So, if you were in the other surveyor's role, it wouldn't occur to you that the easiest approach to verifying the project control is to determine the NAD83 coordinates of the control points and compute the transformation that relates them to the Epoch 1993.0 coordinates that your office generated?
My office didn't generate any coordinates, and that didn't occur to him. He didn't do that. If he did he wouldn't have had an issue with the control.
So what's your point? If all the 40 control points, 4 HARN monuments, 68 ROW monuments get destroyed 100 years from now we could go back and somehow use a future 15 times later adjustment from OPUS to replace these monuments, not tie them to the given monuments?
And even though my contract didn't ask for it nor did the construction surveyors ask for it, I should spend time giving the DOT some transformation that they don't want? And won't use and won't keep and will probably file in the circular file if I send it to them? Why exactly would I do that?
I'm kind of surprised at the confusion
Shocked might be a better word, but me thinks they are just shining us on to keep the discussion going, 😉
>
> Shocked might be a better word, but me thinks they are just shining us on to keep the discussion going, 😉
I'm not so sure....:-|
[sarcasm]on another note, think how far off "your" project control would be if it had been local 50000,50000, 1000 at the 1st horizontal control point....[/sarcasm]
Of course you may be right, and maybe you run into this stuff all the time. But you did say the construction company got the contract, and then the construction company retained a surveyor. Isn't it possible the construction company does not know the difference and their contract with the surveyor they hired mistated things, and/or did not supply the documents for review before bid?
Nope, not possible, this information isn't only handed out, but is on file at the county courthouse. You can't miss it. He couldn't have gotten the control without the spreadsheets.
> So, if you were in the other surveyor's role, it wouldn't occur to you that the easiest approach to verifying the project control is to determine the NAD83 coordinates of the control points and compute the transformation that relates them to the Epoch 1993.0 coordinates that your office generated?
>
> My office didn't generate any coordinates, and that didn't occur to him. He didn't do that. If he did he wouldn't have had an issue with the control.
>
> So what's your point? If all the 40 control points, 4 HARN monuments, 68 ROW monuments get destroyed 100 years from now we could go back and somehow use a future 15 times later adjustment from OPUS to replace these monuments, not tie them to the given monuments?
No, the point is that if you're checking the control monuments by a combination of GPS and conventional methods, you begin with the best quality ellipsoid heights and NAD83 positions available and use those to determine (a) what sort of transformation will be required to transform NAD83 (2011) Epoch 2010.0 to what is essentially a project datum.
For machine control issues, I'd think that having accurate ellipsoid heights to compare to leveled elevations would be just as essential as verifying that the project control was free of any systematic bias (rotation or tilt) or distortion.
Probably the red flag would have been when I hit the job and found that none of the monuments had punch marks on them. :>
Seriously, you think they aren't understanding this? Can't be, I just won't believe it!!! 😉
But if they don't.........OMG
MM,
I'm not the least bit "confused," but I'd honestly like to know what you have against OPUS. OPUS solutions are longer-duration observations than fast static, and CORS stations are generally tighter than the average base setup.
Point 2: Aren't surveyors supposed to talk amongst themselves and help each other out? What's wrong with a friendly phone call?
Point 3: Except for shifting tectonic plates or perhaps Texas mud, hubs don't usually move. If two surveyors disagree in their measurement of coordinates, I'd want to talk about measurement methods and coordinate systems, quietly asking and answering in turn, instead of hurling insults.
Dave
I'm not the least bit "confused," but I'd honestly like to know what you have against OPUS. OPUS solutions are longer-duration observations than fast static, and CORS stations are generally tighter than the average base setup.
Point 2: Aren't surveyors supposed to talk amongst themselves and help each other out? What's wrong with a friendly phone call?
Point 3: Except for shifting tectonic plates or perhaps Texas mud, hubs don't usually move. If two surveyors disagree in their measurement of coordinates, I'd want to talk about measurement methods and coordinate systems, quietly asking and answering in turn, instead of hurling insults.
My point is that OPUS is great for what's it's used for. No problem with it. But use it correctly don't puke out OPUS numbers over the top of already established control that wasn't done with OPUS, follow the footsteps of the control surveyor just like you would of the boundary surveyor. This is basic and all the control was given out. OPUS didn't exist at the time the control was run, and neither did CORS so they aren't useful.
> I'm kind of surprised at the confusion. There are numerous flavors of NAD83 even through the history of OPUS. Those various realizations vary. HARN derived coordinates determined in 1993 from a young CORS network will not precisely match OPUS derived coordinates in 2013.
I think you're missing the point of checking project control before you start staking away. Would a surveyor want to know if the whole project coordinate system is rotated out of whack before he or she simply assumes that it's oriented Grid North as claimed? What about systematic scale errors? Would a surveyor want to know if the scale of the whole control network shows some systematic error? Would it matter if the ellipsoid heights of the project control points show some significant tilt?
