I am new to RTK but not new to construction surveying. The job is a complicated mess, the contract requires a licensed surveyor be involved with field work and at they want stamped as-built plans.
The original pipe was located with metal detectors and a stake was set. Then a survey company located those stakes, they also set the control points that are on the plan. The job is 6 miles long, it has been discovered the original pipe is off in a few spots 1'-10' of where the survey company located it. My company hired a survey company to perform the layout and topo shots of the new pipe as its being set. I was hired by the contractor to take over the job from the surveying company, all the field work was being performed by a PLS that works for the company. I worked with him for a week, during that time he told me when he first came on the job he set up on a bound and sighted a plan control point and had .150 HDE and .130 VDE he then said he felt that was good and started working off those points setting new control as he worked. He also located the original pipe in the areas that were off from original survey. He set up on the plan control points and located the pipe. The plan control points havent been checked if they agree as a whole.
When I started I was not happy with the control points and the way he had been setting them.(using range pole for the FS shooting it after the gun has been set up all day on construction site and using the wrong prism settings for Leica). I went to the begining using 2 plan control points had .006 HDE and .008 VDE. I then ran the traverse 3,000' and located 2 other plan control points. Those 2 points were off .150' and different directions. The licensed surveyor found 1 of the original control points to be out 10.5'.
I sent an email to my bosses saying theres a problem. I said I'd like to run traverse begining to end checking plan control and the existing pipe, and set points outside of working area. But they dont understand but they think they do. I was also told the other guy in licensed and I am not and maybe I'm trying to be too accurate. The pipe does land on existing culverts and crosses roads with lots of utilities.
Now I am working off my traverse, I am 5,000' from where I started and all the plan control has been wiped put due to construction. I do mot have the time to run traverse, I have to be set up while pipe is being laid. This is why I would like to use RTK to check, adjust, or set new control. I think if I'm within .200' I can make it work.
Like I said, a mess!!!
I am not even 40% sure how those plan control points came to be. They are on the plans with coordinates. I can only guess they were set with RTK and not very well. The original survey was done by a company hired by the designer. I do not have access to any information relating to original survey.
Just seems to me that if you don't get a handle on the over all big picture of the control situation, you might be setting yourself up for some nasty surprises. You can accomplish that doing either static or RTK. My personal preference is for static but redundant RTK will do the job.
If you've ever tried to frame a complicated roof on a house that is not square and plumb, you'll have an idea of what a nightmare gobbed up control can be.
A powwow with the designer might be in order.
Not all RTK is created equal. Our local RTN can't get within 0.2 in some places. Our base rover will get .02 3D if procedures are followed and conditions are good. It is worth noting his comment of 'without a base'...
There are many variables here. With RTK and any GPS the amount error can point to the type of error.
Are you on State Plane Projection or assumed coordinates?
What is your average elevation?
You mentioned 1.5ft difference in EDM Traverse vs. Original Survey for the 3000ft traverse. This sounds like error in your EDM traverse. How many angles/distances SETS per turn? Sounds like angle error. What was angle closure? Are you reducing ground to grid distances?
Then you mentioned 0.20ft difference in RTK vs Original Survey. Are you on State Plane Projection in your controller, or using a localization/calibration?
Are you using GNSS (NAVSTAR + GLONASS) system?
Is your base on a stable point? have you checked the vials on Base and Rover setups?
How are checks on points closer to the base?
You can use RTK to check the control. I would use State Plane Coordinates, never a localization. I suggest locating all points from two different base points, plus measure each base point with RTK. This way you have a closed triangle to each point. Then you can run it through a Least Squares to further adjust. As others have suggested, you can also include OPUS and OPUS-RS checks. But most construction GPS people do NOT have that option.
Lee Green
sounds like an explosion waiting to happen, for sure.
If he has post processing ability, I agree that OPUS would be the way to go. I think a lot of people buy RTK gear without that ability though. I know I had to pay extra for it when I bought my Topcon Hiper Pros.
Do you have the ability to post process data?? If so, you could collect at the base station as you tie things down then send the files through OPUS.
Other than that, it sounds like you are trying to herd cats.
What are you using for the RTK and what are you using for software?
I use Topcons. I can export the RTK vectors out and import them into SurvNet (Carlson). Multiple observations with different constellations can provide some very good results. If you are using a different GPS unit and if you cant export the RTK vector data and if you use Carlson, send them a file and they will update SurvNet.
I would suggest static locations if you have the equipment.
