Just wondering if anyone has suggestions for as-built surveys of pipelines. I'm currently on a project that contains 3 pipelines (16", 12", 6" pipes) for a stretch of about 15 miles. The ditch trench is 10ft deep (about 16 ft wide), and we are not allowed within the ditch due to safety concerns. Previously, we used an R10 attached to a 10ft pogo, and reaching above the pipes with a 14ft painters rod, holding said rod on edge of the trench. This method was extremely difficult and could only be done by someone tall and very strong. When the project starts up again within the week, we have been told by our company to NOT use the r10 as this method was very unsafe. I am going to be trying a reflector less total station, but I have also heard that Trimble recommends using a distometer. Has anyone used these techniques recently and could suggest or advise me? We are using the Trimble TSC3, with their pipeline module. 

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What about using a drone? You would be able to set control points along the top of the trench and outside the active construction zone.

This has  been brought up, but we need to verify that cover (2.4m) will be good at every weld. Hence, we need this data in real time, with the construction backfill beginning right after we approve it after survey. This gives us about an hour to observe all welds and sign off on paperwork, and have limited data/internet availability for pot-processing.

By working your way up the line, performing as-built at each weld. Conformg cover .They can be backfilling behind you. 

Alyssa,

Knowing the time constrants for the data needed Drones are definitely out. We use a Trimble S6 Robot and have used the reflectorless mode when locating stripping along the Intersate for our DOT jobs. I will say they are accurate. The Engineer in charge of these projects is annal about the horiz. and vert. accuracy of the shots. So when we first got the robot, we shot the points in reflectorless mode then we had to shot them with a level every so often to prove the Robot was doing it's job. So you should be able to collect the data needed in this manner.

I know how i'm gonna shoot my striping the next time. The last 4 lane with decel lanes scared me even with a spotter and flag waving.  We were trying to time the stoplights and I felt endangered even with the speed of the GPS. Reflectorless has been a game changer for me.

We do this work every day. The way you were doing it should have been ok and thats the way I would have been doing it- even walking along the pipes as there were people in that trench before you came along. 

However- if thats not possible you can use reflectorless- you don't need a disto- the pointer on the disto will be too hard to see in any case. 

Can i suggest that you set a series of station points along the bank with your GPS- as far apart as possible- but within line of sight. Then using your total station just work your way along the bank- shooting points of detail onto the pipe.  it will be much slower than just using your GPS but hey- the powers that be never make a surveyors life easy do they?

Youre right for sure! All this safety nonsense, but yet they want the job done quickly, makes for a difficult situation. We would have continued doing it the way we had been for the past couple months, but I was working as an assistant, and my chief was able to do all the heavy lifting. He has since moved jobs, and I will be in charge (with another woman as my assistant) this option is highly unlikely, since neither of us can fill in for the 6', 200 lb guy in charge of the rod prior. I tried to lift it, and that guy made it look so easy! And with this being my first project as party chief, I'm trying to prepare myself the best I can

That being said, I believe we are trying the reflectorless. I know this will be a learning process, and a lot slower with the set up of the station, but I think its our only real option. I mean, at least we get paid by the hour! Thanks for the words of wisdom!

I encountered a similar situation when surveying a creek / drain bed. We set up a series of RTK stations the bank, one where the as built shots where to be taken and another at sufficient distance to enable a reliable backsight bearing. If required a 3rd point could be used to confirm the bearings.  From these 3 stations, you will have position via RTK and a bearing. 

A total station was then setup and reflected shots taken. Considering the station was within metres of the creek/ drain, the reliability of the measurements would be sound.  You could also use a prism to obtain surface levels of either side. A quick tape down the side of the trench for a rough check 

Considering the project is over 15 miles, accuracy would be relevant to each cross section not from start to end

I hope this helps.  Tim

Thank you! We will be trying everything we can, and the first couple days will be a huge learning curve for me. But knowing that someone successfully used it makes me feel a little better!

The Trimble S6 Robot has proven to be very accurate when I use the reflectorless setting.  I mainly survey roof peaks for solar installation using this method.  I'm not sure what your tolerances are but i can't imagine that it wouldn't be accurate enough for an as-built of a pressurized pipeline.

If you are going to use a Trimble for the reflectorless i would recommend using the tracking mode rather then the standard measurement mode as i have found it to be more accurate with the S6 that i use. Although the tracking is a single observation you can move the cross hairs around to see what distance range you are measuring to surrounding objects like trench wall, floor and the pipes and ensure that you are measuring what you want to measure and not an object behind. I found that the standard mode would seem to do some sort of averaging at times between the objects that were within the footprint of the reflector less beam and you would end up with short building walls that were out of square by 100+mm. Its just easier to see the raw distances as you go.

What about a man on each side of the trench, each holding an end of a light-weight rope with a 360 prism secured to the center of the rope. Another rope, or small fierglass rod could be suspended from the rope/prism to the pipe so distance to the pipe could be measured accurately. Simply walk down the sides atop of the trench stopping to take shots where necessary.  

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