LGO 8.3 Traverse Adjustment

do you own LSA option, or are you just hoping for compass adjustment in tps processing?

Enter the GPS as control points and your traverse should translate and rotate over it within tolerances. I generally chose my best GPS observation as the fixed control. I do not know how well you carried vertical around the traverse, but I am confident to personally hold the GPS elevations or the traverse elevations as seems reasonable. That is you may not have sufficient observation time to take a GPS observation over traverse.

Paul in PA

Thanks for your response.

I'm fairly a newbie to LGO so I don't know how to go about what you suggested.

I use a TDS Ranger 300x data collector to collect RAW data. Am I correct to assume that somehow I would need to import that data into LGO and then manually type in the coordinates of the GPS tied control points replacing the "bad" coordinates for the same control points shot with a total station?

No I do not own the LSA option.

Isn't it possible to do a coordinate transformation to adjust my total station points to fit the GPS control points that I shot? Basically doing a 2-step transformation in reverse?

I use a different brand of software. It is possible to export the points from my GPS software to import into my CAD, but since it is only a few points it is easier to just type the coordinates in.

Assuming my traverse points are 101-107 and I GPSed 101, 103 & 104 I would draw points 1101, 1103 & 1104 on a new layer, GPS-SPC, then lock it and freeze it. I would redraw them on layer GPS-SPC-Scaled, renumber them to 2101, 2103 & 2104 then horizontally scale them. I would compare the points to make sure I got the scaling right. I would then translate my project horizontally and vertically to my best GPS point using the OPUS results to choose. I rotate the project to a best fit. Generally I do not adjust if my traverse work is within my error budget. If I want to remaining on a local bearing system I rotate my scaled points, renaming the layer, instead of rotating my project.

What I do, can be done in any software, over adjusting is just not necessary on most projects.

Paul in PA

My survey is a 4 mile linear topo basically in a south-north direction with some curves in between. It is an open traverse with topo sideshots taken from each occupied control point (49 control points).

I GPS'd the beginning control point and the ending control point plus several in between for a total of 13 GPS tied control points. I basically want to do a transformation of my local coordinates to put them on my GPS coordinates.

I started my survey on assumed coordinates with an assumed bearing with the intent to rotate them to a known basis of bearings based on found monuments afterwards. Well, I discovered after the survey was done that our open traverse did not end up in the same spot as our GPS shots (about 4 feet in a east-west direction) and that's why I want to transform my conventionally shot points to fit them to my GPS points.

The only software I have available to me is Autocad Civil 3D 2013 and Leica's LGO program since we are using their GPS 1200 receiver.

Hopefully I conveyed what i'm trying to accomplish clearly.

I Disagree On The GPS Placement

In order to adjust a long open traverse you need to start from a fixed pair of points to a fixed pair of points, i.e. Geodetic monuments. Simple pairs of GPS points do not meet that criteria. You need a triple at each end such that your immediate field traverse can confirm the precision of the three. Then setting your traverse on a pair compare it to the results at the other end. Once you have a reasonable fit with at least 2 at each end, then you can compare to random GPS along the way.

If you do not have concurrent GPS occupations of your GPS point array your coordinates are not as precise as you think. Even long concurrent GPS endpoints might work but be prepared to see a lot of adjustment.

Paul in PA

yes. in lgo, key in (to override) the reference coordinates from what they were (somewhat estimated, not processed) with the gps processed. go to tps processing, select update automatically. right click setups, and reprocess.

that should force the transformation you need

there are other ways, but this one seems like it would suit you best.

hit me later for more

Here is a picture of a portion of my survey imported from TDS RAW into LGO.

I don't know if I'm understanding your instructions correctly but I edited the coordinates for a control point with the coordinates from my GPS tie for that same control point and all it did was move that control point along with the sideshots taken from that control point to a different location. This is due to the fact that my survey was started on an assumed 10000,10000 coordinate system and it was now moved to california coordinates instead. but anyways, it's not giving the results i'm looking for so I know I'm doing something wrong.

I am pretty sure it helps to start your traverse on a GPS point at one end and have the other end coordinates relative to line to the last GPS coordinate. You want your GPS points to be considered positions with error circles and your traverse to be angles and distances. if you do not start close to your final answer the adjustment can sometimes "Blow Up".

Paul in PA

Normally, if I wanted to perform a coordinate transformation from State Plane to some Local Coordinates, on my Leica RX controller, I can do a 2-step transformation using at least 3 common points between state plane and local. That way, I can do stakeouts or collect additional topo on local coordinates using my GPS.

But now in my current situation, I would like to go in reverse; from Local to State Plane essentially. But I am unable to do so within the RX controller. And I know there is a way to do this within LGO but since I have actually never done it, I don't know how to go about performing a Local to State Plane coordinate transformation.

Ditto what Paul said - the analysis needs to use the total stations's angles and distances ONLY, along with GPS coordinates, but yours seems to be keeping the other 10000,10000 based coordinates generated from the TS data.

The hardest part of using software is knowing what it is doing for you.
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Paul's post below about using sets of GPS points would greatly improve the checking of GPS accuracy. It isn't necessary for getting an answer, but would sure help indicate how good your answer is.
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Are you converting everything to SPC grid (i.e. taking the surface distances down to grid)? That shouldn't be an issue in the short east-west direction, but might be significant in the long north-south direction, depending on where you are.
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I'd enjoy looking at your RAW file and GPS coordinates to see what I could make of the problem, if you can share (use the email link in my user name above, and if the data won't fit in the email, I'll reply with my actual email address).

I'd run it with my home-brew least squares program (no liability assumed for inaccurate computations).

send me your data, both gps and tps. i'll give it a run here. email is in my profile