Carlson Geiod file edit...

I can't give you step-by-step directions at the moment, but I know that you can upload the correct geoid into the DC and reprocess the job.

In general:

1) Load correct geoid in DC

2) Open job on DC and switch to the correct geiod file on the localization tab.

3) After #2 above I believe you'll be prompted to reprocess the job or something similar.

> Can you edit the geoid file in your RW5 file in CS 2013?
>
> We did not have a geoid file for the area we worked in and used one that was about 30 miles away.

In Carlson 2013:

1. Issue the Survey -- Edit-Process Raw File command and open your RW5 file.
2. Once opened, run the Process (Compute Points) -- GPS.

In the resulting dialog box, you'll be given the option of selecting a geoid model (e.g. 2012a) to apply to the GPS observations.

Otherwise, it is also possible to perform similar options in SurvCE (File -- Raw File -- Process) on the data collector and even the "PC demo" of SurvCE that you can run on your office computer.

I hope this information helps.

Stephen - I'll try that

Ladd - I'm trying to change the .gsf file (geoid) that is used in the data collector.
Not the Geoid09 file in the GPS process program, unless that will give the same results. When I process the GPS raw data file in CS 2013 it gives the same results as the SurvCE did using a .gsf file centered about 30-35 miles away from our site. Would that mean that the GPS process program is just reading the results that SurvCE produces or does it process from scratch using the Geoid09 file???

Thanks

Carlson phone tech support says that you can't change the geoid file after the data is collected unless you have the GNSS software. You have to have the correct Geoid file loaded before data collection.

It has been a while since I have used SurvCE, but the last I knew it was possible and I had done this process a couple of times. I believe you needed to open the job, apply the geoid file, then process the the raw data inside SurvCE.

Here's how it works in SurvCE 3.02:

1) In SurvCE, open Equipment, Localization, GPS tab, and select correct geoid,
2) Open File tab, Raw Data, select raw file, select Process GPS, double check that the correct geoid file is being shown then click the green check mark to start the processing.
3) When it finishes it will show a Review File screen, either save (the review file) or click the red arrow to exit the screen.
4) You will return to the Raw File menu, click the red X at the top of screen and click YES to save the coordinate file changes.

I just collected a sample file in my backyard with no geoid file loaded. I noted the elevations of the five points in the file, then ran through the above process using Geoid-09. All of the elevations increased by approximately 100 ft once Geoid-09 was applied. Once again I noted the elevations and then re-ran the process with Geoid-12A. This time the changes were in the .02 ft range. Finally just for kicks I reprocessed back to Geoid-09 to be sure that I'd get the same numbers again.

It goes without saying that you should back up both your raw file and your coordinate file before doing this just in case something goes sideways.

Stephen has It correct. Also, geoid files can be produced in Carlson Survey (Survey -- Data Collectors) or Carlson Xport.

We've just done a small (all points within 400m square) RTK-GNSS topo on a coral atoll (flat, 3.5m asl) - WGS84 one point localisation to UTM coordinates of a existing control station "A", provided by someone else. Didn't use a geoid.

A check shot on another control station "B",?ÿ185m away, gave good (16mm) horizontal correlation to the stated coordinates, but was 120mm out in vertical. So back in the office, started to wonder if geoid-ellipsoid could be that much "different in shape" over that distance, assuming that the stated elevations of the control station were done by optical levelling.?ÿ

So tried Carlson X-port, got a piece of geoid EGM08, and had a few cracks at reprocessing the survey data, as per the instructions above. Instructions above are good, but got wacko results, e.g two check-shots on the same temp-pin are "identical" in the unprocessed file, but after processing it puts them 1m different horizontally and 3m different vertically. The survey was done over 3 days, so there were 5 localisations to the same control station (and the two pin checks were at different times, i.e. on different localisations), and therefore I assume that "processing" can't take this into account on the whole survey, and that is why the process results are haywire. The only way to get this correct would be to process individually the survey data applicable to each localisation set.

So to take the easy route, is it reasonable to assume that 120mm difference is not going to be geoid-ellipsoid related over that distance, and hence the apparent anomaly in stated elevation between A and B is due to something else, like a levelling error?

Posted by: FLS

Carlson phone tech support says that you can't change the geoid file after the data is collected unless you have the GNSS software. You have to have the correct Geoid file loaded before data collection.

Wow, I didn't know Carlson was so limited in the GEOID.

?ÿ

Topcon Magnet on Tablet can re-load any?ÿGEOID, and all RTK data is recomputed automatically. But worse, why carry such as small GEOID that it does NOT cover your entire state or entire project area??ÿ I work across the entire continental?ÿUS and therefore?ÿI use G2012bU0.bin

I don't think what is happening is what you think is happening. Outside of it's area a Geoid Model can't do anything. A Geoid height is applied to a lat, long position, 30 miles away it won't give an answer, usually it will give an error message and not allow you to work.

With no Geoid your elevations will be on the Ellispoide, amount 115ft low around here.

Carlson's latest versions of SurvPC use a geoid file that covers the Continental US. It's located in the default Carlson projects folder - data - geoids.

Correct. But if you are outside that area, you need to use Carlson X-port to cut out a piece of a geoid file and load it into the DC and then into SurvCE or SurvPC. (I'm going to have a crack at answering my own question above, soon).