Surveying, Mapping and GIS

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Cadastral or not?

Posted by Dave Smith On 12/10/2007 11:23:00 AM 7 comments

After hearing some recent trials and tribulations of a surveyor arguing a legal lot line adjustment with the county GIS department (same story repeated again and again all across the nation), it again underscores the issue of what is or isn't cadastral GIS.

In Pennsylvania, our State Law says,

“Practice of Land Surveying” means the practice of that branch of the profession of engineering which involves the location, relocation, establishment, reestablishment or retracement of any property line or boundary of any parcel of land or any road right-ofway, easement or alignment; the use of principles of land surveying, determination of the position of any monument or reference point which marks a property line boundary, or corner setting, resetting or replacing any such monument or individual point including the writing of deed descriptions; procuring or offering to procure land surveying work for himself or others; managing or conducting as managers, proprietors or agent any place of business from which land surveying work is solicited, performed, or practiced; the performance of the foregoing acts and services being prohibited to persons who are not granted certificates of registration under this act as a professional land surveyor unless exempt under other provisions of this act.
As such, what exactly does a tax map represent? It seems that many GIS departments hop back and forth between boxes, either arguing that it is not surveying, and only deals with a schematic showing taxation, but at the same time, argue issues of deeds and possession, enter their parcel boundaries using COGO, and so on.

Either it is, or it isn't. If it is indeed a representation of the cadastre - and after all, taxation is uniquely tied back to the parcels and their possession - then it needs to be properly treated as such.

If, on the other hand, it's not a representation of the cadastre, then perhaps it's in fact something which perhaps has no real meaning, merit or legal standing whatsoever.

If the former is the case, then it likely needs to be getting developed and maintained under the purview of a licensed professional land surveyor, per state law - if the latter is the case, then I believe the whole process needs to be re-evaluated.

I'll put this out there for debate, with the caveat that I did intend to stir the pot - I'm interested in getting others' earnest perspectives.

7 Response for the " Cadastral or not? "

  1. Surveying v. neo-surveying: now there's the real battle ;)

    In a better world, it would be all about the accuracy and precision of the data, not the piece of paper that certifies one to be a surveyor. Medieval practices die hard.

  2. When it comes to accuracy and precision of the data, it's also about physically locating the evidence in the field and tying it to other known reference points and so on, and reconciling this against senior parcels, discrepancies in deeds, and so on.

    It's not so simple as just entering deed calls into a COGO routine and eyeballing it on top of an aerial photo or existing GIS base map, or worse yet, digitizing or rubbersheeting old paper maps into a GIS.

    As far as that piece of paper goes, it establishes a yardstick of the professional's actual experience in responsible charge of similar projects, his education, and his actual ability to apply the principles and practice (via exam). How is that such a bad thing?

  3. Sean, from a professional's point of view (one of those guys with a 'piece of paper'), it's all about *who* certifies the data, and for what purpose. When we get that piece of paper, we also get a professional seal that, when signed, legally commits us to legislated standards of practice. Believe it or not, there's a lot of education, experience *and liability* behind those pieces of paper that we obtained.

    BTW (and this is Surveying 101), there is a difference between 'accuracy' and 'precision'. It's in fact one of the questions engineers and surveyors have to answer correctly before we are registered (medieval as this pactice may seem...).

    Rudy Stricklan, RLS
    Phoenix, AZ

  4. Ben says:

    In my rather limited experience, the quality of the data coming from certified surveyors is not the issue. I think everyone recognizes the importance of well trained and educated professionals being responsible (and legally liable) for field data collection. The issue is the reluctance of some in transferring such information to a digital format that is easy to integrate with enterprise level software. The difficulty in doing this (inevitably political) daily creates unnecessary work and limits quality on the whole for our users.

  5. Anonymous says:

    I am more interested in what the county's are required to maintain, in terms of a spatial database, according to PA Law. Are county's required to have true cadastral information as part of an enterprise IT system or is it OK to have the 'parcel picture' for visualization purposes, for which GIS is well suited? I think as long as you know the limitations of the data you should be able to do either as long as one has a well documented process and communicate it to the folks inquiring about the data. Practically, just getting the sketch lines off of the mylar (or linens or whatever)and mantaining the transactions in electronic format must be a good start. I am very interested in seeing where this thread goes as well as parcel based taxing is the primary source of income for local gov'ts in PA.

  6. Anonymous says:

    I agree with ben. Coming from 15+ years working with parcel data from the GIS side, the divide between surveying and GIS maintenance of parcels could be vastly diminished if the surveying community would establish and use some best practices on transferring their work to those that rely on it. Many seem to have to be dragged into electronic submission by local government ordinance. A start would be requiring an X,Y (Z) coordinate for every parcel corner, in a known and documented projection/coordinate system.

  7. Geo says:

    Can someone provide a definition of what is a cadastral basemap, and does that imply a certain (minimal) level of accuracy when a dataset is called a cadastral basemap?