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Jitterboogie
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So I have the dubious expectation of drafting and plotting the easements for the Municipal water, storm water, and wastewater for the city, for which I gladly see as great work to gain knowledge of the system, and build the appropriate maps and asset management system too.

The County seat, (my city) is clearly in the North State plane region, however the agreed upon coordinates are Central, by a decision that predates me.

I'm collecting the Section Corners( and all other data) with our VRS RTK(fancy) for real world GPS locations to apply to our 3" map imagery (fancier still...) and they tie out amazingly well, due to the preponderance of photo identifiable objects like trees, valve boxes, curbs etc..

Of course, GIS stands for "Get It Surveyed", and from whence these legals I draft from are surveys, I have apprehension when drafting the maps because the county supplied data is clearly not in line with the images, and a rift is potentially going to open up when I start to tome on about this in my prolific emails about what I keep seeing.

I was told this decision to use Central versus North was based upon a state law that I still have yet to uncover that describes the setting.  Any Surveyors that have any information regarding this would be greatly appreciated to PM here just to give me more feedback so I can learn more about what I clearly don't know yet, and gain some insight. 

Thank you all in advance! 

 

11 Replies
mkennedy
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North vs Central zones means that the map projection is Lambert conformal conic. There shouldn't be any problem with the math even though you're working outside the zone. However, distances would certainly be affected. Does the software you're using for the map data allow on-the-fly conversion to another coordinate reference system? You could try editing in the Central zone and see if that makes a difference. The software should convert the edited feature to the North zone when it saves it to the database.

Melita

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Norman Oklahoma
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Your chances of getting some specific information about your area would be greatly enhanced if you told us what area  you are in.

Speaking generally state GIS systems sometimes adopt one zone for the whole state. In Oregon, where we have  only the two State Plane Zones, the GIS has defined it's own zone to cover the whole state. Your state apparently has 3. I'd guess that they, the GIS people, have simply adopted the central zone as their one zone for the whole state.  

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JKinAK
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Posted by: mkennedy

There shouldn't be any problem with the math even though you're working outside the zone. However, distances would certainly be affected. ... The software should convert the edited feature to ...

Melita

Draw it up in any geodetically referenced coordinate system that reasonably matches ground distances for your average area of interest (some LDP or the North Zone or ?? - or even multiple projections if you are in an area with lots of vertical difference) and then transform it to whatever coordinate system is expected. Even though the transformation can happen on the fly in many programs, you'd be better off transforming it in global mapper or some other robust software so that the deliverables don't confuse the client.

Doing this will:

  1. Minimize your effort by allowing you to use the ground distances on the source docs;
  2. Minimize the potential for math errors;
  3. Be infinitely reprojectible;
  4. Be understandable by reasonably knowledgeable end users.

Since all your source data is probably on a jumble of BOBs, you'll still need to rotate the source linework for each granting document to match your parcel fabric (assuming it's based on surveyed lines) or to found mons if you have them or (and this is the least desirable) if the parcel fabric in the target GIS is of poor quality - just deliver the data with record bearings - there's only so much you can do.

Whatever you do - document it well and make sure it's in the metadata so that your work has a long and prosperous life.

Sounds fun and potentially profitable.

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Jitterboogie
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Posted by: JKinAK

there's only so much you can do.

Whatever you do - document it well and make sure it's in the metadata so that your work has a long and prosperous life.

Sounds fun and potentially profitable.

Profitability is out the window because I work for the municipality that's trying to gain some ground with my (and others) knowledge.

I agree, there's only so much you can do, but, it still has to appease the tax payers and the stake holders of the technology that was purchased to" make it better".

 

And thank you to everyone that responded, I greatly appreciate tapping into this knowledge base, it has a great depth and variety.

 

I work in the Front Range, live in Fairplay.  I have enough land surveying work history to know what I don't know, and same with GIS.

Its just another situation where someone made a decision that they fully didnt understand, and now I get to make waves, or tow the " we always do it this way" mentality. Blah.

Doing it right is the only way.

 

Thanks Again and I'll keep you posted on how the whole thing rolls out.

 

J

 

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Steve Emberson
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Off topic, but how is Ski Cooper? I've read alot about it and I really want to try it. I've hit all the Summit County mega resorts and prefer A-Basin to them. I used to really love Winter Park until it out grew me as well....

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Jitterboogie
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Posted by: Steve Emberson

Off topic, but how is Ski Cooper? I've read alot about it and I really want to try it. I've hit all the Summit County mega resorts and prefer A-Basin to them. I used to really love Winter Park until it out grew me as well....

Haven't skied there for a while, but its a bone fide ski your A$$ off small town ski area.  If you want a real treat, take the Chicago Ridge trip in the Cat. Not cheap, but better than waiting in line with the hordes in Vail.

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Steve Emberson
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Thanks for the reply. I like the history of it and it not being so damn pretentious. I'm thinking our next trip west will be there. Would Leadville be best to place to find a place to stay?

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Dallas Morlan
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Original Poster's profile location is  Fairplay, CO and I presume this is the city where he is mapping utilities.  As noted above the granting documents will likely have a "jumble of BOB'S' (Basis Of Bearings) to deal with.  I have found that outside of the surveying community many do not understand that historic title documents do not use a single north.  I note you have a GIS certification and presume you understand the difference between geodetic (true) north and projection grid north.    You will likely be dealing with many documents developed by engineers or lawyers. 

I once had a Professional Engineer argue that "North is North is North and you can't change things from the deeds and easement documents."  Field survey had located all the monuments a long a single line common to three adjoining properties.  All distances, both in the deeds and on the ground, checked yet the bearings differed by several degrees.  The engineer wanted to show only deed bearings on the maps for utility easements maps and in the new easement deeds.  Requirements in the contract required all documentation to be tied to and bearings to be based on the correct zone of the state system.  Never did get him to understand we were dealing with four different Basis Of Bearings on just this portion of the project. 

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