How can you prove that the coordinates & distances in your CAD file are "ground" values? Unless you're stating the values you pick off of CAD do not agree with the horizontal & vertical plan sheet you provided?
The ROS which this is all based on has more bearing and datum information than i have ever seen on a survey. It clearly states ground coordinates and the accompany grid to ground scale factors which much be used to duplicate their system. I don't know what hardware and software you're using but i would set it up exactly as the information shown on the survey, scale factors included. That's what i would do...and then survey the points and check the residuals.
The control sheet looks to be for a municipal infrastructure survey. It was Mid 2010's and should be very recoverable unless all the points have been removed during recent construction. The data given is similar to a DOT data sheet with considerably less information than DOT will usually provide. How the SP coordinates were converted to ground is a bit lacking. It looks like the millions of feet were removed, then something else was done. But whatever happened, the numbers work, grid to ground. Don't have time to get into it, good luck, you've got everything you need.
It sounds to me like you are not an LS and are doing the layout work for your employer, who is a contractor, and that is what it is. Assuming that I am correct in my assumptions, I would not be wracking my brain trying to figure out what the problem is. The fact of the matter is that if you are confident that your equipment/procedures are sound, it seems to me that's all you should be concerned about.
The bottom line is that your employer, or their client, paid another surveyor to set the initial control points that you are trying to work off. If I were you, I would pass this issue of to your management and let them run it up the chain to whoever paid for the points to be set.
Any adjustment approach that you take to rectify the problem puts you in a position of assuming liability from the second that you make adjustments and that liability will carry on with every stake you set. Personally, I would not set a single stake without tight control values provided by the surveyor who set the points.
You have not said anything about what you're staking or how the control points work vertically, nor the size of the project (in area). If the vertical works within reason and you are just pushing dirt, 0.15' really doesn't matter. If you are staking something that needs to be tight, that's a whole different story, but, as I have said, it isn't your problem, until you make it yours. I am a PLS and do a ton of layout on projects that we didn't initially establish the control on. Before doing anything, I check the control provided and if it doesn't work, within reason, I kick that back to my client and tell them that they can either get the other surveyor to fix the problem or pay me to do it before I set anything.
It appears to me that the surveyor has expressed what he has done - in terms of the control - very clearly. It is the engineer that needs to explain themselves. My guess is that they used the scaled to ground coordinates in the left hand columns. You have your work cut out for you, starting with collecting some field data of your own on the control and the already staked works.
If the control has issues, why would anybody proceed to stake things? Engineer, Surveyor or whomever, I'm kicking that can back to my client to sort out before I ever set a stake.
You are spot on Chris!
The scale of the job is about 50 acres. and I am laying out dirt work and gridlines for batter boards,
Sump pit walls, yard piping, etc...
Thank you guys, I mean it, it helps a lot!
Do these Combined Factors apply to just GPS or would you put the grid to ground in your Total Station?
Or at least test them with the surveyor's control with the TS.
I'm from NJ and have not seen a contractor use batter boards in 25 years or more.
Take a look at the coordinates of all the NSRS horizontal control points - they are given in geodetic (referenced to the ellipsoid) and grid (SPC or UTM); they are not expressed in terms of ground coordinates. If a plan set or map says it is referenced to the Nevada State Plane Coordinate System then the presumption is that dimensions and coordinates are grid, not ground. If you want to lay the plans on the ground, you have to scale the grid distances using the inverse of the scale factor and elevation factor.
This is a big reason why NGS wants to move to Low Distortion Projections (LDP). The closer the grid can be fit to terrain, the closer grid and ground values will be. The problem is that you cannot accomplish that over large areas like SPC and UTM typically cover.
Moving to a push-a-button-and get-an-answer mentality without understanding the fundamental principles will result in unresolved errors. SPCS date back to the 1930s - by now we should have a pretty good handle on them.
I just saw this based on the Trimble report they have not scaled to ground. If they had a lay long would have been added automatically. The scale of 1.00000”” is bogus. Unless I get a chance to read the rest of this and someone else figures it out. I would say those values are grid coordinates. So plug a couple into NGS NCAT. I bet if you take the combine factor of two on your longest line and scale your shot ground distance you will see you match. Now they could have been swapping between grid and ground so they sent the wrong report. You are 1:1 on grid. If the design is ground they need to re run the report so you not only get the project scale factor but also the lay long ellipsis height they used to compute the scale from so you can re create it.
I thought that as well but don’t see a lay long in local settings. I ran a report not long ago that glitched and I re ran it then the local lay long came in and it was fine.
If someone designed this facility on state plane coords and want it built at ground dimensions I'll eat my shoe. That did not happen. If they give dimensions of the face of the building and they give coords for the corners of that face, check to make sure the coords inverse the same as the given dimensions. That is the size they want their building built at. Now if you scale up state plane coords it will move everything north and east. You should have been provided control coords that were already scaled. Perhaps you were not. Many times people have scaled from a point on site instead of from zero-zero. You say the other surveyor has laid grid for the building. You should be able to calc those grid line points. This will enable you to work back to your control to determine whether you were given state plane coords or coords scaled to ground. You need to use coords scaled to ground other wise you will end up constructing a scaled model of the building instead of a full size model.
Scale up the coords you were given. Use these new values. Your distances between control points should hit and you should be able to stake a grid intersection and agree with what the surveyor staked. If not they may have scaled from a different point on site. If so you need to find out which point. Subtract that northing and easting from all of the other points you were given and then scale those by the combined factor. Use these new values and check the control and the grid intersection.
Assuming the control problem is one of state plane coords. Perhaps it is not and you were just given a bad coord for one point, but it sounds like your misses on distance between control have all been proportional and close to the sites combined factor.
Better yet. Ask for 2 coordinate values for each control point. 1 set on Nevada State Plane East and the other set of coords to be Local Ground values. This would be very simple for a surveyor to provide.
