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Epic Battles: GIS vs. Surveying?

Posted by Dave Smith On 7/05/2008 11:15:00 AM 9 comments

Discussion revolving around a planned, but retracted article on GIS for Professional Surveyor Magazine has led to a lot of interesting discussion, but to me generally reveals a continuing underlying tension and misperceptions between the GIS and Surveying communities.

Adena Schutzberg / All Points Bulletin: Update: State Licensing Board "Censors" GIS Article
James Fee / Spatially Adjusted: "GIS Practitioners as Doing Work Surveyors Should Be Doing"

While these articles post updates and amendments, based on comments by Tom Gibson, Professional Surveyor's editor, which clarifies that the author decided to retract his article, the underlying question of GIS versus surveying and legal jurisdictions still remains.

Some of the comments are telling - with perceptions and suggestions that State Licensing Boards are somehow cracking down in draconian fashion, demanding censorship and attacking GIS practitioners. Tied into this, we had the MAPPS lawsuit (another issue which I believe will resurface at some point), overlap of surveying with photogrammetry, and other issues. Meanwhile, in the surveying community, we still hear "GIS = Get It Surveyed".

I have my own, perhaps unique perspectives and insights, being a GIS practitioner since the late 1980s, as well as a licensed Land Surveyor, and finally, also serving as chair to a State Licensing Board.

Note: Having said this, please note that my comments to follow are my own personal views, and are not to be taken as official statements or in any way representative of our State Licensing Board's views.

For most GIS practitioners, they readily defer to surveyors' knowledge and domain expertise on cadastral issues - matters of how property boundaries are properly dealt with, and so on - and similarly, most surveyors know their limitations when it comes to GIS. However, there still seems to be occasions which give rise to confusion and misperception.

One basic thing that we all need to come into reckoning with is that Surveying and GIS overlap, but that neither is wholly contained within the other, and that each has areas which may additionally be mutually exclusive from the other. Another part of this Venn diagram equation is Photogrammetry - another topic, which has come up often. I have best seen it illustrated as such:

One area of contention is that some states' Practice Acts are very broad in their definition of what constitutes land surveying - e.g. "measurement and determination of any feature on the earth's surface" - which might not be appropriate for the strictest of interpretations. Many everyday GIS efforts could constitute surveying practice under this definition - but is it appropriate?

If one considers typical State laws pertaining to licensure and practice of land surveying, one will see that the primary objective is in protecting the public, it has little to do with protecting the surveying profession.

So what is falls within the purview of licensing boards, and what falls within the definition of land surveying, toward preventing harm? That may vary somewhat from state to state.

But how might the public be harmed by GIS data, as opposed to proper land surveys? Here are some generalized versions of recent tales I've heard:
  • A county tax mapping office, where a GIS practitioner "helps" a realtor friend in a bind by preparing a property description based on lot lines in the GIS. Where did those lot lines come from? Combination of digitized paper maps, lines rubbersheeted to apparent fencelines on orthophotos, and so on. The harm? This description brings with it apparent legal connotation, as a representation of lines of ownership. The buyer may be getting a misrepresentation of what the lot's actual extent and location is.

  • A municipality orders a homeowner to demolish and remove a brand new addition, based on their perception that it is in violation of setback lines - based on the GIS.

These things can be only be remedied through a proper survey. One definite question that should be asked, is whether litigation or legal action might ever be a possibility. If it's anything relating to or impacting property ownership and use, such as property boundaries, rights-of-way, easements, or things of that nature, one would definitely want reliable, accurate survey data that can hold up in a court of law. Most county GIS systems will not pass this test.

Perhaps there a jurisdictional issue at stake, such as wetlands delineation (where US EPA, Army Corps of Engineers, State Environmental Protection Agencies or others may or may not have jurisdiction, based on whether or not the land in question is a wetlands or not). Given an instance where a wetland may have been filled, drained, or otherwise encroached upon, and where the original physical evidence of plants, hydric soils, and wetlands flags may no longer exist, a surveyor's location of and ties to the wetland biologists' flags is far more likely to hold up to scrutiny, be accurately retraceable in the field, and be defensible in court than GIS data from recreational-grade GPS receivers or other approaches that are occasionally seen in use.

Or a toxic waste spill - whether it impacted adjoining properties or not - and so on. The same circumstance may come into play with other jurisdictional issues, such as taxation and municipal jurisdiction, and other areas.

Is it a specific legal requirement that these types of data be collected by surveyors in these cases? To turn that question around, in these cases it's instead a matter of basic good practice and adequate protection from dispute and liability as to how the locational data is captured.

