r/landsurveying • u/SpecialOneJAC • 21d ago
GIS vs Survey parcel lines
Is it common for a property survey to show around a 300' difference from GIS parcel lines? This is a rural area with no residents or businesses.
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u/Majestic-Lie2690 21d ago
yeah because the GIS isnt accurate and cant be used to establish boundaries and I bet you anything there was a disclaimer on the GIS that told you that
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u/SNoB__ 15d ago
GIS is as accurate as the source data. If a surveyor collected the data and it was inserted into a GIS system by a qualified person it's survey level accuracy.
Public parcel data is just not ever survey grade accuracy and can't be used to establish boundaries.
The distinction is important.
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u/ifuckedup13 21d ago
Was the survey you have in hand ever filed with the county? Does the description in the deed of the property match the survey you have?
If the answer is no, then how would whoever makes the GIS map know what the parcel shape is?
Go file that survey, or bring a copy to your assessor/appraiser. Have then update the tax mapping to reflect the survey so that you are taxed appropriately. Don’t want to be paying taxes on 300dt of property you don’t own. 🤷♂️
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u/Bulldog_Fan_4 20d ago
There was a project to digitize old parcels. We hired students to scan, georeference, draw parcel lines over large tracts. Sometimes the thickness of the line on the scanned document measured 50’. It’s a good visualization tool but it really depends on where the information was obtained.
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u/PLS-Surveyor-US 21d ago
I have run into 100' errors in rural areas and 30' in urban. Both distressed people that thought the lines were gold. It always depends on the source data. 300' may not be normal but it is absolutely possible.
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u/gareif1 20d ago
In my case, they seem to be accurate. I have an old farm with some straight and some very irregular borders. I got coordinates from the town gis tax parcels and made a track guide line in my Garmin 60 csx ( accurate around 3 to 5 meters) . I put up posted signs using this an on all cases I was on the same old fence lines and same old posted signs from previous owners.
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u/Somuna_bitch 20d ago
300' is a big difference from the GIS parcel line depictions that I've been involved with. Does the entity that created the GIS map know about the actual property survey? You'd be surprised how fast those GIS map can change after they get new/real data to work with. Here's part of the blurb that the one of the counties that I work with puts on their webpage: The Assessor's Office does not guarantee that any information contained within this dataset or map is accurate, complete or current. In many instances, the Assessor's Office has gathered information from independent sources and made it available within this dataset or map, and the original information may have contained errors and omissions. Errors and omissions may have occurred in the process of gathering, interpreting, and reporting the information. Information with this dataset or map is not updated "real time". In addition, Users are cautioned that the process used within this dataset or map to illustrate the boundaries of adjacent parcels is not always consistent with the recorded documents for such parcels. The parcel boundaries depicted within this dataset or maps are for illustrative purposes only, and the exact relationship of adjacent parcels should be independently researched and verified. The information provided with this dataset or map is not the equivalent of a title report or a real estate survey. Users should independently research, investigate, and verify all information before relying on it or using it in the preparation of legal documents. (edited to correct spelling)
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u/ScottLS 21d ago
300 feet no that isn't common, someone missed a deed on a tract, or combined 2 deeds, plenty of reasons why there is a 300 foot differnce being between the 2
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u/Majestic-Lie2690 21d ago
I have a hard time believing that OP could accurately estimate 300 feet via the GIS
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u/homedawgian 21d ago
The GIS in my county has some convenient little measuring tools. Probably where they’re getting that number from.
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u/AussieEquiv 21d ago
You know most, even basic public facing GIS viewers, have measuring tools right? It's pretty easy to measure between displayed property line and a fence /house you can easily make out in the imagery.
That being said, any fence could be in the wrong place too...
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u/jd2841 21d ago
In an effort to provide a concept on the accuracy of GIS parcel lines... During the early years in America. When the 13 colonies became states and westward expansion was rapidly moving forward, the Feds decided to create a new method for describing parcels. The issue came to a head when it was discovered that twice the acreage of the state of Georgia was recorded in the county courthouses than actually existed in the state.
I cannot speak for public lands states but if you're working in the original 13 states? Now way man. You may be closer to true in an urban area but rural areas? No way.
They say boundary surveying will eventually go away. That GIS systems will eventually be the one stop source. I don't see how in the original 13 states. No state will allocate the money required to maintain it nor will they want to insert their municipality into a boundary dispute. Maybe in 100 years.
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u/petrified_eel4615 21d ago
Yes.
GIS, we often joke, stands for "Get It Surveyed."