Another firm on a major high profile urban multi-mile project did not set control points. They simply referenced to 83/95 NAD & 88 NAVD using a networked GPS & OPUS solutions. NGS monuments found within or near the project corridor were not referenced on the plans. No statement of accuracy is found on the plans, so we have no way of knowing if any redundancy was used in establishing coordinates. Right of way and easements are being acquire using their plans. No they did not reference a project epoch.;-) The projects will be let to bid to contractors in several multi-mile segments. Does anybody besides me think that we will see some drama during construction? Has anyone seen this procedure for this type of project? GPS is a great tool for establishing project control and collecting data. When did it become project control?
Should never have been project control. I'm with you, the sparks will fly down the road......
No, not a good situation for sure, years can pass from highway control to construction, even decades, control monuments are necessary, and once set they need to be considered fixed and control everything. Hence the name control;-)
A "no control" scenario would eliminate the kind of epic "debate" you and another poster had a while back.;-) The debate had something to do with control monuments and OPUS.
Sounds like a good opportunity for speed bumps and jogs at the beginning and end of the multi-mile segements.;-)
A "no control" scenario would eliminate the kind of epic "debate" you and another poster had a while back.;-) The debate had something to do with control monuments and OPUS.
OOOOOhhhhhhhhhh nnnnnnnnnnnnnoooooooooo not again!!!!!!!!!!!!+o(
NGS gave a presentation at the New York Conference a few years ago where they said something along the lines of that they consider the proper way to tie into NAVD88 to be via GPS. They also made statements about GPS being the primary way to tie into the new datums coming out...not ground control.
If you have sufficient CORS around, that might be considered your primary control. If they did their work right and tied into those CORS stations you should be able to re-establish with good results. I would field check the heck out of it, but I would be you'll be pretty darn close.
That said it is required by NYSDOT and their contractors to have primary ground control (azimuth pairs) every two miles max. And thats what I do.
Tom
well, that will work great when you have to blue top with a level or robot, wait guys, I'll set some nails static them four 4 hours, get an opus solution, then set up the robot: repeat each day, the point of control is so you can drive to the site set-up and go.
CORS will be the access to whatever the next vertical datum is.That is why they are spending bucks on gravity modeling.
Anyway... I have not heard anybody say to use CORS for every position on every project regardless of the use of the position or accuracy requirements of the project. I would find it completely reasonable to establish a control network utilizing CORS then carry on as normal.
Of course redundancy will always be our friend.
That's illegal in Florida.
I think this is going right over the heads of some who are reading it.
That it is.
It is going to be interesting going forward, the NGVD29 value for one of the communities major elevation points is 3891.52, the NAVD88 value is 3893.95, and now what I'm seeing from the preliminary gravity adjustment numbers looks like the new value will be about 3891.8. Just about right back to the 29 number!
It will be interesting to see how the new models and numbers will match level runs-it continues to improve as far as the shape of the model geoid contours matching real world measurements.
But as far as control goes for highway projects, this board was just discussing pavement being rejected for being 1/4" out of tolerance, does anyone really want to blue top or run C&G with network or CORS GPS RTK with that kind of standard? We have been involved with a number of those projects recently-completely silly specs-but: it was digital levels and robot only after the control was set-up horizontally with GPS static and elevations tied to first order bench marks with levels.
Now they just released FIRM maps all over the country, BFE's from new CORS data will not match at all, so hold on when that happens, here you will be 2' low if you use a new number and no doubt many will!!
> I think this is going right over the heads of some who are reading it.
Exactly.... just what I was thinking :-S
I agree. The information is widely available. In my opinion, if a surveyor is using GNSS (GPS) it their responsibility to stay abreast of current best practices and how the NSRS is evolving.
GPS made it easy for the average land surveyor to benefit from geodesy in day to day practice. I think there are many surveyors in denial. Meaning they wish to deny that they are surveying in a true 3d reference frame with their nifty RTK gear.
I pray our profession will not use the technology blindly to the detriment of society.
GA needs to change
It should be illegal in GA too. But when the major industry leaders, aka lobbyist, are from the only GC to get the highway construction work in GA we shouldn't expect anything different. In fact, I wouldn't be surprised if the survey data was collected by said contractor, who by the way does not have so much as one Registered Land Surveyor on his staff, and yet sets may R/W monuments. Construction work, specifically highway construction work in GA, seems to fall under the idea that Registered Professional Surveyors aren't needed unless something is seriously wrong and worse nobody from the state has stood up to these Meat heads and required them to walk the same walk as every other professional in the state.....GA needs to change