Not every GIS practitioner has to deal with these things - but some do very much need to be cognizant of it. And certainly GIS practitioners do need to be aware of state Land Surveying Practice Acts in any regard. Ambiguities will not be resolved overnight - certainly questions of "what DOES that cadastral GIS system really represent" will continue to come up again and again. And certainly many stewards of cadastral GIS are aware of this, and put as many protections in place as they are able to - such as disclaimers and metadata, but for most citizens and casual users of the data, the phrase "consult the metadata" will only lead to glazed eyes. And while GIS systems are fully able to accomodate survey-grade data, and while some nations have made great strides toward a coordinated cadastre, here in the United States, the approach has been far more piecemeal, with varying degrees of robustness in how cadastral data can be improved. I have suggested record-level metadata for parcel data and similar approaches to allow refinement, where good, vetted, survey-grade locational data can be utilized and held toward iterative acquisition of a uniformly high-quality database. The locational accuracy of each parcel and subdivision can then be assessed on a case-by-case basis. Additionally, database linkages to plats and other survey data can be put in place.

Certainly not easy questions to answer overnight - but also hopefully I can share more insight and reality than perceptions that "Surveyors are trying to take over GIS".

Update: To follow up, I've put together and posted a "Compendium of State Land Surveying Practice Acts" with links to a number of jurisdictions' laws relating to the practice of land surveying.

9 Response for the " Epic Battles: GIS vs. Surveying? "

  1. Anonymous says:

    Very nice article. Meta data at record level ? interesting..

  2. surveying supplies says:

    GIS actually becomes surveying A licensed surveyor is responsible for published geodetic data, because boundaries have economic implications. For instance, a landowner wishing to build a house needs to determine the distance from a wetland to the proposed building site, which can impact the land's economic value tremendously. The landowner can hire a biologist to determine a wetland boundary using soil and plant indicators, and a surveyor to determine the distance from the wetland boundary to the building site. If, on the other hand, the landowner hires a GIS specialist who uses a high-quality GPS unit to determine the wetland boundary, the GIS specialist is now responsible for that information. At issue is the protection of the public, who may be harmed by incorrect information, and the fact that unqualified individuals are using information that is not survey-grade to make decisions that impact property values. But this is the case regardless of the use of a GPS unit, so when does GIS become surveying? One deciding factor is the purpose for which the data are collected. Generally, collection of geographic data used for inventory or reference and stored in a database is not considered surveying, nor is transformation of already-published position data or non-public data. There are several other factors as well

    Great article.

  3. Interesting post. I think this is a well written article which helps to gain the knowledge of tracking and surveying maps.Digital mapping services also plays an important role in this field.
    The power of GIS can not be underestimated and easily understood such that every sector has come to embrace it. The GIS is our future,hence it is necessary to study by students and analyze information and data.
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  4. Anonymous says:

    What I find most interesting in this debate is that surveyors continuously point out various opportunities for public harm or tell anecdotal horror stories, but rarely document real cases where irreversible damage has occurred. As a GIS Professional I certainly agree that we need to clean up our act on data standards, statements of accuracy and documentation. However, I'm not convinced that licensing, particularly as a sub-discipline of surveying is the only answer. If we are headed toward a GIS license, the surveying community must make room at the board level for our input and oversight. We're not going to accept anything less.

  5. When buying a property or a building you may be grappled with many uncertain situations such as whether the property boundaries are accurate or whether the neighbor's boundary or fence is at the correct position.Why you need a property or boundary survey? The boundary survey will essentially capture all the encumbrances pertaining to boundary or fence lines. if you buy a property without taking into account of the problems associated with the property, you will certainly going to face unnecessary costs, litigation and delays.Land Surveys

  6. Anonymous says:

    It's neat to see how surveying and GIS relate to each other. I think that it is important that if you are doing any kind of land work, that you have it surveyed first. You wouldn't want to start construction on a bad plot of land.

  7. if you want to link all of the deeds, easements, and quit claims sure, YOU foot the bill. the state government will not. In Nashville ,its was last to get computers instead of micro film!
    Furthermore, there is no linking of sub divided land from its original boundaries to the parcels now. I've seen bad engineering drawings, surveys, and not to mention the ever wrong tax map, when legal descriptions get written nobody's there to see if it closes. So go right ahead and garble the american dream up further, best to keep taking pictures!

  8. I have gone through the site and read all blogs and this is a nice one:

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  9. The definition that brought up about land surveying was one that answered my question. I have been thinking about it before and even wanting to know what constitutes as land surveying. Mainly because a neighbor of mine talked to me about him surveying my land for next week.