Trimble Business Center

I recently did a survey with a resection setup to 4 mounted prisms and used the 'compute station elevation' checked on during the setup. After reviewing the data I realize that the setup elevation should be changed by .003m. In the optical spreadsheet I can easily change the setup true height from 1.902 to 1.899, and then compute a network adjustment. The elevation of the resect point changes as expected. But none of the other observations change. 

Am I missing something here, I expected everything to change by .003 ??????
Thanks

TBC 5.70
SX10
TSC5

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ian bissonnette
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From what you describe that seems totally correct to me.
If you perform a resection than everything is "hanging" via the zenith/horizontal angles and slope distances on your control points. The intersection point of all the rotation axiis of your instrument will be derived from those and afterwards, via the "instrument height", that point below your instrument. That's the reason why only that elevation is changing if you change the instrument height.
In order to change the elevation of all measured points you'd have to change the observations to your control points, or the coordinates of them. Only then the intersection point of all the rotation axiis of your instrument will change.

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Ronny Schneider
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Thanks Ronny. Maybe I was not totally clear in my description, sorry. So I did the resection and then realized in the office that my measured true height was wrong, your blue line(thanks for the sketch up). Then I change the true height in the office, and I am happy with the control used for the resection, and happy that the resect point has shifted. But the problem is that all my subsequent observations from the resect point, in this case a bunch of bolt asbuilts and benchmarks set, do not shift in elevation in TBC(that I can see). It is clear in TBC that the angles and distances to these bolt and benchmark shots come from the point bellow the instrument so I would think and hope that these would shift when the true height is changed? Any ideas?
If it is not supposed to work like this and you have to change all the control points to a wrong elevation I would question why you can enter the instrument height at all or why you can change it in TBC.

Thanks for taking the time to think about it.


Original Message:
Sent: 2/4/2023 10:23:00 PM
From: Ronny Schneider
Subject: RE: TBC change in resection setup height not reflected in observations

From what you describe that seems totally correct to me.
If you perform a resection than everything is "hanging" via the zenith/horizontal angles and slope distances on your control points. The intersection point of all the rotation axiis of your instrument will be derived from those and afterwards, via the "instrument height", that point below your instrument. That's the reason why only that elevation is changing if you change the instrument height.
In order to change the elevation of all measured points you'd have to change the observations to your control points, or the coordinates of them. Only then the intersection point of all the rotation axiis of your instrument will change.

------------------------------
Ronny Schneider
------------------------------

The change of the instrument height of this resect point would only influence those subsequent points if you'd have performed an additional station setup on this point, and then shot the subsequent points.

Otherwise this resect point and all the subsequent points of this one station are the results of the resection. This doesn't only work in TBC like this but each and every other adjustment program.

In your case the instrument height actually shouldn't matter, unless you need this point later as control point. And your subsequent points should be fine and shouldn't shift.

------------------------------
Ronny Schneider
------------------------------

Original Message:
Sent: 02-04-2023 21:25
From: ian bissonnette
Subject: TBC change in resection setup height not reflected in observations

Thanks Ronny. Maybe I was not totally clear in my description, sorry. So I did the resection and then realized in the office that my measured true height was wrong, your blue line(thanks for the sketch up). Then I change the true height in the office, and I am happy with the control used for the resection, and happy that the resect point has shifted. But the problem is that all my subsequent observations from the resect point, in this case a bunch of bolt asbuilts and benchmarks set, do not shift in elevation in TBC(that I can see). It is clear in TBC that the angles and distances to these bolt and benchmark shots come from the point bellow the instrument so I would think and hope that these would shift when the true height is changed? Any ideas?
If it is not supposed to work like this and you have to change all the control points to a wrong elevation I would question why you can enter the instrument height at all or why you can change it in TBC.

Thanks for taking the time to think about it.



Original Message:
Sent: 2/4/2023 10:23:00 PM
From: Ronny Schneider
Subject: RE: TBC change in resection setup height not reflected in observations

From what you describe that seems totally correct to me.
If you perform a resection than everything is "hanging" via the zenith/horizontal angles and slope distances on your control points. The intersection point of all the rotation axiis of your instrument will be derived from those and afterwards, via the "instrument height", that point below your instrument. That's the reason why only that elevation is changing if you change the instrument height.
In order to change the elevation of all measured points you'd have to change the observations to your control points, or the coordinates of them. Only then the intersection point of all the rotation axiis of your instrument will change.

------------------------------
Ronny Schneider
------------------------------

thanks ronny. i guess if this is the case it might be good to either whiteout the option to change the true height in tbc or give a warning that this will not alter the subsequent shots. it was certainly not obvious to me what was happening. the other thing that is a little funny. i did a buch of rezero check shots to the backsight (first point of the resection), and these seem to be written in tbc as a new setup, but i guess these don t count as such for this application.

if this is going to stay like this i will make sure to do a new station setup, or more likely resect with a 0 true height(and just record my true height as a check) which is likely what is intended.

can you describe how tbc performs with a station elevation routine done after a resection? are all subsequent shots still fixed in this case or can they be changed if you change the station elevation shot elevation. just curious here.

thanks.


Original Message:
Sent: 2/5/2023 2:55:00 AM
From: Ronny Schneider
Subject: RE: TBC change in resection setup height not reflected in observations

The change of the instrument height of this resect point would only influence those subsequent points if you'd have performed an additional station setup on this point, and then shot the subsequent points.

Otherwise this resect point and all the subsequent points of this one station are the results of the resection. This doesn't only work in TBC like this but each and every other adjustment program.

In your case the instrument height actually shouldn't matter, unless you need this point later as control point. And your subsequent points should be fine and shouldn't shift.

------------------------------
Ronny Schneider
------------------------------


Original Message:
Sent: 02-04-2023 21:25
From: ian bissonnette
Subject: TBC change in resection setup height not reflected in observations

Thanks Ronny. Maybe I was not totally clear in my description, sorry. So I did the resection and then realized in the office that my measured true height was wrong, your blue line(thanks for the sketch up). Then I change the true height in the office, and I am happy with the control used for the resection, and happy that the resect point has shifted. But the problem is that all my subsequent observations from the resect point, in this case a bunch of bolt asbuilts and benchmarks set, do not shift in elevation in TBC(that I can see). It is clear in TBC that the angles and distances to these bolt and benchmark shots come from the point bellow the instrument so I would think and hope that these would shift when the true height is changed? Any ideas?
If it is not supposed to work like this and you have to change all the control points to a wrong elevation I would question why you can enter the instrument height at all or why you can change it in TBC.

Thanks for taking the time to think about it.