My guess is two things may have happened. 120' sounds like a NAD27 to NAD83 shift. Is the error almost all east-west? It could be that the old control was originally run in 27 and somehow those lats and longs were used to calculate NAD 83 coordinates thus creating a 120' shift. I would reduce the coordinate (by coordinate I mean LATS and LONGS) using one of those guess and hope conversion programs like CORPSCON and see if by changing from 83 (your located #) to 27 you match a bit closer. If that's not it then someone did a "here" at the beginning of the project and it got carried through. 120' on a "here" point these days would be unusually far off, but back in the day (12 years ago or more) that was about normal.
I don't think you did anything wrong, but I would look into it a bit farther and then let the DOT know what you find.
Finally, why are they doing surface coordinates with a 1.000005 scale factor? There can be that much distortion in the job just from an elevation change of 120'.
Double check the Lat/Long of your base point in the controller vs. what TGO shows vs. what you think its supposed to be based on the start up of the project.
A couple of weeks ago a started a new project in TBC, which is a whole new animal to me. I went to the site up in the mountain in a high, very open valley. I set up 2 receivers and collected data (via RTK & Infill) and submitted to OPUS.
I created a ground projection and everything that I had tied out (PLSS and private corners) checked rather well. Even back checking against the SPC zone I was in. WE went back out and set up on the same point that I started the RTK & Infill from. I missed the 2nd control point by 4.5 feet, but the monuments were all within a few hundredths.
To make a long story short, I had disabled the OPUS coordinate in the TBC project and left the Infill point Enabled. Wrong LAt / Long in the DC.
yeah, the possibility of a datum shift occurred to me too.
> ""
> GPS doesn't really understand Cartesian coords, it understands Geodetic coords and converts to a Cartesian system strictly based on a set of parameters that you assign to it. I'm speculating because there is a lot of info that would take you pages to explain so I'm trying to gather the pieces right. I'm still curious as to your first procedure when you started the work...?...
> """
clarification, GPS operates on a Cartesian coordinate system X,Y,Z. check out a gps least squares adjustment, for example. there should be a report in it of the seven parameter transformation DX DY DZ RX RY RZ SCALE. not to be mistaken for the more common realization of North East Elevation.
it is commonly thought that gps operates in a lat lon ellipsoid, but at lon ellipsoid is a conversion of the xyz Cartesian coordinate system. the gps controllers are loaded with WGS84 and SPC converters, as are other realizations, reference frames, etc.
this doesn't answer the other,bigger problems, but i had to throw in my four hundredths
1894059.6972 x 1.0000057236 = 1894070.54 (1894080.54 Project)10 ft even?? typo?
691990.1573 x 1.0000057236= 691994.12 (691994.12 project)
I think MightyMoe is onto something. I also agree it is foolish attempting to remove half a hundredth of distortion per thousand ft. on a mile project. This project could have been designed and built on SPC just fine. I don't think it would have helped avoid this situation here however.
Re-reading your post a few times I don't see anything wrong with your process. So is your question how could the project coordinates get off so far? (who knows, lot's of possibilities) or how could you get off your map so far? Remember, you told your system you were in SPC so it assumed you were. When you pick your point off a map to begin the base it simply shows you how far off SPC you are by your non initialized position. Then "so I let it set for a few minutes, recorded the base coordinates, and they were off my point about 120'. " that makes perfect sense. It was pulling new base coords from the birds not from your project.
Yeah, that was a typo on my part, it is 80.54 on the plans.
The factor they used and put on the plans is obviously wrong, I think there's an extra 0 in there. However, without redesigning the entire job, I had to use it.
My question was how I was able to stake the whole job over a period of a couple of years without having any problem? How far off can SPC be from the actual Lat/Long before Survey Controller will not work? As I said, I didn't do any calibration, just set the base on the point and started it with the plan SPC.
Well then the plan coordinate doesn't check. The SPC coordinate calcs out to 70.54 using the provided scale from origin 0,0.
Hmmmm, you are correct....
The easting agrees, northing doesn't. There was another control point like that in their list, but neither point was ever used for anything by me. Looks like there was some pretty sloppy copying of coordinates by whoever drew the plans. Obviously a typo.
Hmmmm, you are correct....
Just to beat this dead horse some more something stinks about all this.
Here is data sheet data from a mark about a mile away
DF7937; North East Units Scale Factor Converg.
DF7937;SPC KY1Z - 1,078,820.513 1,209,190.071 MT 1.00002161 -2 00 22.2
DF7937;SPC KY1Z - 3,539,430.30 3,967,151.09 sFT 1.00002161 -2 00 22.2
DF7937;SPC KY S - 578,749.704 209,205.803 MT 0.99996255 -1 58 54.0
DF7937;SPC KY S - 1,898,781.32 686,369.37 sFT 0.99996255 -1 58 54.0
DF7937;UTM 16 - 4,096,513.258 320,466.465 MT 0.99999709 -1 12 52.1
DF7937
DF7937! - Elev Factor x Scale Factor = Combined Factor
DF7937!SPC KY1Z - 0.99998221 x 1.00002161 = 1.00000382
DF7937!SPC KY S - 0.99998221 x 0.99996255 = 0.99994476
DF7937!UTM 16 - 0.99998221 x 0.99999709 = 0.99997930
It looks like KY S coordinates alright. But the project scale for KY S at DF9737 would be 1/CSF
1.0000552
1894059.6972 x 1.0000552 = 1894164.25 (1894070.54 Plan) + 93.71
691990.1573 x 1.0000552 = 692028.36 (691994.12 Plan) + 34.24
Now here's the kicker in all this....
