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Jitterboogie
(@jitterboogie)
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November 8, 2018 8:00 am  

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! 

 


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mkennedy
(@mkennedy)
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November 8, 2018 10:20 am  

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

Melita Kennedy
Coordinate reference system and transformation specialist at Esri


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Norman Oklahoma
(@norman-oklahoma)
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November 8, 2018 10:40 am  

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.  

This post was modified 2 weeks ago by Norman Oklahoma

"Convention is like the shell to the chick, a protection till he is strong enough to break it through." Learned Hand


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JKinAK
(@jkinak)
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November 8, 2018 11:23 am  
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.

- John


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Dallas Morlan
(@dallas-morlan)
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November 8, 2018 12:47 pm  

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. 

Dallas P. Morlan, P.S. (Retired), OH, WV


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Jitterboogie
(@jitterboogie)
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November 9, 2018 8:24 am  
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
(@steve-emberson)
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Posts: 201
November 9, 2018 12:28 pm  

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
(@jitterboogie)
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Joined: 8 months ago
Posts: 180
November 12, 2018 4:51 am  
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
(@steve-emberson)
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Posts: 201
November 12, 2018 5:37 am  

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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MightyMoe
(@mightymoe)
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Posts: 5673
November 12, 2018 6:41 am  

Most GIS systems I'm familiar with have the water pipelines located and put into the mapping.  Are you saying when you try to place the descriptions on the GIS map they miss the existing pipes? I can see where that could be an issue when layering SPC bearings over the description bearings which may have a different basis. That is one of many reasons why property surveying can be difficult. It's critical to take each easement for what it is, how is it placed on the ground and why. 


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Jitterboogie
(@jitterboogie)
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Joined: 8 months ago
Posts: 180
November 14, 2018 3:57 am  
Posted by: MightyMoe

Most GIS systems I'm familiar with have the water pipelines located and put into the mapping.  Are you saying when you try to place the descriptions on the GIS map they miss the existing pipes? I can see where that could be an issue when layering SPC bearings over the description bearings which may have a different basis. That is one of many reasons why property surveying can be difficult. It's critical to take each easement for what it is, how is it placed on the ground and why. 

Sort of.  By using the ortho-imagery, and collecting diff-corrected RTK, I can realize 0.5' accuracy.  When I attempt to depict it in our Maps, the created version of the parcels created by our county doesn't tie out to the imagery at all, nor does the PLSS that is also depicted.  I ground truthed the corner, the structures etc at a recent collection location and verified the corner ties with the Mon-Recs.  

Big goal is we are going to probably create our own independent maps from the county, to provide our internal maps and then those provided the community with much better visual accuracy.  Nothing will be used for replacing real Land surveys to define and delineate the true on the ground locations of the easements. I'm in GIS.  It still stands for "Get it Surveyed" and always will for me.

Thanks again for any and all comments.


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Bill93
(@bill93)
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November 14, 2018 7:36 am  

The discussion of B.O.B. issues makes me wonder again why it is standard practice to give a bearing on each line.

Why not corner angles? If you use a transit or total station that's what you measure.  If you use GNSS you measure (relative) coordinates and compute either bearings or angles.


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