Andy
They are dismissing it, it's just very upsetting that they would have to deal with it. After going to all the trouble to lay out, drive down the rods, pour concrete around them, spent all the time and effort to static control them, run levels the entire length and back, do the adjustments, produce the control sheets, map the job, hand survey voids, bridges, culverts, utilities, hire a company to do ROW maps, and check the control horizontally, do the designs, acquire new construction easements, design the new construction, produce construction drawings, bid the job and let the contract a guy comes along and declares all the control wrong because the cult of OPUS says so.........
Yes, yes they are, the control is done using state plane grid coordinates and the work for design and construction, ROW is done using surface coordinates based on the state plane grid coordinates multiplied to get them to a surface plane. You can check the control using state plane values if you wish but all work is to be done in surface coordinates for construction and layout. Simple. Easy. Surveyors work with it all the time!!
Kent...
Yes, if the client is stating that the control is good to go, you must respect that ....in writing of course and signed off by each party of interest. But I always feel that it is an obligation to check that control for the client's benefit.
Yes check the control, don't redo it!!
It checks, not only this project, but it checks to the project to the east and to the west, we also tied into both of those. Different scale factors but no big deal. Basic surveying 101.
I found it...
>DOT sends out control spread sheets with: state plane coordinates, surface coordinates, ellipsoid heights, geoid heights, latitudes, longitudes, the state plane zone and that its NAD83 and in this case 1993 EPOCH, included is the combined adjustment factor and how it should be applied.
So how are the surface coordinates derived?
Multiply each grid coordinate by their CF?
It's disturbing that some surveyors don't know that OPUS won't match old DOT HARN values.
Yes, each coordinate gets multiplied by the scale factor. DOTs pretty much everywhere do this. In this case about 1.0003 or 3' each 10000'
I will say least squares and site calibrations can make excrement look really good.
However, if the DOT is taking responsibility for the control then use it with their values.
If I was staking with RTK I would be inclined to convert the design to grid, set the base over a control point using the DOT N,E,Elev and a Geoid model, check a bunch of other control points and stake away. True there is a systematic error in GPS if you aren't using ITRF coordinates but the DOT grid coordinates should be close enough to ITRF so that the difference is negligible. If give your base the DOT ground coordinate then it could start to matter. I guess most do a site calibration but that can be dangerous.
Total station, just use the ground coordinates.
What we have hee-yah....
> Sorry, felt like Kent for a minute there... It's hard to understand why this is so hard to understand.
I have said here before that most surveyors do not understand datum issues beyond what their salesman taught them, and do not think it desirable to do so. The people who participate on this board are above average.
I know that Kent understands control and datum issues better than most - probably better than I do. I just think that there has been a disconnect in communication. After all, this has more to do with project management than it does with technical issues.
What we have hee-yah....
> So the staking surveyor is obligated to ensure that the control he is using is correct relative to other control in the network - in the manner of ensuring that he has found the right monuments and they have not been molested - but not to rerun the entire network, nor to quibble over reasonable residuals. If, in so doing, he should find some significant irregularity, his obligation would be to alert project management and initiate a resolution before proceeding.
Exactly, and the smartest time to check for irregularity on the control network to be used for project layout is *before* the layout and before there are large machines waiting on surveyors.
> Checking control before use is completely appropriate. Running an OPUS and declaring a network invalid based on a raw comparison is not.
I take it that you aren't disputing the idea that two or more OPUS solutions can spot major errors in a control network, which was the point. That is, you can check even a bastardized control network such as is the subject of this thread by NAD83(2011)Epoch 2010.0 coordinates if you're interested in checking orientation and scale of the network.
> > So, considering that the control points you'll be setting up on will probably get destroyed in the course of construction, how are you going to document what you laid out if you don't have a check survey that shows what the coordinates of the control points were as provided to you?
> >
> > I'm a land surveyor and I thought that contractors were actually concerned about these sorts of issues that can really bit a contractor in the wallet.
>
>
> 1. It's highly unlikely that 10 miles of control will be destroyed.
>
> 2. All projects I've worked on the surveyor had the wisdom to put control outside the Limits Of Work, we clearly stake and flag them (the CPs) and threaten bodily harm to anyone who disturbs them. (So yes, we are really concerned)
>
> 3. In the 'unlikely' event that so much control is wiped out that it needs to be re-established, well ........ that's when I call my surveyor back in.
And that's exactly the point. If the control network was jacked and had distortions, you won't be able to re-establish control points from more distant parts of the network unless you have a record of where the missing control points really were (as opposed to their declared project coordinates that have only an approximate relation to the real world).
From a construction standpoint, the time to do the checking of control is before there is a whole jobsite crawling with people and machines waiting for an answer.
> Yes, each coordinate gets multiplied by the scale factor. DOTs pretty much everywhere do this. In this case about 1.0003 or 3' each 10000'
If it's like Oregon was prior to 2011 each point gets multiplied by a project average CSF, rather than the CSF computed at each point. StarNet will output either way you prefer.
Oregon now has LDP projections and is moving away from this procedure.
This is how I do it with Trimble.
I set up the data collector file to the state plane zone and apply a local site setting which simply multiplies the coordinates by the given scale around any coordinate you input, in this case I will input 0,0. I apply a Geoid to the file in this case it is Geoid09. Then I import the N,E,Elev file of the surface coordinates. Then compare the LAT, Long of the points to the given data from DOT. They will show a difference on some at the 5th decimal point in DMS format, but no worries there.