4 zeros in that factor, not 5 as shown on the plans. I think the answer revolves around that.
A couple of years ago the requirements for setting R/W monuments were changed in Ky. Now each monument (there were 61 on this job) is supposed to be set and a data sheet requiring Lat/Long, SPC, and PC is to be filled out and signed and stamped by the contractor's surveyor. This is on any state highway construction contract. Keep in mind, the contractor has nothing to do with setting the control, designing the project, drawing the plans, etc. Contract includes the construction and construction staking, not verifying that all the survey and design information on the plans is accurate. I've argued before that this should NOT be part of the construction contract, but should be part of the design contract, so that whoever sets the control has to sign off on it, not somebody who comes along behind them using their control. This is a prime example of why.
Now here's the kicker in all this....
I been kinda following this thread, but I don't have any constructive input...there are just too many possibilities that come to mind (most all of which have been covered above).
I will simply say (again):
I just don't understand WHY so many Highway Departments (DOTs) insist on screwing around with “modified” State Plane Coordinates to begin with. This practice made a little more sense thirty-forty years ago when the standard equipment was a theodolite and EDMI (or steel tape, or total station), and a paper field book, but TODAY, it's just INSANE in my opinion.
If State Plane Coordinates DON'T (or won't) WORK for a project, then DON'T introduce them to start with!
IF you want (or need) a “ground” system, then generate ONE, and get on with the project (one point=one coordinate).
Having TWO Coordinate “systems” associated with a given project, just BEGS for PROBLEMS (even when EVERYTHING is computed properly). To have TWO sets of coordinates that “look a lot alike” on a project is worse than insane, it borders on criminal stupidity.
Why do “they” do it? All that I can figure, is that they do it, BECAUSE “that's the way 'they' have ALWAYS done it.” SWEET! Are “they” still drafting with pen & ink on hard copy, and linen Plan & Profile Sheets? Using a Transit and steel tape? Calculating with an abacus? Driving a Model T to work?
AND NOW they want YOU to certify the Lat/Lon, SPC, and Project Coordinates on all of the ROW Monuments. OKAY fine, do just that!
Show the REAL Lat/Lon and SPC, AND the Bovine Scatalogy [DOT] SPC, and Project Coordinates, on your “Data Sheets,” along with a detailed explanation of ALL of the Bonehead ERRORS in the data that was supplied to you.
Moral of story...CHECK ALL CONTROL BEFORE doing ANYTHING!
I love these kinds of stories!
🙂
Loyal
Now here's the kicker in all this....
I hear you Loyal.
Because I work on the INSANE side I can tell you what I hear. I hear from DOT engineers that surveyors don't know how to work in state plane. Unfortunately, I hear the same from construction surveyors and I have seen them prove it in the not too distant past. I'm sure folks that pay attention to forum's like this are not a part of that group.
I've also heard that 30 - 100 ppm distortion is too high for highway design OR ROW work from both engineers and licensed surveyors. I don't believe it but hey, I've only been working with it for 25 years so what do I know? Some of us who are only going INSANE are in the process of designing LDP statewide. It was interesting bargaining with the various interests. GIS interests want 1 statewide zone. They were not happy when we advised them there are 2 zones already and we need more to lower distortion. Engineering and Surveying wanted 10ppm so the EDM will observe close to grid in a mile. This could require splitting up counties. County government screamed at that. We settled for 20 ppm and left them all kicking and screaming. Fear of the unknown and misunderstanding of scope is widespread. It doesn't seem as though the people that should get it get it.
Now here's the kicker in all this....
Since this contract was let, I believe Ky. has gone to SPC and dropped the PC business. However, I think they also decided to use the Ky. Single Zone, which is fine if you are in the Golden Triangle of Louisville, Lexington, and Frankfort, but I've been told by somebody really familiar with it that when you get way off down here in southwest Ky, or up near Cincinnati, there's a lot of distortion.
Now here's the kicker in all this....
Looks like distortion is 0.18 per 1000 ft. down on the TN state line SW of KY Lake.
It's about 0.10 per 1000 up in South Cincy. (in the 1 zone system)
Now here's the kicker in all this....
If you GOOGLE "Kentucky Single Zone" (in quotes), you will get a link to the follow PowerPoint:
The Kentucky Single Zone Coordinate Projection
transportation.ky.gov/Highway.../Kentucky%20Single%20Zone.ppt
The Kentucky Single Zone State Plane Coordinate System Bryan W. Bunch, PLS, PG
Geoprocessing Specialist III Kentucky NREPC-OIS-GIS 500 Mero Street ...
Which has lots of good stuff in it.
Loyal