Beware Checkshots

Discussion of FieldGenius related issues and questions.

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Beware Checkshots

Postby bobL » Mon Jan 16, 2006 8:22 am

For those still using FG 2005, when using the checkshot routine the program averages the original shot and the check shots together and adjusts the stored point automatically. We recently discoverd this by accident when checking some data on a large traverse we did. We shot a point, then shot it again 2000 ft later, the program averaged them together without us knowing. Fortunately the difference between the points was only .18', so the overall closure wasn't really affected. Had this been a 2 or 3 foot difference in the two points, we would have been scratching our heads for a long time.
bobL
 
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Check Point routine

Postby Glen Cameron » Mon Jan 16, 2006 9:40 am

The Check Point routine gives you the option to Store the Point, or not store it by simply picking OK. If you Store it then it is a side shot and will be averaged. If you simply pick OK then it is not used in the calculation of that point, it is simply stored as a comment in the raw file

The comments would look something like this in the raw file:

-- Check Point ID: 1
-- Check Point dNorthing: 0.09'
-- Check Point dEasting: -0.18'
-- Check Point dElevation: 0.00'

If you store the point then it asks if it is a SS (sideshot) or TR (traverse) point.

Cheers,
Glen W. Cameron, C.E.T.
City of North Bay, Ontario
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Checkpoint

Postby bobL » Mon Jan 16, 2006 10:21 am

1. Why would you want to average a checkshot into a traverse?

2. Nowhere in the manual does it mention the check point being averaged when stored as a sideshot.

If your going to have a point recorded during a checkshot, fix it so that the point is recorded separately and NOT averaged together with the existing point.
Some people might use checkpoints to average a house tie or a fence shot but I think most people would use it when checking into a control pt on a traverse. Can you not see this becoming a large problem if one of the two shots were taken incorrectly? It's a pitfall that you'd spend hours trying to figure out!!
bobL
 
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Joined: Tue Dec 17, 2002 2:26 pm

Check Shot

Postby Glen Cameron » Mon Jan 16, 2006 11:44 am

If the Check Shot is recorded then it is treated the same as any other side shot. You can apply a different point number to the shot if desired.

Some people use the check shot routine to collect data that is used in adjustments like Least Squares. We do not control what people wish to use the option for - we simply add it to the program when we have people ask for it.

You can choose not to record it, so you do not have it doing anything to your data, if desired, or you can record it with a different point number. If you use the same point number then it will be treated like all other sideshots and used appropriately.

Cheers,
Last edited by Glen Cameron on Tue Jan 24, 2006 7:36 am, edited 1 time in total.
Glen W. Cameron, C.E.T.
City of North Bay, Ontario
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Postby Jason Poitras » Mon Jan 23, 2006 11:27 am

Hello,

Glen is correct and I want to make it clear that the check shot routine does not over write the point your checking, and that if the user decides to store the shot, a different point number is automatically used.
Jason Poitras
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