Now you have a file with the correct Lat, Longs for the points and N,E of the surface coordinates. Also, you have calculated an ellipsoid height from the leveled elevation numbers and if the geoid is good in the area it will give you the best elevations you can get with GPS. A calibration is fraught with errors particularly along a 10 mile fairly straight highway. Then I go out and set on primary control with my base and start checking the existing control monuments which is what they want me to do.
If I'm doing the construction staking, after checking the points I will have a crew run levels along the length to check the elevations which are the numbers I want to be the best on a construction project. If I see any horizontal out more than 0.05' I will look at it again, and anything out more than 0.02' vertically will get another look and maybe a new elevation.
What we have hee-yah....
I have a deep and abiding respect for Kent's knowledge. I have an equally deep and abiding disgust for his intentional obfuscation of other's thoughts as communicated in plain text. The arrogant condescension that generally accompanies his efforts is simply an added bonus.
If you doubt what I'm saying, look no further than the comment below in which Kent continues to perpetuate the inaccurate perspective that this is somehow related to using OPUS to divine the mystic properties of an elusive, bastardized State Plane Coordinate System, which is clearly contrary to OP's scenario. But it makes for good sport to misrepresent the situation and then skewer the recreation.
> If I was staking with RTK I would be inclined to convert the design to grid, set the base over a control point using the DOT N,E,Elev and a Geoid model, check a bunch of other control points and stake away.
Yes, and presumably you'd check the project control in advance of actually needing to stake anything from it. So, what gets that done the easiest?
> True there is a systematic error in GPS if you aren't using ITRF coordinates but the DOT grid coordinates should be close enough to ITRF so that the difference is negligible. If give your base the DOT ground coordinate then it could start to matter.
Yes, and presumably the bastardized project coordinates differ quite a bit from NAD83 SPCS coordinates.
> I guess most do a site calibration but that can be dangerous.
In particular for the vertical. I'd think you'd definitely want to use a geoid and, if necessary, several co-geoids for different parts of the project to match leveled heights.
> Total station, just use the ground coordinates.
Although you still have to check the control network in advance of staking and GPS remains the best way to do that.
If it's like Oregon was prior to 2011 each point gets multiplied by a project average CSF, rather than the CSF computed at each point. StarNet will output either way you prefer.
Oregon now has LDP projections and is moving away from this procedure.
Yes, exactly the same, a state plane coordinate of 10,000, 10,000 with a project scale factor of 1.0003 becomes 10,003, 10,003. The scale factor is the same for the entire site.
I do like LDPs but if a surveyor can't survey in this simple surface coordinate system how in the heck will he figure out an LDP?
The OUPS/state plane cult will rebel.
So new control was laid out two years ago in an LDP, funding as it is delays the project for twenty years and OPUS has new numbers NAD83/2030, and a new geoid has been issued. A surveyor goes to the field and says the control is wrong because it's .20 and .5' "off" the new OPUS numbers and everything needs to be "fixed".
> > > Are the NAD83 1993 coordinates grid?
> >
> > No, MM posted that they are bastardized DOT coordinates that have been scaled, apparently still resembling SPCS values.
>
> Your reading comprehension is hilariously frustrating or frustratingly hilarious.
Not really. Are you thinking that the actual construction plans don't have bastardized coordinates on them?
:good:
The original surveyor laid out a control network, and hopefully provided enough of the "metadata" in his published network drawing. All the the right-of-way work and highway design is based off of that network data. If you are then tasked to stake said construction, you make sure you can check to the network provided and stake it to the coordinates the design was done off of. This is not a geodetic problem, it is using local coordinates to do your work in to be in the same datum as the design and topography was based on. If it does not match "OPUS" then you might let the original surveyor know, but it would be best to use the same coordinate datum that all of the right-of-way legal descriptions, topography, and design work was based on.
If there is a problem with the "relative" coordinates, (Ie the "Measured" angles between existing monuments or the measured distances, is off a lot, then you need to go through some new and possibly extensive gyrations.)
Or am I misunderstanding the problem?
> And that's exactly the point. If the control network was jacked and had distortions, you won't be able to re-establish control points from more distant parts of the network...
But this really misses the issue here. Which is one of a "surveyor" comparing a NAD83(2011) OPUS to a "modified state plane" based on an extensive NAD83(93) local network and declaring the network unusable on that evidence alone.
> Are you thinking that the actual construction plans don't have bastardized coordinates on them?
So what if they do, Kent? Have the operations of division and multiplication become too complex? The control, according to the OP, provides State Plane Coordinates and surface, pseudo, modified, bastardized State Plane Coordinates scaled with a published scale factor from 0,0. If the construction plans are based on this scaled system, it's fairly simple to apply the scale factor to them and obtain true SPC values, based on the published reference frame - which in this case, as has been painfully made clear, is NAD83, 1993. Or, if the software supports it, creating a modified system with the published scale factor that natively works with the scaled system. OPUS is entirely unnecessary for any of this as it is also entirely unnecessary to compute the relative positional accuracy of points in the control network.
If there is a problem with the "relative" coordinates, (Ie the "Measured" angles between existing monuments or the measured distances, is off a lot, then you need to go through some new and possibly extensive gyrations.)
Or am I misunderstanding the problem?
No you understand, I've worked on dozens of these projects and I think maybe found just a handful of points I had a problem with, usually I'm doing legal work so I'm uninterested in elevations beyond their requirements for property corner elevations which are not very tight, but it's rare to see issues with their control.
