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Surveys influence on GIS

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annctga
(@annctga)
Posts: 10
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I’m curious on how much a survey impacts the GIS? After a new survey was done in a 15 home community, the GIS significantly changed. Was this a coincidence or was it from the new survey? Do you all use the GIS in your day to day activities?

 
Posted : October 17, 2022 8:55 pm
Geoff Ashworth
(@geoff-ashworth)
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More than likely the change is because of the survey. There is a common joke that GIS stands for Get It Surveyed. Typically a GIS system is not as accurate as a survey. I read through your previous post about your neighbor. It looks like your county has a pretty good GIS and Land Records website. If you dig around you can view surveys for free, this is assuming on my part that you are in Shawano County, WI. 

 
Posted : October 18, 2022 6:38 am
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MightyMoe
(@mightymoe)
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Never, never, ever use the GIS for location. It's gotten much better over the years for ownership, addressing, structure details, tax info, but for location it's not a go-to resource, more of a getting started for job set-up. 

 

 
Posted : October 18, 2022 6:48 am
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holy cow
(@holy-cow)
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Land surveyors will try to access all bits of information that can possibly assist them in doing their work correctly.  They understand, however, that not all information is valid until proven to be so.

GIS professionals SHOULD be using all data they are provided that has been developed by professional land surveyors.  The catch is, though, that a survey of a single lot in a subdivision does not necessarily have any impact on the other lots, in general.  

 
Posted : October 18, 2022 7:12 am
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Rover83
(@rover83)
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The bottom line is that a GIS and a survey are related, but serve different purposes.

Surveys focus on delineating a particular piece of real property as it lies upon the ground. It may sound overly basic, but there is a LOT of work and analysis that goes into that determination, and that is essentially what a survey does. Surveys also have clearly laid-out minimum standards, whereas there are no statutory requirements dictating how rigorous a GIS dataset must be.

A GIS is first and foremost an analysis and planning tool, meant for high-level viewing of datasets overlaid with each other - generally to illustrate the relationships between different data and facilitate administrative decisions for the area which it covers. Overlaying flood zones with parcel lines, for instance, will help a city decide whether to create a new development zone or not depending on its likelihood of flooding.

While a GIS might be very accurate, its very nature allows it to incorporate many disparate sources, some of which are going to be far less than survey-grade.

And sometimes a single dataset (think property lines in your county) is going to have some discrepancies in them. GIS analysts can only work with what they have, so they make decisions about how to modify or update parcel lines based on what are effectively arbitrary rules, which vary from area to area. Also, the very nature of a moving earth and inherent random error in measurement makes it impossible to rectify every single survey with each other across an entire county.

So the GIS folks try their best to make things "work together" for a parcel dataset, but there's only so much they can do. And because GIS is an analysis tool, not a survey, their goals are different than those of the professional surveyor.

 
Posted : October 18, 2022 7:39 am
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Ric Moore
(@ric-moore)
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I spent many years creating GIS datasets for local agencies helping them in managing their assets.  I typically refer to GIS data as "informationally accurate" and less about "positionally or spatially accurate".  The emphasis is primarily on access to the information and how that relates to its geographic relationship with other data.

 
Posted : October 18, 2022 9:18 am
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Norman Oklahoma
(@norman-oklahoma)
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Presumably the GIS keepers updated the boundary lines shown with data that they believed was more accurate than what they where previously showing. But under no circumstances should a landowner rely on GIS lines as boundary lines. They are simply never precise for a variety of reasons. Many parts to that puzzle.

 
Posted : October 18, 2022 9:18 am
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Bruce Small
(@bruce-small)
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If I find the GIS lines are nothing like reality (sometimes a hundred feet away) I send the Assessor my survey AutoCAD file and they correct their lines. Win-win all the way around.

 
Posted : October 18, 2022 10:01 am
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annctga
(@annctga)
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Topic starter
 

@geoff-ashworth Thank you, yes we did that and the County suggested we get a survey, which we did. I was really in shock to see how much the GIS changed after our survey was turned in. I wasn't sure if one survey could do that but the timeline seemed to fit.

 
Posted : October 18, 2022 10:03 am

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annctga
(@annctga)
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@ric-moore A group of owners hired a surveyor because most other surveys were done one one property in our shared community. I was really impressed with our surveyor and the detail and time he put into the survey. We had so many conflicting surveys prior to this one. All of the owners who hired this surveyor, only wanted accurate results, even if it was unfavorable to our property. Some of you were pretty harsh about my other post asking about ethics but that did not involve my property. I was simply asking because I didn't think my elderly neighbors should have been treated that way. That situation was a catalyst in our decision to hire a surveyor to survey our shared community. We have two neighbors in the construction industry that did not pull permits and we believed they built into our common area (Lot 11). Now we have confirmation they did. Also, their surveyor did have his license suspended in the past and he is currently under investigation. I'm assuming for the survey at the elderly couple's house and for the surveys he performed around Lot 11 because the investigating agency called us, as well as, the elderly couple. Ironically, the day after our survey, WE Energies sent a surveyor out. I thought it was our surveyor again so I went to talk to him. Coincidentally, our power lines are going to be buried so they had to survey our shared community. That surveyor immediately noticed an issue with Lot 11 around my house and further down. I believe he identified the same issues our surveyor had. Unfortunately, now we have to figure out a resolution because we don't have a HOA or any rules here. We basically relied on our local zoning ordinances for setbacks, impervious surface, permits, etc. Everyone else obtained permits but the two construction owners in the community didn't and now it's a mess.

 
Posted : October 18, 2022 10:54 am
holy cow
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I am assuming the surveyor that created the plat provided spent a great deal of time in communication with the surveyor who had been around previously.  If not, this battle may be a long way from over and done.  There should not be so much disparity in the work of two licensed land surveyors.

 
Posted : October 18, 2022 11:12 am
annctga
(@annctga)
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Topic starter
 

@holy-cow Plat was created in 1924 but surveyed by the same person over the years. Our surveyor did reach out many times and the other surveyor never returned a call. The WE Energy surveyor told me the same thing. I do know that the We Energy surveyor and our surveyor did speak.

 
Posted : October 18, 2022 11:18 am

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Peter Lothian
(@peter-lothian)
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I don't know what your laws are with regard to zoning violations. In Mass. I believe zoning violations can be enforced with fines and removal orders for up to seven years after construction. After that time, they may be protected against sanctions from the zoning officials. Your state will certainly be different, but it may be worth looking into. If you have any legal claim to Lot 11 (common ownership with others, a use easement, etc.) you should have standing to file a complaint about the setback violations.

 
Posted : October 18, 2022 11:21 am
hpalmer
(@hpalmer)
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@ric-moore  GIS data as "informationally accurate" and less about "positionally or spatially accurate".  very well said.  

Recently had a title professional tell me my survey was wrong because it did not match the tax map.  They rely on the GIS map.  I called the owner/attorney of the title company this morning about a deed containing 3-parcels of land and they indicated they would not insure one parcel lest we subdivide same.  The irony is this all appears to have started with the GIS map.

 
Posted : October 18, 2022 11:49 am
Ric Moore reacted
Ric Moore
(@ric-moore)
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@hpalmer Also appears to indicate a less than experienced title officer.

 
Posted : October 18, 2022 12:51 pm
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