Conversion of the Digital Parcel GIS Map to Survey Grade Acc

This scenario is a problem for both surveyors and planners.
Surveyors need to sell the value of their services for GIS.
Planners realize too late the value of a GIS controlled by
accurate survey control. The rectification of how subdivisions
fit into the accurate survey control, is expensive.

> 1. Will land surveyors accept, understand and use this new technology?
I think the more pressing question would be will the land industry related professionals such as engineers, architects, and lawyers use it, and my guess is that they would. But to answer your question, yes, history demonstrates that as a group land surveyors have been willing to accept and use data resources developed by others.

> 2. How can land surveyors use this new technology to avoid becoming obsolete?
The premise of your question being that they can use this technology to avoid becoming obsolete? Maybe. I think that we have seen a dimunition of the need for our services already and I think it will continue. If the scenario you've outlined comes to be, and in most ways it probably will, then yes, we can expect the need for our services to be severely reduced. Permanent obsolescence? No, there will always be some parcels whose tax map representation defies translation to anything meaningful, and also there will also be the need for a few experts to guide the public through the process to derive useful data from the public digital cadastre.

> 3. Is it too late for land surveyors to participate in these conversions?
For the bulk of our profession, yes, for a select few, no.

> 4. Will the interrelated web of all of the parcels in these Parcel GIS Maps act to reduce litigation over disputed boundaries?
Probably, albeit possibly for the wrong reasons. The public will look at the digital coordinated cadsastre and see one line between themselves and their neighbor, which of course, is correct, their is only one. I imagine they will view the location of the line as being more conclusive and authoritative than it really is, and thus be less inclined to dispute it. Many adjoining owners will rely on the location of the line to settle their disagreements.

Stephen

Does Alachua County have coordinates that are sufficient for most if not all boundary survey needs? If so, is there any documentation that I can review?

> This scenario is a problem for both surveyors and planners.
> Surveyors need to sell the value of their services for GIS.
> Planners realize too late the value of a GIS controlled by
> accurate survey control. The rectification of how subdivisions
> fit into the accurate survey control, is expensive.

:good:

Stephen

I really like and agree with your assessment.

Ralph

Those Are Not Indisputable Facts Ted

"My Ph.D. research at the University of Florida since 2003 shows that today almost all counties (parishes) in the United States and in many other countries now own and maintain public Digital Parcel GIS Maps (“Parcel GIS Map”) which were usually created from the hand-drawn tax maps and other recorded information. (1)Additionally, most jurisdictions also have a relatively current, high accuracy, digital, aerial orthophoto mosaic (2) which can be viewed on the internet as an overlay on its Parcel GIS Map.
Many of these Parcel GIS Maps are now in the process of being rectified by ground data such that the corners and lines more closely agree with the aerial orthophoto mosaics and “ground truth.” Once rectified, these Parcel GIS Maps can produce state plane coordinates (and/or latitudes and longitudes) sufficient to produce boundary maps for most, if not all, boundary requirements. (3)
Survey grade GPS allows for the use of this coordinate information to locate corners and lines on the ground. (4) As this high grade GPS becomes more available to the public it is inevitable that within a short period of time this new technology will cause the traditional boundary surveys by licensed (registered) land surveyors to be unnecessary. (5) Given these indisputable facts ...":excruciating:

(1)I have worked on tax maps and the quality of previous work within them is abysmal.

(2) I have yet to be able to recognize a set property monument in such a photo.

(3) Relative precision of 0.1' and you can prove it? Simply not possible in a State Plane Coordinate system.

(4) Survey grade GPS can find previously located survey grade GPS points on the ground. Where is that original data?

(5) More surveyors will be required as land owners and other non professionals with GPS create boundary disputes.

Has you PhD dissertation been submitted for approval? Be cautious as a fraudulently obtained PhD is worthless in Court against a surveyor that understands the truth.

Such a 10,000' by 10,000' orthorectified photo requires 200,000 by 200,000 recognizable pixels and a corner marker would be only 1 pixel. Lots of luck with that.

Paul in PA

Ted...

This problem surfaces occasionally....

Boundary location is NOT merely a function of mathematical precision. Mathematical precision may help locate or relocate a specific land boundary and can do wonders for recordation. But boundary determination requires much more than precision and stored memory.

Ted...

:good:

Since you've dropped this in 2 forums...

Ted you forgot a major question: Do counties want the massive increase in legal exposure for this? Of course not. Those counties that think they are capable of producing proper boundary surveys via GIS simply cannot. They just do not have the experience to understand the intricacies AND implications of boundary law.

I believe one needs to recognize there is much more to boundary law than making layers in ArcGIS snap together in parcel fabric with a suitable closure ratio.

When a county goes into a battle with "indisputable facts", they best make sure they have all of the facts. If they miss one important detail in the field or the chain of title they will quickly find themselves spending the equivalent to their budget for new photogrammetry every 3 years on one single expensive lawsuit... Are they ready for that risk? Most I know are very risk averse. :excruciating:

GIS as boundaries

Dear Mr. ted.madson,

I have been acquainted with your work (if this truly is Ted Madson) for more than 30 years now and I still have a copy of your book "The Mathematics of Land Surveying", which I believe to be required reading for one just beginning in land surveying.

However, the postulate you posted here is so flawed that it is absurd. Your indisputable "facts" are only fodder for what, I presume, is your attempt to create a discussion designed to help others acknowledge and react to a scenario which you believe is going to occur in the near future.

1. Absolutely no "ground data", as you put it, includes the location of property monuments with the precision of survey grade information.

