Greetings everybody, I am a lurker here making my first post.?ÿ
Currently, I am setting up a road reconstruction project (using Pocket 3D, Hiper VRs and a localization control method) and I have a mysterious issue. I have 4 control points measured, with pretty good residuals, and the project scale is coming out to 1.00002.?ÿ
I went to stake out one of the control points I had already measured. When I place my rod on the point, facing south-ish direction, I am basically on it to within an inch (call it GPS error). But, when I rotate the rod on the same point and face another direction, all of a sudden the stake out is telling me I need to move, say 2-3?, yet I have been on the same control point the whole time.?ÿ
Can anyone explain what is happening here? This isn??t the first time I have noticed this, it has happened with an old set of GR3??s and now a new set of VR??s. I am missing something somewhere. Thanks a lot.
Sounds like the rod bubble is not calibrated. We use these to check ours weekly https://www.stakemill.com/poles-prism-and-range/replacement-parts/sokkia-pole-peg-adjusting-jig-5195-01?cPath=121_257_987&zenid=ngd5n6ragslbu4pd76ce1dct50
Rod bubble, as bstoffy says, it may have made your "localization" messy.?ÿ
Thanks for the replies! I went through the same issue in the summer, tried a couple rods (didn??t check the bubble though), and didn??t have any improvements. After I wrote that post earlier I went out and stood on another control point, and yeah same issue. Facing one direction I am on the mark. Rotating maybe 90 or 180 and I??m being told the point is 2-3? away, even though I??m on top of it. I??m kind of flabbergasted. I have an older rod I could try and see if there??s a difference.
Add a second rod bubble at 3ft. Have the two bubbles calibrated by your dealer or surveyor. Then compare each bubble. When out of sync recalibrate.
Also don't treat the rod like a shovel in bed of your truck. Treat it like at precision tool, keep it the cab of your truck.
If you don't think it's the rod bubble put the receiver on a tripod over the point, level it up, center it then rotate it.?ÿ I doubt you'll see the same thing.?ÿ If you have a bipod for your rod you should be able to see 0.25' if you step back a couple paces and compare it to a plumb bob string.?ÿ I have zero experience with Topcon GPS receivers but Hyper VR's don't have an internal bubble that could be throwing things out of whack do they??ÿ?ÿ
Crap! You will see it, or more likely half of it, using the tripod test. That is if you were facing generally the same direction on each of your original measurements on the control points when you built your localization.
@cameron-watson-pls I was wondering if the direction in which I was facing during each control shot had an impact. That’s a good idea to try with the tripod. I am meeting with the Topcon dealer in the morning, I’ll ask about the VRs, I’ve talked to others who know more than me about the equipment and nothing seemed to jump out at them about any potential internal issues. Thanks.
Sounds like your rod is out of calibration like others have said. I like the tripod idea as a check. I also agree with Lee, you have to protect that bubble. I keep my rods in pvc pipe with foam pipe insulation in the back of the truck. I also check them for level once a month. The pvc with foam protects them well and I rarely have any adjustments.?ÿ
@tkc12-3” is a crazy amount of error to have with a bubble. You can also check it yourself by setting your rod up with a bipod and checking the plumbness with a gun with the bubble facing one direction then rotating the rod 90° about the same point and check for plumbness again. Another way is to mark the top of a doorway, hang a plumb bob and mark the floor. Set your rod on the point on the floor and check the top of the doorway.
I wonder if it also might require a tilt calibration in your VR's. You can disable that in pocket if you want.?ÿ?ÿ
?ÿ
Here is a youtube video on how to do it manually.
?ÿ
?ÿ
?ÿ
Thanks to all who contributed; it ended up being the rod. I had a similar issue with a set of GR3??s, so I didn??t think it would be the tilt calibration (and I don??t know if you can have the tilt feature on before the site is localized or not?). I happened to have two other rods in my truck, so when I got there I just quickly held them against a level and sure enough the one I was using seemed warped a little - even with this rough check. I localized the site again using another rod and everything seems to be back to normal. Thanks again.
I'm considering this a lesson too; to say I??ve been neglectful caring for my rover rods wouldn??t be completely off.?ÿ
I'm guessing most of us had similar experiences. Back before GPS and robots it was simple to check the rod. The instrument man would sight along it from ground to prism to check them. I had a crew doing an ALTA and couldn't get a decent check-in. I went out to the field with the party chief and he held the rod and I looked through the gun and it looked great. Then I made him spin it 90 and it was way off. Seems he held the rod pointing to the gun with the bubble on his side every time, so the instrument man never saw the tilt. Live and learn, that one was about .1' leaning forward each time, needless to say the traverse never worked.
The best way to learn is when you get burned by something.
Using two bubbles has been SOP for me for a long time.
Although, a bent rod is a different kind of issue.
@leegreen I accidentally ended up using this idea. I had several 2m rods and one day I happened to combine two pieces that both happened to have a bubble. Worked so well, I just kept that combination going as a way to keep things in check.
Another vote for rod bubble needing adjustment. After you have done it you should re-run your localization.?ÿ You could have the bubble adjustment done professionally but it is not difficult to do yourself, nor are any special tools needed (just an allen wrench). Look for youtubes, there are many. There are jigs of various sorts available but it can be done with nothing more than a pickup trucks open tailgate and bumper.?ÿ Then check it regularly.
I make a habit of tying things, spinning the rod 180?ø, tying again, and using an average. This procedure continuously checks the rod bubble adjustment.?ÿ ?ÿ ?ÿ
Not sure how you could see both bubbles on a screw together two section rod. Either they would facing each other, one up and one down. Or if both were facing up, then one level bubble would be at 6ft. Besides that the rod height would not 2 meters.
@norman-oklahoma I will send it away to our dealer to get calibrated, but yeah it's something I should look into myself. I definitely re-localized, as I didn't have a truly accurate idea how my control points would work when shooting with the new rod. That is a good way to keep an eye on your bubble. Thanks for the suggestions.
Was looking for a different old post and happened across this one.?ÿ 2 sections, one top and one bottom.?ÿ they were not a matched pair from the factory as I purchased 4 2-meter rods at the same time.?ÿ both sections had a bubble factory mounted on them.?ÿ One near the top of the bottom section and one near the bottom of the top section.?ÿ about two foot of separation between them with both facing upward.?ÿ while not a matched pair, close enough to 2 meters that it doesn't show up with a tape measured length of the assembled rod.
?ÿ