We do a few earthwork projects at the limestone quarry next door. They have an old coordinate system they use for everything that's roughly NAD27 with verticals based on the elevations used to build Ky Dam back in the 40's. I did a site calibration a couple of years ago with my network rover using 8 control points surrounding the site of about a square mile. Used that site calibration to establish a base nearby for machine control for a large drainage pipe job and a new sales yard and plant site. Those designs were provided based on their control and we had no issues. They have another site that needs to be leveled, but didn't have a design, so I copied that calibration from the original job into a new job on the controller, TSC3 with Access, same one used for original calibration. Did the topo, created the design, put the file on the dozer. Set the same base back on the same post with same base location, dozer guy calls and says he's missing grade about 94'. I know that's the elipsoid height, hadn't noticed that the topo elevations were off by that amount. Took the network rover to a control point that was in the calibration and also missed it 94' vertical, dead on horizontal. It seems like the calibration is being used for H, but not for V. Why would that be?
Did you do the calibration using static observations for the control points?
MightyMoe, post: 425051, member: 700 wrote: Did you do the calibration using static observations for the control points?
3 minute rtk observations.
Sounds like one you has applied the GEOID, while the other has NOT.
Newer software will use GEOID even in a site calibration. Tell him to disable GEOID.
The only way I see to add or remove the geoid is to change the coord system in the properties settings. I tried changing the coordinate system to Ky Single zone and add the geoid, the elevations are corrected but the coordinates are changed. If I then copy the calibration and control back in from the original file, corrdinates and elevations go back to what they were. Elevations on control are correct but topo shots are off.
Is this Trimble?
In this case I create the corrected calibration/localization manually. Most don't know how to do this, but it is preferred method.
Will need the
Lat/Lon/Ell and North/East/Elev for each control point.
You could simply add the GEOID Height to each ELL HT, and that may work.
It sounds like you are trying to recalibrate the same file over the top of an existing calibration. I always had trouble with doing that, I would suggest to take the underlining numbers that create the calibration; the original L,L,H shots and calibrate them against the given N,E,EL coordinates in a clean file.
I would do it in the office software. That should work, I would forget what is going on for the time being in the data collector. Possibly you can copy over the new calibration to an office file and import the dc file into it holding the office calibration and it may fix it. It's also possible to edit the original DC file to remove all the bogus calibrations. Just be sure to save and keep track of the original file.
What Lee said 😎
I fixed it the other day when I found it by shooting a couple of pins on the site I had included in he topo. Shot them with a different controller with the same calibration loaded using the previously established base. Figured the difference and adjusted the topo shots by the same amount. True elevations don't matter on this one, only that they are relative to each other.
I just want to know why it didn't work the way I did it the first time.
