Intersect: Data Fit for Purpose
Professional Surveyor Magazine - June 2011
Janet Jackson, GISP and Randy Rambeau, Sr., PLS
GIS Janet says...
Understanding the phrase “data fit for purpose” is a giant step in the right direction—the direction of connecting GIS and surveying. It allows professionals in both GIS and surveying to perform to their best while maximizing their joint efforts for clients. So that everyone understands the meaning of this commonly heard phrase, let’s attempt to define it.
The first person I ever heard use that phase was Brent Jones, survey industry manager for Esri
. Brent explained that if the data you are collecting were to be used in a legal or authoritative function, a surveyor would need to do the data collection and documentation. A good example is a boundary survey, as the measurements need to be exact and the final document needs to be signed and professionally sealed by the surveyor. However, if an asset inventory, such as hydrants, needs to be done, it would be perfectly acceptable to have a GIS professional collect and document them.
Why the difference? Because the hydrant data will be used for purposes other than exact location. Information such as the date of last repair, make, model, etc., is just as valuable to the owner. In other words, how the data will be used is the guiding factor for who should collect the data, how that data should be collected, and to what level of accuracy it should be measured, documented, and represented.
Many more great examples of “data fit for purpose” are right there in the palm of your hand, either through your cell phone (with GPS) or Google Earth
with specialized LBS (location-based services). The exact X/Y coordinates of your local McDonald’s don’t need to be surveyed and uploaded to your handheld device for you to successfully find the closest McDonald’s. The “data fit for purpose” in this case is that you need only a reference point (dot on the map, not the exact X/Y coordinates) for that data to be used successfully. However, now that the dot is on the map, it could be up to the surveyor to make each dot more accurate over time.
With that basic understanding of “data fit for purpose,” I can see where surveyors and GIS professionals should and will be working side by side in the field to collect and document field assets. Many of our clients need the precision a surveyor offers, such as obtaining the invert of a sewer line combined with the manhole attributes collected by a GIS professional.
“Data fit for purpose” might be a new concept to some, but it’s just a new way to think about things you see every day, and how and by whom they could best be represented to others. Clifford Stoll, a U.S. astronomer and author, said, “Data is not information, information is not knowledge, knowledge is not understanding, understanding is not wisdom.” I guess Mr. Stoll understands that each phrase stands alone until the efforts—in this case, of the surveyors and GIS professionals—are combined.
Surveyor Randy says...
The phrase “data fit for purpose” may have just arrived on the scene, but the concept has been around for decades, probably centuries, in the surveyors’ world. It seems that “fit for purpose” is determined by accuracy, thereby dictating the methods and equipment used to obtain that accuracy.
In my early years of surveying, decisions were routinely made to obtain the data to the accuracy that was needed. Sometimes we paced the distance between points, sometimes we measured with a cloth or steel tape, and sometimes we measured it with an EDM.
Likewise, different methods were used for angles. Occasionally, the accuracy needed was obtained by “clapping a 90”; at other times, a pocket compass, transit, or theodolite was used. Surveyors may not have had the catchphrase, but we certainly employed the practical application of the concept.
Professional surveyors may not totally agree on the accuracy needed for a particular dataset, but we, along with GIS professionals, realize there is a range of accuracies and applications required for various survey data. Perhaps the common ground both professions need to seek is agreement on the accuracies of these datasets and the associated metadata.
Reaching that common ground can be beneficial to both professions. I recently read an article stating that it would cost $375 billion to replace the existing geospatial data in the United States, according to an estimated annual growth of $10 billion in geospatial data. This need for new and more accurate geospatial data has to provide opportunities for both professions at what could not be a better time.
Professional surveyors and GIS professionals may very well have a conduit for connectivity with “data fit for purpose” and may also understand the difference in accuracies and the limits of use due to those accuracies. My concern is the lack of understanding by the folks outside our professions. The amount of data easily available to the general public and related professions is astronomical. With the avalanche of information accessible at almost everyone’s fingertips via the internet and mobile devices, it is understandable that data “unfit for purpose”
could be used in an inappropriate manner. As an example, internet-savvy property owners can easily obtain a wide variety of information on a county GIS site, but they must be educated to know that the property lines, contour lines, utilities, or easements overlaid on aerial photography may not be the accurate location on the ground.
It is essential that the “connected” GIS and surveying
professions collectively educate the general public and other users about the purpose for which the various data is “fit.” There has always been some misuse of data, but the opportunity for much greater misuse is present unless we continually work to educate the users.
“Data fit for purpose” can be one connection for the GIS and surveying worlds. Hopefully both professions will plug into this connection to benefit our professions and all the other users of this data.
While Janet and Randy may not see eye to eye on all surveying and GIS issues, they do respect each other’s perspective and point of view and attempt to “intersect” their professions whenever possible. Randy and Janet invite you to submit your questions to “Intersect.” Contact them via email at firstname.lastname@example.org or 919-417-0894.
About the Authors
Janet Jackson, GISPJanet is certified as a GIS professional and is president of INTERSECT, a GIS consulting firm.
Randy Rambeau, Sr., PLSRandy is a geomatics office manager with McKim & Creed, an engineering, surveying, and planning firm.
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