The maxim in the surveying community of "GIS = Get It Surveyed" is still alive and well, where cadastral GIS is concerned.
Some GIS horror stories du jour:
- Community in New Hampshire that's assigning parcel IDs to gaps and overlaps found in their GIS system
- A county in Oregon that took the above one step further, and actually decided to try and auction off those gap and overlap "parcels" (fortunately the county surveyor stepped in and advised them otherwise)
- Central New York state - a county tax department assigned parcel status to a gore area and the county auctioned it off, created many problems.
- A county in Virginia that was fighting to keep their GIS data over that of actual survey data in the case of a discrepancy, strictly because the assessed GIS acreage was more than the actual acreage owned, resulting in more income for the county
- And the most ridiculous of the lot - a county in Texas, that when they couldn't locate the current owner of the parcel, rather than researching it and resolving it, they filled it in with a fictitious name - "Arnold Ziffel".
When it comes to cadastral GIS, I've said it before, and I'll say it again - land surveyors still are and will always continue to be the domain experts when it comes to resolving property line location, relationship to adjoiners and senior ownership, chain of title, relationship to found evidence in the field, and toward discrepancies, gaps and overlaps. Let's also throw understanding of rights-of-way, easements, road dockets, riparian rights, PLSS and the like, and how these likewise affect and impact ownership and taxation.
If you have discrepancies, data gaps, quality issues, other issues, I cannot stress it enough to county tax departments - work with the surveyors. Some counties are very good about this- others are downright frightening if not dangerous.
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That's why I took all the GIS and surveying courses in the civil engineering department in college: To know what to stay away from and to know enough not to be dangerous.
Dave, always good posts. Would you happen to have any links to these horror stories? I'm giving a presentation later this spring at our state Land Surveyor's Conference, and they would be most interesting to have more details on. Lacking specific references, do you have any problem with quoting your blog in my presentation?
Regards,
Rudy Stricklan, RLS
Phoenix, AZ
I've been working as a GIS Manager in local government for over a decade now and we point to surveyors when property line disputes arise. Your horror stories may be just that, but I don't think they are representative of the majority of municipal parcel layers across the country.
I hope that the theme of your post wasn't to specifically criticize the accuracy of all GIS data. Lord knows we've had our backroom stories about the few surveyors that claim to be mapping Gods. As a GIS professional, I highly respect the surveying profession and hope that we'd garner the same respect in return.
Thanks,
-Midwest Mapper
Midwest Mapper, the intent was NOT to specifically criticize the accuracy of all GIS data, it was to heighten awareness of some of the serious issues and problems that have arisen when faulty GIS data has been used in place of land surveys. I would anticipate that the types of occurances that I cited in my article are somewhat isolated.
Indeed, as I mentioned, many tax mapping offices do work closely with surveyors, however there are also many GIS departments out there who have their own opinion of themselves as mapping Gods.
It comes down to due dilligence - any surveyor will tell you that it's no simple matter to reduce an entire county's worth, and perhaps hundreds of years worth of data to a common, coordinated cadastre, and it's often easy to fall into the trap of chasing ones' tail around and around in trying to get parcels to fit. Here, the surveyors can assist and work cooperatively with tax mappers in providing depth and background on senior parcels and known, reliable points of reference, to avoid pitfalls such as rubbersheeting good data on top of bad data again and again.
Some of the municipalities in question:
Town of Hudson, NH
Montgomery Co., VA
Deschutes Co., WA
Houston Co., TX
As another GIS Manager in local government, I wholeheartedly agree with Midwest Mapper. I go to great pains to stress the importance of proper legal surveys to public officials, staff, and the public when issues similar to those in the post have come up.
I also have great respect for surveyors and don't understand why there needs to be any animosity between the surveying and GIS professions. I've actually thought at times about starting on the path to become a PLS since I've come to see it as a tremendously valuable credential to have as a GIS professional in local government.
I'm an environmental professional that only dabbles a little in GIS and followed a link from "The Map Room" module on My Yahoo. So, I'm not that up on GIS Lingo.
What is a "Gore Area"? Some sort of overlap?
Thanks
P.S. I ran the phrase through a search engine and it pretty much just brought me right back to this blog.
A gore is more like an "underlap" (couldn't resist, sorry). Dictionary says triangular piece of land. Although not in my dictionary, the triangle between two merging roads where you aren't supposed to drive, but is paved just in case, is called a gore. To answer the question in the context of the comment, it would be a triangular piece of land between other pieces of land or just a triangular piece cut off of a piece of land (these really amount to the same thing).
Anonymous does not quite have it right. The gore is a point, not an area. The gore is the place where the two roads meet. There are two types. There is the physical gore, where pavement of the ramp meets the pavement of the main road, and the virtual gore, where the white edge line paint strips converge. Anonymous defines the gore as the area between the physical gore and the virtual gore.
Nice post....
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