Is the project coordinate system outside the usual limits for that system? We once performed a survey in a UTM zone that the client requested, even though we were really in another zone. This caused a lot of "stretch", so that the ground distances wouldn't match the control point coordinate inverses, by a lot. It was something like 0.1' per 100 linear feet.
I have Carlson Survey OEM 2015, I am considering asking the boss if I can buy Star*Net. I am using a Topcon GR-5 base and rover with a Topcon Tesla with Pocket 3D. They bought it before I started. When I was hired I was able to pick what I wanted for a robot. I picked Leica TS-15 3" with Leica CS15 loaded with SurvCE. I am wondering if I can use the CS15 with SurvCE to run the Topcon RTK.
My 3,000' traverse has 9 turns, all doubled, and used legs with prism for BS/FS. The 2 original control points that had the .150' error were 400' from eachother. Unfortunately I do not have the time to close the traverse properly. I was lucky to run the 3,000' because they canceled laying pipe due to the rain, (The prisms were wiped before each shot). I know if/when something does go wrong it will automatically be my fault because I'm not licensed, and the other guy is.
Going to the designer would be waste of time, their solution to the error of original pipe is to have the surveyor locate it. Then send the new locations to pipe manufacture and then calculate the new location using pipe laying schedule and adjust it to follow the original pipe. Which the licensed surveyor somehow calculated the pipe in a snake shape. I now have the responsibility of calculating new pipe location.
The licensed surveyor also has his data collector set to KY North, and the drawing he sent me was set as AL East. I asked him why he hasn't changed it and he just shrugged.
I am in state plane coordinate system
Mr. Stoner,
"The licensed surveyor also has his data collector set to KY North, and the drawing he sent me was set as AL East."
OK, I remember your other thread now. So this is THAT project?
Dave
Yes it is the same project. I have had problems before with boundary surveyors thinking .08' backsight check was close enough to lay out anchor bolts for building construction. Not sure if this licensed surveyor doesnt know any better or just doesnt care. Whatever it is he has causeed a mess.
by stoner1826 @, Thursday, November 13, 2014, 21:17
"I ran a traverse 3,000' between 3 original points, two were off 1.5' in different directions."
by stoner1826 @, Friday, November 14, 2014, 08:29
" I then ran the traverse 3,000' and located 2 other plan control points. Those 2 points were off .150' and different directions."
"The licensed surveyor found 1 of the original control points to be out 10.5'.":-S
Oops. The error I found when I traversed was .15' The other surveyor recently ran traverse between a few of the plan control points and found 1 to be off 10.5'
As of now, I have a traverse that is 4,500'. I measured 4 of my points with RTK 3 times throughout the day. All the shots were within .03' I averaged those shots and have a consistant .200' in my traverse points. I am not to sure what to do now moving forward.
I'm curious what the accuracy specs are for the project.
I don't know anything about pipeline surveying, but I thought you were talking 1.5 feet (assuming the 10.5 was a blunder) ...
Huge difference to 0.15'. Is it great? No. But how close is this even built?
How are the results of your RTK observations matching with the published coordinates?
With the RTK I am hitting the plan points around .01-.03. The pipe location is only crucial at road crossings and where it sits on existing culverts.
> I am working on a water main pipe line project that has started a few months ago. The survey work has been done by a survey company, and not done very well. I now know the original traverse was set with GPS and not very well. I ran a traverse 3,000' between 3 original points, two were off 1.5' in different directions. There are only a few original points left due to construction. I am currently doing all the stake out, topo shots with a robot. Unfortunately I do not have time to run a traverse six miles and close it. I do have a RTK, and shot the last two points of my open traverse and I am .200'
>
> I am wondering what is the best way to set control with the RTK if at all. I have seen few posts about shooting points multiple times throughout the day initializing each time and then average them to create one point. I was also thinking of doing a resection using the averaged points.
>
> Thanks for any help
Is this a poll?
I vote for a pair at the beginning, and a pair at the end, and a pair in the middle.
Shoot them again after a half hour wait.
Traverse through each.
Scale your traverse appropriately, to bring it to grid distances (since that is likely what you obtained from RTK).
Rotate on the first backsight (RTK derived point) to hold the bearing to the last foresite (RTK derived point) at the end of the project.
Now you have something to compare...
It is a mistake to use a pair at the beginning and expect to precisely match a pair at the end of a long route traverse, no matter where you get the starting pair from. If you are off 3 seconds on your initial backsight, and traverse 10000', you will miss by 0.15' even if everything else is perfect. Analyze and reduce your raw data correctly before assuming anything.