Or should a surveyor just set up and start staking away?
MM,
What am I missing? Help me to understand.
"This guy went out and declared all the control unusable, the control we just got done checking which was all good."
What do you mean by "good?" Do you mean that your control tied well to the HARN points and DOT monuments? All your distances and angles checked OK? Your map overlays the proposed site and easements well?
"...this guy went out and started to run static OPUS on it and it didn't match."
"...guy says we need to make it match..."
Didn't match WHAT? WGS84 Coordinates, map projection, distances, rotation, scale, angles? If I was going to lay out a highway, the first thing I'd do is check to see if our control matched. If he can't calibrate to your numbers, he damn sure oughta mention it.
And let's assume, for the sake of argument, that the fellow was desperate for work and is in over his head. (Like nobody here has ever been in that position.) Wouldn't it be a kindness to call him and tell him why his OPUS solution is inapplicable to the situation at hand?
Dave
It's as though you don't read beyond the first paragraph. What part of relative tolerance and relative accuracy, which I already mentioned, escapes you?
Not using project control is just asking for problems, especially after design. Even if the original surveyor set a BM on a bridge abutment and assumed an elevation of 100'. Design used his datum and if you're the lay out guy, you have to honor it too... or get a new job.
I've seen this kind of BS several times before. Once a lay out crew brought in control from a completely different adjoining job that was based off of some other control and blew off the existing project control. Then they started to complain about how nothing would fit and how wonderful their control was on the other project. I'm sure it was...for that OTHER project. Do again... like Moe says, it's not that difficult.
I know of a site that has seven different coordinate systems that had been used for years. Before GPS. It was common to assume coords and go with it. Throughout the years, they added on to it...and added onto it again...and again... 10 years later, different engineer, new project over here in the corner, new assumed project control, etc. Sounds like this guy would have a coronary if he had to do lay out there.
> It's as though you don't read beyond the first paragraph. What part of relative tolerance and relative accuracy, which I already mentioned, escapes you?
No, I read your post and noted that you were neglecting to recognize that if you're using GPS methods to do the verification survey you need ellipsoid heights and NAD83(2011) positions of known accuracy to use in computing your GPS network. OPUS is a natural first step.
On a large project, several OPUS-derived positions are natural to add to the network for adjustment and those might immediately show problems with the control monuments other than a constant offset.
The control for this highway was first laid out in the 70's. It was of course done with instruments and distance meters. Then GPS came along in the late 80 and the DOT began running control with it. Ashtec receivers with these big cables. That was done in NAD83/86. If you had one of the older projects given to you like the one i did in the mid 90's then you needed to survey in NAD27 using the control monuments provided even though 83/93 was available. There was quite a shift in 93 when the network was updated from 86 to 93. About 2' here and DOT updated to it. I never actually saw a 83/86 project, but there probably were some. Once they went to 93 they decided to stick with it even though there have been updates since. They always tied to HARN and for this highway laid it all out that way. So for more than 100 miles there are intervisible control monuments every 1500' or less. So over the years they upgrade 10 mile sections of this highway using control long established. Each 10 mile section gets its own scale factor and they give you a sheet with the info you need to do the work. Simple really. Just set up a projection file in trimble, occupy the control and check the points along the highway. They were already static occupied and adjusted. The road was flown, targets laid out, utilities located, bridges and culverts surveyed, property corners and row monuments established. Row maps were drawn and filed. Engineers designed the road and construction plans issued. Now comes a guy declaring the control "off" because some OPUS solution doesn't match the lat longs he was given? Of course it won't. And it was leveled to local bench marks and that won't match either. You need to survey in the system given too you and that will work. DOT is well aware of OPUS and understand these issues as well as anyone i can think of. They have been GPSing from the beginning and running more static control than anyone else. And no im not calling the guy. Im sure DOT will take care of that. The odd thing is why anyone would survey that way? What is the mind set? Where would it come from?
I am fairly new to GPS. It seems to me, if I were that other surveyor, I would have uploaded all the given coordinates first, and then occupied a number of the control points to verify that my GPS system was confirming and verifying an existing coordinate system. I probably would have collected several OPUS values on several points for comparisons sake, but the project coordinate system has already been established. I must follow suit. OPUS would be just for me for future reference and to tie the derived coordinate system in to OPUS values.
The other surveyor should not have declared the coordinate system wrong. In reality, he did not know how to get onto an existing coordinate system. Wasn't that the whole point of this thread? :'(
What are you talking about? You arent making any sense! Shawn is completle on topic!
For god's sake yes it was. This has become so weird its almost insane stuff.:-(
told ya-:-/
A Route Survey, for how many miles? How were the corrections handled along the route or was one correction used for the whole length? Don't think there is enough info to determine who was making some bad assumptions. Original control before the days of low distortion projections, we all know why Hwy Dept's. are starting to use them.
jud
Lol. Unfreaking believable:'(
