Trimble Business Center

Robert Hoy posted 08-08-2024 15:51

How much vertical error are you getting in your transformation?  In your method, there will always be some error.  But you certainly aren't making life easy for yourself.  I always start field observations on geodetic positions, never assumed.

Ronny Schneider posted 08-08-2024 18:01

@ Robert

There are still areas out there with no mobile reception, no control marks around, several hours to get there but you still may want a roughly georeferenced pickup to show it later on GoogleEarth or Propeller.

And if you don't utilize something like Starlink to hook into a VRS your only option is to collect some static and postprocess everything.

@ Stevie

You shouldn't have to transform anything. I assume you've given the GPS points a different name than your totalstation setup points. You can just change the point numbers in your totalstation setup to the GPS point name and recompute the project. Merge points if asked.

Afterwards you can right click on the station point, i.e. the plan view, and create a point derivation report. I'd be interested to see what it says.

stevie matthew posted 08-09-2024 02:27

Hi Ronny

I don't see an option to allow me to change the the total station point to the GPS point, total station point being stn1 and the gps point being stn1.1, sorry if this is obvious.

stevie

Ronny Schneider posted 08-09-2024 02:43

Not up there under "Points".

In your total station data itself, under imported files. You're going to "pin" the whole observation to a different point, the GPS point instead of your local 5000 coordinate.

ian bissonnette posted 08-10-2024 08:05

there is likely a way to do this with transformations. but what we would do and i think what ronny is suggesting is to merge the total station point stn1.1 to the gps point stn1. to do the merge you just change the name of stn1.1 to stn1 and tbc will prompt to merge them together and you say yes. does not matter if you do it in points or down in the observations, i don t think anyways.

then we would delete the 1000/5000 coordinate that the data collector stored for the initial total station setup and all other coordinates the data collector stored because we want the raw observations to be used and tbc will flag the shift from the data collector coordinates to the new georeferenced correct coordinates. select all, then advanced select, dropdown for coordinates, open dropdowns to the imported files and right click on the coordinates that should be highlighted and delete. 

also you will need to delete the azimuth record, because usually tbc will hold this and not let it rotate.

at this point hopefully you can compute the project and the total station should now fall on the gps points. we have not worked this way in a long time, but there used to be a problem if you did not have gps ties on the first total station setup and backsight points then tbc would have a hard time starting the process because it no longer new what to start the total station on. so hopefully your gps is the first two points. if not then you can trick tbc to start by giving it false coordinates near where your total station should start(click on the screen somewhere close) and same for the backsight. give these points unknown quality. give the gps points control quality. run a network adjustment holding the gps control. you will get new starting points for the total station. change the starting total station points to what they should be, again keeping them as unknown quality and run the network adjust now holding how you want to constrain your network. (i guess some of this could have happened before you delete the data collector coordinates as another approach, but the flags tbc will throw will be larger). 

you can save a lot of hassle if you measure the gps points first then use these coordinates for the total station work. you can even use the same point numbers and tbc will merge, but we do not because we like to be able to see the deltas easily by inversing.

hope this helps a bit.

ian bissonnette posted 08-10-2024 08:15

i guess i did not talk about verticals much. how much is the error. it is a hard one to trouble shoot because there are many places that can go wrong. you need to have the correct rod height on the gps, correct total station setup tape measurements, and correct backsight tape measurement. is it always the same amount or different every time. are you using rtk with a fixed pole and one rtk head or two different gps with different phase centers. are you measuring face1/face2 with the total station, if only one face then it might be out of calibration.

there is going to be a bit of an error, but these days with modern rtk we mostly see under 0.01m occasionally 2cm. by shooting rtk first we see this error right away on every new setup and can troubleshoot if there is a tape measurement problem in the field with the total station or backsight.