2. While I am not intimately aware of all GIS systems in the U. S., I can attest to you that the counties of Harris, Montgomery, Ft. Bend, Liberty and Galveston, Texas along with the cities of Houston, Galveston, Stafford, Missouri City, Conroe, etc., do not and will not, in any forseeable future, begin to use survey grade GPS or any other measuring system capable of survey grade accuracies for the location of ANY planimetric features, either new or existing.

3. Your implication that aerial imagery is accurate enough to be used for land surveying is patently false. There is no extant technology that allows images to reflect survey grade precision.

4. What makes you think that the public will be able to acquire survey grade GPS for general use in the near future? I have seen nothing that indicates that GPS prices will drop to the point that anyone will be willing to purchase survey grade GPS equipment

5. What makes you think that the public will take the time that we, as protectors of the public good, users willing to accept the liability which our profession demands, users willing to spend thousands of dollars and weeks of our time to learn and understand the proper methodology and procedures to be used with this technology, have taken?

6. By the way, have you ever looked at the disclaimers placed on every page of a GIS Parcel map? They very clearly state they are for information or planning only and cannot be used for boundary purposes. For anyone to use these as boundary maps, the GIS will have to approve such. That means THEY will be liable for boundary disputes. That will never happen.

But thanks for the opportunity to discuss a topic that is science fiction at this point and will be for a long time.

sincerely,

Jack Chiles

There has to be a happy median, Some GIS departments already "think" they can do this. and the public "thinks" that the "county" is correct. Example: A few weeks back i get a call from a lawyer,

Lawyer> you did a survey that is wrong and need to correc it.
Me> what makes you think it is "wrong"
Lawyer> The GIS department said it was, it won't fit on their maps correctly.
Me: what was the date on my survey?
Lawyer, April 15, 1995.
Me> well i laughed so hard i barley could stop. I told him to have the gis department get a sureyor to survey it and if he had a problem he could contact me and we would talk about it.

oh by the way, i was told by this lawyer that it is my mistake and i wasn't getting compensated for it. so yes to Mr. Madsons theary, in part, The Gis folks think they can produce such maps and the public is eating it up.

[sarcasm]Tell the lawyer he is wrong about everything because the janitor at the GIS department said so.[/sarcasm]

I gave a subdivision on SPCS to the GIS guy at the Town. He overlayed it onto the data layer and said, wow, it matches pretty close. He decided not to go through the effort of modifying his parcels to meet the survey standard. That would be an actual nightmare for the one-man department. He will at least tell people the GIS is not good at a parcel level.

> [sarcasm]Tell the lawyer he is wrong about everything because the janitor at the GIS department said so.[/sarcasm]
>
> I gave a subdivision on SPCS to the GIS guy at the Town. He overlayed it onto the data layer and said, wow, it matches pretty close. He decided not to go through the effort of modifying his parcels to meet the survey standard. That would be an actual nightmare for the one-man department. He will at least tell people the GIS is not good at a parcel level.

I understand that all departments aren't like the one i described, if fact probably more like the one you described, but they are out there, and it is very sad.

It's not their job to make perfect assessors' overlays. That is why there is a profession called surveying.

It's the same concept as adding a coordinate on your plan instead of setting a monument. The basis of the coordinate must be described and as we should all fully realize, the earth is far from a static place. Here on Cape Cod, we are moving south east by about 0.5' per century. You publish a coordinate on a plan and in 20 years it will be off by 0.1' (of course, the reference monument should be off by a similar amount, but if some yahoo uses CORS the result will likely be off).

The static location of boundary lines misses the subtle nuances of boundary including agreement, acquiescence, adverse possession, and many other concepts Ted Madson writes about in his books. While many boundaries are semi-static, you cannot create an entire county without a full survey. How about when you find the little gaps and overlaps in the measurements? It's an overwhelming task.

Is there an upside possibility here?

One of best mechanics shops I ever used had the sign on the wall encouraging you to try it 1st, get frustrated and then call him. Those that did appreciated his professional/specialty services more.

I do not see boundary surveys by PLS's ever being replaced by the digital world.

Are our rules not deeply entrenched with very old law? Is there an APP for that?

I support working with GIS professionals, there is funding and work to be had here. Much of it is over and above what we have done in the past.

seems "Ted Madson" is trying to stir the pot, and doing a swell job of it.
Ted - stir often as to not allow facts to stick to the subject matter 😉

Geodetic quality photogrammetry has been done, but ...

it's extraordinarily expensive. Minimum requirement is 80% forward lap and 80% side lap so that each photo-triangulated point is imaged on 9 different photos, and each photo-triangulated point is targeted (paneled). Aerotriangulation software has to be the simultaneous bundle-block adjustment type with error propagation analysis. There ain't that many photogrammetrists around that can handle that sort of stuff.

Mere orthophotos? Not a chance.

You still will need that guy on the ground to figure out what to target. Sounds like a whole lot of work for a Land Surveyor.

Photogrammetry is an efficient tool, along with LIDAR. It's not a panacea.

Those Are Not Indisputable Facts Ted

:good:

I was thinking along the same lines as you.

I certainly see the combined data becoming more pleasing in appearance in my home county. However, they still have a tendency to take any line work I provide and 'adjust' it to look good with the aerial photos and other line work already in place. Which, as you point out, is not going to be of the accuracy needed for land surveying.

I use GIS at my office and am a big fan of it. Unless/until all parcels have been surveyed on or tied to a known coordinate system, the parcels data base will remain a pretty sketch with great uses other than determining property boundaries.

The O.P. is 19 days late.

> Once rectified, these Parcel GIS Maps can produce state plane coordinates (and/or latitudes and longitudes) sufficient to produce boundary maps for most, if not all, boundary requirements.
>
>

That's funny stuff!