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Elevations - RTK vs Levelled

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michigan-left
(@michigan-left)
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Look into the acronym "BIM".

BIM was those trainwrecks I was talking about earlier, which was at my last corporate job.

Automation and electronic deliverables is a wonderful thing, and we live in a wonderful time. 

My experience has been that most places just don't take the time to set everything up correctly, and don't get people the appropriate training.

You'd think with the $100's of thousands spent on Autodesk licensing, the achitects, engineers, and surveyors in a modern shop would integrate their packages so the workflow was how Autodesk intended.

Nope. Cut off their nose to spite their face.

Kinda odd how the last people in line (architects) are dictating how things start (surveying) and how the middle (engineering) must be changed to refelect "their vision".

If anybody thought engineers were wishy-washy, you're probably not going to like architects and BIM.

Besides, the carpenters layout most of the building stuff anyway. At least around here.

 
Posted : May 6, 2023 6:25 pm
ncsudirtman
(@ncsudirtman)
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@norman-oklahoma   hey did I miss this - where exactly in the road were the nails set? Over in that median or off on the shoulder closest to the tree canopy? 

 
Posted : May 7, 2023 3:08 am
(@murphy)
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Engineers that don't share their CAD files in 2023 are not providing a quality service. I've been working with engineers longer than is healthy for a PLS and the good PEs have nothing to hide and do everything to make sure their design is built well.  In my area, engineering colleges could do more to teach CAD, as many PEs are boarding on negligence in their thorough ignorance of modern drafting and the resulting deliverables.

I agree that hard copy plans should stand on their own merit, but a client shouldn't have to request that PE qualifications include workable CAD drawings.  I'll also add that engineers get a big enough slice of the pie that they can just go ahead and list all quantities associated with the project.  Maybe it's a NC thing, but too many firms don't provide CAD dwgs or quantities and I'm tired of spending time on Bluebeam tracing LOD and curb.  

 
Posted : May 7, 2023 3:55 am
Norman_Oklahoma
(@norman-oklahoma)
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where exactly in the road were the nails set?

In the east side curb (the right-hand side in the photo). 

 
Posted : May 7, 2023 11:13 am
Norman_Oklahoma
(@norman-oklahoma)
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BIM was those trainwrecks I was talking about earlier

You don't expect revolutionary change to happen without some pain, do you?

 
Posted : May 7, 2023 11:19 am

michigan-left
(@michigan-left)
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GIF
 
Posted : May 8, 2023 6:40 am
jaccen
(@jaccen)
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@norman-oklahoma 

Been watching it happen locally. Curb and gutter controlled by a robot, no stakes. Entire subdivisions built using machine control. One of the best things ever. Construction surveying will soon be a thing of the past. 

You're not far from it.  Some things will stick around.  I used to set up floor control in buildings so M.E.P.F's and carpenters could lay out their stuff.  Now we set up control so we can let Dusty the Robot lay out everything.  The sub's now send us their points and Dusty does it all at the same time.  The future development plans for this dude are pretty wild!

-- attachment is not available --
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"Available in the USA only."

 

You guys get all the fun toys first 🙁

 

That is slick.  I can, at this exact moment, think of 3 job sites where this thing would solve so many problems.  Even if the robot just laid things out for all the overlap issues to be visible for the subs.

 

 
Posted : May 22, 2023 7:26 pm
jflamm
(@jflamm)
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@jaccen It's definitely a beautiful thing!  I don't know how many floor penetrations I've seen overlapping the interior wall.  You can't move the wall when hotel rooms or apartments are to be built to a precise spec.  A lot of the interior stuff is kitted off-site and then assembled.  So we have to have them re-core the floor penetration.  That can get dicey if it's a post tension cable floor!

 
Posted : May 23, 2023 6:29 am
Norman_Oklahoma
(@norman-oklahoma)
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So we have to have them re-core the floor penetration.  That can get dicey if it's a post tension cable floor!

When I was doing that sort of work I had clients convinced to let me do a drone flight over their deck the afternoon before the pour. We then had a record of where the PT cables were. We could stake out new penetrations with some confidence that we would miss any cables. They seemed to find that the value in that well exceeded the cost. 

 
Posted : May 23, 2023 7:39 am
jflamm
(@jflamm)
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So we have to have them re-core the floor penetration.  That can get dicey if it's a post tension cable floor!

When I was doing that sort of work I had clients convinced to let me do a drone flight over their deck the afternoon before the pour. We then had a record of where the PT cables were. We could stake out new penetrations with some confidence that we would miss any cables. They seemed to find that the value in that well exceeded the cost. 

Woooo boy!! I don't know if I'd hang my hat on that but I'm glad it worked out!  I'll laser scan with control prior to pouring.  Put it in the 3D BIM model for our project management to look over.  They would find missing penetrations and get them installed prior to pouring. 

 

 

 
Posted : May 23, 2023 10:25 am

(@bstrand)
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I like seeing comparisons like that too.  And it seems to fall within the specs the sales guys preach-- centimeter horizontal and twice that vertical?

I'm surprised it was that good actually, I thought it might be bouncing around .03, .04, .05 even in the wide open.

Sample size is on the small side but beggars can't be choosers when it comes to free.  

 
Posted : May 23, 2023 11:06 am
Norman_Oklahoma
(@norman-oklahoma)
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I'll laser scan with control prior to pouring.

We tried the scanning approach as well but found that both the time on site and the processing time was longer. Drone orthophotos where quicker, and amply accurate.  

