Trimble S6 - Poor Traverse Closures

Very good point. I'm going to re-check each tripod/tribrach setup again. Then I'm going to re-run a 6 leg traverse using those setups with the S6 and with then with the old Sokkia. If the Sokkia gets half the misclosure of the S6 again, then it has to be the instrument.

I didn't previously notice that your traverse legs are 2k-5k feet. You should be carrying and using a barometer. The ppm corrections in your distances will be significant. The pressure you get off weather.com on your smartphone are corrected to sea level. You need the pressure at your location.

EDIT - 500-700 feet is still plenty long enough to justify the barometer.

The S6 has an internal barometer, which you can select to use at the initial "Corrections" screen in Station Setup.

Have you turned autolock off and tried a few sets manually between fixed objects (not prisms)? Do the F1 & F2 angles check OK?

When you are consistently closing traverses at 1:50,000, one can hardly call his TS cheap. A fantastic deal would probably be a better term.

I've heard on here that the S6 and other robots are not the first choice for simple traverse thru the woods surveying and that they are more suited for many shots from one location and most of them being ground and non monument shots.

The S6 is a great tool and perhaps you are expecting too much from it on a simple task that the Sokkia TS is more suitable.

0.02

Yeah, it appears that it is definitely an angular error. I took it to the baseline and the distances are perfect. My next step is running a relatively short traverse loop with the S6 without using Autolock but still turning rounds to every station. I will see if the results are any better than when I ran the same loop previously (with all the same prisms, tribrachs etc). Finally I am going to run it with the Sokkia as well and compare. I will post the results.

Probably a whole loop isn't necessary, at least not at first. A single angle setup, turned with your S6 autolocked, then your S6 manual, then your Sokkia, all using the same targets and instrument tribrach should tell you if there is a problem with the S6 or not.

Stop using autolock. I bet the problem will go away.

I don't trust autolock on a non-active prism.

I'd take your gear to the local defuct kmart parking lot and set up a 3 legged traverse with basically equal length legs, 300 feet+/- long. Turn 3 sets per station- not much time at all- make sure you're recording distances to the BS in your sets- Track Your HIs/HS and things should become readily apparent...

My S6 cranks angles just fine- but I always included redundant legs/angles and perform a least squares adjustment of my NETWORK in star*net.... closing a traverse is only a partial analysis of your work...

I agree, turn off autolock. Bet you that fixes it. I once did a traverse, and from what i could tell, I traved parallel to myself. If that makes sense. I came back with a Leica 1105 and traved it and my distances were good but my angles were off because the crosshairs are not on the prism with robots all the time. Shooting it with autolock on in a traditional total station style trav was no good. Also, try heavier wood legs, found way better results with them.

Do not use any 360 prisms in your traverse if you are, they will get you bad results. Trimble 360 prisms should only be used for topo and stakeout.

The S6 has a built in barometer in it. Only need a good thermometer.

Thanks for the suggestion, I will try that. Things have picked up here at work and haven't had time to run the test loop. Trying the 3 leg traverse will probably be much more do-able with my time constraints.

Just wanted to refresh this for anyone else who may have this issue.

We ran into exact same issue (relatively same traverse length and misclosure).

I discussed with our Trimble representative.?ÿ

Solution Part 1 (and most important): Turn "active tracking" to "semi-active" in prism settings. This tells the gun to look for the glass and not the lights.

Solution Part 2: Make sure prism is rotated to have one piece of glass perpendicular to gun just as you would a convention prism.

This solved our problem.?ÿ

Sounds like a ~$3000 traverse kit would've saved you a lot of money in the long run...

How long are your loops?

I've found that when using a -35mm offset prism that isn't Trimble traverse kit -35mm, use a custom prism type and key in the offset.

Having some Leica prisms, I toggled between custom and traverse kit and was consistently getting different readings.

How much of a difference??ÿ You know you can't use the offset printed on a Leica prism for any other brand of equipment...:

Found this with a quick search:?ÿ?ÿ https://www.lasersurveyingequipment.com.au/latest-news/42/leica-prism-constant-explained.html

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It was sub-hundreth for x,y & z, but there was always a difference.?ÿ I didn't take the time to find out if the errors were compounding over multiple set ups.

Is it just me, or does 1:20,000, 1:30,000, and 1:50,000 sound like good closures? I have topcon gpt8205 that I have gotten over 1:50,000 with, but I also get many 1:20,000 + closure with it as well and never worry about it. I can't say I ever remember getting over 100,000 with it. I call that luck.

This is all singling the angles and running the older style A6 360 prism with it, and taking the traverse shots with tracking mode which I assume is the same as autolock on a trimble.

I am doing primarily residential and rural boundary and residential home construction stake-out work.

I have been meaning to upgrade the prism which I will probably post about soon in another topic.

I read that you are using 30mm offset prisms and I assume tilting ones at that, so I guess my comparison is not totally valid.

The comments about tripods are spot on as you do need the best ones with robotics or at least in my experience. I had some closure issues when I first got my GPT8205 Topcon, as I continued using the same tripod I had with my conventional total station, but I upgraded by a suggestion from Troy Deaton to a Crain Trimax and I have had good results ever since. I have been using that same Crain since 2007 too.

Ben

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