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Traverse adjustment points

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(@fisad)
Posts: 3
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Hello:

I have a problem with six Leica circular prisms.
Every time I make an Setup, I can not get good results of calibration and accuracy. I have done the setup with different combinations of prisms.
The best results I have obtained are E: 7, N: 8, H 5.
The coordinates of each prism are from another surveyor.
I work with a Leica 1200 total station and a panel with SmartWorx Viva system.

My question is: is possible to adjust the coordinates of the prisms?. If possible, which would be the method used to make corrections to the coordinates. I would like to know the manual calculation method and procedure data with the total station and a program (I think in the case of network setting or adjustment of polygonal).

Would appreciate the help and guidance.

 
Posted : January 3, 2014 1:49 am
(@norman-oklahoma)
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Slight language issue here, perhaps. I'm guessing that you are setting up by resecting to control points set by others and getting residuals of 7,8,5 millimeters.

If so, there is a possibility that the "error" is not really an error at all, but merely reasonable uncertainty.

There will be a certain amount of uncertainty in the supplied control. You may not have any control over that. There will be a certain amount of uncertainty in your measurements. Perhaps these could be reduced by turning more sets of angles, etc.

Check your tribrachs and rods for adjustment and calibration. Has your instrument been recently tested vs. a standard baseline? I don't mean at the factory or repair shop.

I believe that resecting is more commonly used internationally than it is in the US. Here, we more commonly set up on one of the control points and backsight another, then work from there.

 
Posted : January 3, 2014 6:15 am
(@paul-in-pa)
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Are You Assuming The Other Surveyor Was Perfect ?

Are you assuming he had perfect setups?

Are you assuming he had perfect manual measurements for rod and instrument heights?

Are you assuming his instrument was perfectly adjusted to climatic conditions?

Are you assuming you should work without an error budget?

You can and should adjust your prisms in the prism holder such that they are consistent in distance and check that the prism center is on the target center.

My tolerance on adjusting my prisms for distance is 1.5mm, that becomes a part of my error budget. From time to time I set all my prisms on the same tribrach and check them for distance.

Paul in PA

 
Posted : January 3, 2014 7:07 am
(@fisad)
Posts: 3
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Topic starter
 

The initial setup was done by another company three years ago.

We have checkpoints issued by the municipality where the project is located, but these points are several miles away from where we work.

Our idea is not to make the initial setup again, but rather, try to adjust the coordinates of existing prisms for better precision with the measures. The uncertainty results are acceptable for structural work but not for detail work. An error or uncertainty in the height can be cumulative and detrimental to the progress of the work to the higher floors.

The instruments with which we work are calibrated and adjusted by the service and calibrated in the field.

We have worked with several instruments and all have the same result, so we can say that the problem is in the coordinates provided by the other company. The problem may be because at some point a bird sat on the prism, which is very common here, or that, after two winters, the magnets have moved. There are no earthquakes so it is not possible that the buildings have been moved.

Our idea is to know if there is any method to determine how much is the error of the coordinates.

If we make control of the prisms with the control points of the commune, need go about eight miles to the point of location of the prisms.

 
Posted : January 3, 2014 7:37 am
(@martin-f)
Posts: 219
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Network adjustment points

It is possible that your measurements are superior to the previous company's or that the control point prisms have shifted, especially if they've been held in place by magnets and exposed to the elements and birds over the years!

This is surely a case requiring network least-squares analysis, where control point coordinates also have uncertainties. (BTW, "traverse" is probably the wrong word.)

 
Posted : January 5, 2014 1:17 pm
(@ralph-perez)
Posts: 1262
 

> Hello:
>
> I have a problem with six Leica circular prisms.
> Every time I make an Setup, I can not get good results of calibration and accuracy. I have done the setup with different combinations of prisms.
> The best results I have obtained are E: 7, N: 8, H 5.
> The coordinates of each prism are from another surveyor.
> I work with a Leica 1200 total station and a panel with SmartWorx Viva system.
>
> My question is: is possible to adjust the coordinates of the prisms?. If possible, which would be the method used to make corrections to the coordinates. I would like to know the manual calculation method and procedure data with the total station and a program (I think in the case of network setting or adjustment of polygonal).
>
> Would appreciate the help and guidance.

Are you describing this type of setup

If so, did the previous Surveyor leave his prisms in tact?
If he didn't are you adhering your own prisms?
If you were left with a 5/8" bolt and your screwing in your own bayonet check to make sure you're using the same size bayonet.
All things being equal if you are using ATR, and both guns were in adjustment. The resections should be within reason.
If all of the above are correct, then I would independently check the individual prisms coordinates.
Another thing to check would be that the targets are pointed toward the gun.

Ralph

 
Posted : January 5, 2014 2:22 pm
(@fisad)
Posts: 3
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Network adjustment points

you 're right , the first idea was to make a network least-squares analysis , but I'd try to do it manually and not by program , the first time , then a comparison between results.

We have a program called Leica SATSA , which comes without any operating maual or explanation of what kind of action is taken. In analyzing the content of gsi file recorded by the program, we can see that the information stored are the horizontal and vertical angles , slope and PPM or prism constant .

Then I have no information on how to perform the analysis manually or whether the stored information is correct or expected ..

I would like to know the methodology , hopefully step by step information for field points and then discuss possible corrections . For example, if I should take more than one measurement per point but with Leica , only SATSA program to measure the same point with the same ID more than once per job .

Thank you ..

 
Posted : January 6, 2014 10:54 am
(@martin-f)
Posts: 219
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Network adjustment points

I have no experience with network analysis software but plenty of folks here have. The more details of the project you provide, the more willing and able folks are to help.
I've never heard of SATSA -- anyone else?

There was a related discussion [msg=183644]Leica VIVA Sets of Angles vs Traverse[/msg], a year ago, which should be worth reading.

 
Posted : January 6, 2014 12:38 pm