Elevation busts during traverses?

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Elevation busts during traverses?

Postby delliottg » Thu Jan 03, 2008 12:35 am

Two of our crews are reporting this problem today (02 Jan 08), which also happens to be the first day we've worked in the new year. They're seeing elevation differences of up to 0.15' (fifteen hundredths of a foot) between backsights and foresights. Is anyone else experiencing this? If they simply use the instruments w/o a data collector, they're seeing differences in the thousandths, not hundredths.

They're using two different Allegros, one's a CE & the other's a CX, both are on version 2.02, and both using Sokkia Set 2B instruments.

Could this be some sort of setting? Both of them are using scale factors for their traverses to keep on WA State Plane Grid, something we've never done before. However, one of the crews was out last week (last year) using the scale factor and had no problems. This leads me to believe it could be some sort of year related bug.

Any advice would be appreciated, we don't want to waste another (two) day's work for two crews.

David
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Postby tstrickland » Thu Jan 03, 2008 12:03 pm

I have also noticed a difference, going back to v1.x. It's not something new in v2.

I have a theory that the software doesn't account for the internal axis instrument compensation, and / or C & R when doing a backsite, but I'm just guessing.

It doesn't appear to affect traverse integrity, just the backsite shot. I have staked out the backsite point after getting the backsite shot during setup, and it will check within a hundredth or so.

I have basically just ignored it. I don't know what the cause is, but it don't appear to have any adverse effects. However, I wonder if this comes into play when using remote benchmark or resection. I don't know.
fwiw,
terry
edit: By the way, I use Topcon equipment. How did your traverse(s) close? Could you tell any difference much in the vertical?
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Postby Jason » Thu Jan 03, 2008 2:48 pm

I am not aware of any errors here. Have you tried 2.03? If you still expierience problems with .03 we can report it in for repair.
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Postby delliottg » Thu Jan 03, 2008 3:13 pm

Jason, we have not tried 2.03, and weren't aware it was available as yet. Did you make changes in this area between versions? If so, can you detail the changes, if not, can you explain your logic?

More information now that I've had a chance to speak to the crews this morning. They were both using Sokkia Sets (a 2B & 3B). Both collimated their instrument's vertical circle before the traverses with results less than 8 seconds. One crew was seeing vertical errors of up to 0.25' while the other was experiencing vertical errors of up to 0.16'. They both state that when moving back to a previous traverse point and checking ahead they would see about 2-3 hundredths, but checking backsights, they would see the large errors.

I will be going through the raw data sometime today. We don't have a closed traverse yet, so there's no way to see what the closure is yet. One of the crews did a Set Collect on one of the points and got a vertical 0.20 different from what the traverse said.

The commonalities are:
Sokkia Set instruments
Allegro data collectors
Localization scale factors set
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New year.
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Postby tstrickland » Thu Jan 03, 2008 3:59 pm

I haven't used 2.03 yet with TS, only rtk gps. It may now be resolved.
I have noticed elevation busts in the past only when checking the backsite. I never knew what caused it, but it didn't seem to affect my traverse vertical closure, only the backsite check. I also work on state plane with a combined scale factor, it that matters.
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Postby JG24CV » Fri Feb 15, 2008 11:22 pm

Try hitting "set angle and read" and then try hitting just the "check". Do you get different results? I do. Usually when I have trouble with the verticle check of my backsight I hit the "check" button and it's a much better result. This is with an Allegro CX v2.03 and a Leica 1200. It has not changed since v1.6x.
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Elevation on a Backsight Check

Postby Artanian » Wed Feb 20, 2008 3:01 pm

Hello,

If this has been happening since version 1.65 or earlier then it sounds like a difficult issue to reproduce.

From reading the posts it does not look like its instrument specific since a Sokkia, Topcon and Leica are mentioned in this thread.

You could email support@carlsonsw.com along with a detailed description:

1) how often this Elevation Difference issue happens {once a day, once a week, 6 times a day}

2) You could attach an RW5 and CRD file to the email from a job where this elevation bust shows up in the Raw File with a note of which line or which setup the problem occurred on

3) Is it always in a specific routine like "Store Points" or "Stakeout Line"?

4) Next time this happens you could try the workaround of doing a "Set Angle & Read" then a "Check" button as mentioned in an earlier post to clear out the Elevation Discrepancy.
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Is this fixed yet?

Postby treekiller » Thu Feb 18, 2010 4:00 am

Has this issue been addressed. We have the exact same problem. I have even gone so far as setting up both the backsight and forsight tripods at the same HI and HR, shooting them and then swapping back and forth. With Leica equipment the heights from the gun and prism are the same. The error seems to be worse if there is any change in the ground elevation.
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