision of location as it is suited for the application of data. While land surveyors focus on accuracy, GIS mapping focuses on precision. Land surveyors are trained how to interpret property deeds, including how to use the qualifying calls within the deeds, determining when bearings and distances should not be held and how to resolve conflict between deed elements. Because the GIS mapping professional is mapping out the parcels dimensions to create their parcel map, they are not required to go into this detail.
Here is another example of the difference between professional land surveying and GIS mapping. A common term, that the GIS community uses when fitting parcel lines together, is “rubber sheeting”. Meaning, they stretch and pull the line work until parcels line come together. This practice can result in situations such as a parcel line which is 100 feet in the deed becoming 103 feet in length in GIS mapping. It produces a precise but inaccurate map. Not all GIS maps are this way but knowing the limitation of the mapping warns people that the map is a great inventory of where your parcel is next to the neighbors, but it does not show the true location of the property lines.
The bottom line is that data should be well documented and used for the purpose that it is intended. Land surveying and GIS mapping are two different professions that deliver their own unique product to their clientele. PLS and GIS professionals often use GIS maps as a tool to know who may own properties in the area and what certain improvements are in the area. However, only the licensed land surveyor can determine the true boundary location and its relationship with other features.