 
Posted : May 23, 2023 12:06 pm
ncsudirtman
(@ncsudirtman)
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I think to be honest what impresses me the most with the RTK elevations at the various points is is that Norm pointed out that the observed RTK elevations were based upon just two or more 3 second observations. I would’ve figured to get that sort of tight vertical elevations they’d have averaged at least three shots at 60seconds or more each

 
Posted : May 23, 2023 6:42 pm
(@bstrand)
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@ncsudirtman

A couple of my coworkers topo with rapid shots which I think are 1 second.  I was, and still am, a bit skeptical of the wisdom in that but so far I don't know that it has come back to haunt the company.

 
Posted : May 24, 2023 4:15 am
rover83
(@rover83)
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@ncsudirtman

A couple of my coworkers topo with rapid shots which I think are 1 second.  I was, and still am, a bit skeptical of the wisdom in that but so far I don't know that it has come back to haunt the company.

 

Rapid points are single-epoch observations with no checks beyond the instantaneous estimate of precision that the RTK engine is putting out. With a 3- or 5-second observation, if the precision tolerances are exceeded at any time the counter will reset. The solution of course converges more and gets tighter for multi-epoch shots too.

I don't have a problem with rapid for natural ground observations, but I still like to have a bit more confidence in hardscape observations.

That being said, that was my MO with older receivers running GPS+GLO at best. Nowadays, in open sky with a nearby base and full-constellation late-model receivers, I wouldn't be surprised if rapid observations approach typical topo precisions, at least enough to not make a difference in the final deliverable...but I have not tested it.

 

 
Posted : May 24, 2023 6:14 am

ncsudirtman
(@ncsudirtman)
Posts: 391
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@ncsudirtman

A couple of my coworkers topo with rapid shots which I think are 1 second.  I was, and still am, a bit skeptical of the wisdom in that but so far I don't know that it has come back to haunt the company.

 

Rapid points are single-epoch observations with no checks beyond the instantaneous estimate of precision that the RTK engine is putting out. With a 3- or 5-second observation, if the precision tolerances are exceeded at any time the counter will reset. The solution of course converges more and gets tighter for multi-epoch shots too.

I don't have a problem with rapid for natural ground observations, but I still like to have a bit more confidence in hardscape observations.

That being said, that was my MO with older receivers running GPS+GLO at best. Nowadays, in open sky with a nearby base and full-constellation late-model receivers, I wouldn't be surprised if rapid observations approach typical topo precisions, at least enough to not make a difference in the final deliverable...but I have not tested it.

 

 

agreed with both of you. I have done plenty of earthwork topos on sites after clearing & grubbing via RTK base & rover on an ATV with a rapid shot that's done by proximity to the last shot (typically a 50' spacing for flatters sites). our results have usually been comparable on the vertical within say a 0.15' tolerance but we also have to keep in mind that the clearing/grubbing activities remove the root mat and also tend to consolidate the looser sandy/silty materials on site so the ex topo will usually lower some due to the equipment compacting it or shifting it around

 

but to see shots that tight vertically with only a couple of 3 second/epoch observations averaged together is very impressive for me. Has me itching to try it with my BRX7 if I can ever get the chance to demo a base & purchase it. thing I'll still stake any gravity utilities that are flat or curb line conventionally with the robot though lol - eating a few manholes & 48" RCP being laid wrong just isn't worth it

 

I have seen where some contractors are self staking with RTK GNSS in other states where grades are exceptionally flat and I've wondered how the as-builts turn out...

 

 
Posted : May 24, 2023 6:35 am
MightyMoe
(@mightymoe)
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We've done extensive testing for rapid shots and continuous topo shots both RTK and PPK. For me the only problem encountered were during the very early days when bad fixes for long periods were an issue. Since then, I've haven't seen any issue with those types of "ground" topo survey. Far, far, far better than any other option. Better than even the big boy Lidar surveys. These surveys were done for mining, oil and gas, reservoirs, dirt design.

If the topo is for detail street, building design, then TS topos are needed. 

Using the correct tool for the job, but topo with GPS is a game changer. Fast, efficient and accurate. 

The main concern when doing them, especially PPK surveys is to keep the fix for long periods. Of the three PPK seems to be the most accurate, but it's a small difference. My suggestion as always is test it. Go out in the parking lot, mark points and see what you get. That's one of our testing techniques. When you're doing a bigger survey go back and re-shoot points randomly. That should be part of the survey anyway, new HIs, same point. 

 
Posted : May 24, 2023 7:15 am
(@i-ben-havin)
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@va-ls-2867

Just asking for a friend...

(Many apologies for hijacking this thread)

When observing 20+ satellites (GPS/GLONASS/Galileo/BeiDou), and with so much correction data having to be moved, does base to rover correction data transmission via radio experience less latency than on-site base to rover correction data transmission via the internet?

 
Posted : May 24, 2023 8:04 am
(@va-ls-2867)
Posts: 514
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@i-ben-havin yes, there is a delay in receiving the internet stream.

 
Posted : May 24, 2023 8:30 am
Norman_Oklahoma
(@norman-oklahoma)
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Topic starter
 

I don't have a problem with rapid for natural ground observations, but I still like to have a bit more confidence in hardscape observations.

I share your preference. But the vendors all insist that even an "instantaneous" result is the product of many independent solutions. 

 
Posted : May 24, 2023 9:45 am

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