I'm bidding a pipeline project (roughly 30 miles long). The RFP specs state that the project plans should be prepared in State Plane Coordinates, US Survey Feet, NAD 83 & NAVD 88 datum. Should I assume they know what they are talking about?
I would have to imagine they would want their pipe run calculations and everything to be ground distances. I don't intend to address this at this stage of the game, but what will I be getting into later one if we get the project?
Would you attempt to explain that they will need to have a correction factor to account for differences between plane coordinates and real-word conditions? Or would you just pull the old "you said plane coordinates, so that's what I gave you..." Usually, I prefer to be proactive and at least mention this so the client isn't completely caught off guard.
Of course, bid it to establish State Plane Coordinates and everything exactly as it states on the scope of work. And if you get the job, definitely have that conversation to make sure they understand exactly what they are asking you to do. Some clients might be copying a scope of work from some standard they read about, or got on a generic form, and others may know exactly what they are asking for.
There is no reason to suppose that the entire project can't be done in SP. Many are.
As usual, it depends.
Some States have some very burdensome requirements left over from days gone by. Bidding to meet spec without making a phone call might cost you. There is nothing wrong with a phone call or two to be certain they know what they are asking for. On the flip side don't miss the bid by focusing on that one question too long...
Assuming the project is in NJ and assuming worst case scenario of combined scale factor over 30 miles, you are looking at a difference of less than 20'. To you and I it seems like a big deal. To a pipeline contractor I suspect he couldn't care less. If the contract calls for SPC, do what the contract says and do it right!
Pipe runs, after all, are in slope distances, so the difference between slope and horizontal through varied topography is going to render the grid-to-ground issue pretty moot.
The RFP has stated "State Plane Coordinates, US Survey Feet, NAD 83 & NAVD 88 datum".
Give them that. Anything that may lurk in "what we really wanted" is extra. Don't get caught up in what you think they need due to your experience. If the pipe distances are not spelled out that is their problem. Give it to them at an added cost.
Pablo B-)
Roger that Paul
> The RFP has stated "State Plane Coordinates, US Survey Feet, NAD 83 & NAVD 88 datum".
> Give them that. Anything that may lurk in "what we really wanted" is extra. Don't get caught up in what you think they need due to your experience. If the pipe distances are not spelled out that is their problem. Give it to them at an added cost.
>
> Pablo B-)
:good: :good: :good:
If I did that job
I'd do all my calcs in GROUND distance, and grid brngs. At the end of the project, I'd scale it all up to SPC. So, I'd take a look at where it sits, in the grid. In some places grid to ground is down, and in others it is up, and if it crosses the line, where grid and ground is equal, then some will have to go up to grid, and others will have to go down to grid. Check and see if a SINGLE conversion from grid to ground will work.
Depending on all things, it may need to be done in GRID from the start, and left there. Especially if the project is near that area where grid and ground are very near the same.
What I am saying, is be sure you understand 1.) What SPC means to the data. And, 2.) What the client is going to do with it.
So that all can go smooth. And smooth means make a happy tidy profit, for all parties!
N
I'm guessing it won't matter a bit in New Jersey, but out here it mostly wouldn't mean much, generally about 1.5 feet per mile so 45'. One pipe section.
Are they submitting the project to the State for review/approval?
It sounds very much like a NJDEP requirement.
> The RFP has stated "State Plane Coordinates, US Survey Feet, NAD 83 & NAVD 88 datum".
> Give them that. Anything that may lurk in "what we really wanted" is extra. Don't get caught up in what you think they need due to your experience. If the pipe distances are not spelled out that is their problem. Give it to them at an added cost.
>
> Pablo B-)
:good: :good:
If I did that job
> ....In some places grid to ground is down, and in others it is up, ....
What?? I thought it was always the same way! :-$ ( 😉 )
The state plane requirement is most likely there for Control, Layout and ROW concerns. Rather than pipe lengths. The pipe lengths will be computed along the slope distance at center of pipe on the shop drawings from the Engineers plans. This is very common in pipe industry and DEP.
Actually the lack of understanding here is on the surveyor. Just ask a contractor on an existing pipeline project, and take a look at the plans and shop drawings.
Just wait until you have to recompute 30 miles of alignment from stationing along horizontal distance to stationing along slope distance and along the pipe centerline. There is no software for this, that I know of. I had to create my own.
We face a similar issue on Tappan Zee Bridge project also. When talking with the structural engineers it is clear that the grid to ground scale factor is marginal compared to tolerances in joint placement, steel expansions and other variables per section of steel placed.
For example we have 0.92' difference in grid to ground on TPZ in the 3.2 miles of bridge. Brake it down per section of bridge span to be installed. Each span is about 400ft or less , with the main span at 1700'. Over the 3.2 miles, that's just 0.02' per span in the grid to ground scale factor.
Lee Green
If I did that job
Well, Tom, I reckon you could be right, but there are places on earth, that are below sea level....... maybe not in usa, Maybe Washington DC has gone off the deep end though!
If I did that job
Unless the elevation is below sea level (okay 0 gravimetic potential) the sea level correction factor will be less than one. But you can easily have a grid scale factor greater than one depending on the projection and the points relation to the central meridian or standard parallels. Thus the combined factor can, and often is, greater that 1.
If I did that job
I have not strayed real far from home.
Where I work, combined sf is usually slightly over one.
N