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.