Community Forums

Share:

Station Elevation for control points  


cole
Posts: 19
 cole
Member
(@cole)
5+ posts
Joined: 5 months ago

so, something ive been doing is setting up a job with GPS by taking two shots really far apart, (scope of site) then setting a point in the middle that i can occupy with the total station which can see the other two GPS shots, holding one of the GPS elevation, and then station elevation my robot to the point in the middle. this reduces the vert deltas i get using GPS ie: usually my GPS shots can be up to .1  delta ,when using the total station and station elevating i can get them much closer together (like.02)  

 

the problem, when you do a station el it only allows me to either discard or store another. so i click store another, but then in my point manager it shows multiple points with the same # and they have diff coords. this worries me bc how do i know which point # is going to be used for station setups next time i occupy ??

 

can someone please explain what a station elevation really does and what its appropriate use is?

 

thank you,

 

cole

4 Replies
Bill93
Posts: 5685
Member
(@bill93)
5,000+ posts
Joined: 9 years ago

This appears to be a software specific issue, and most will handle things differently, so you aren't going to get much help until you tell what you are running.

Reply
SW_Surveyor
Posts: 2
Member
(@sw_surveyor)
FNG
Joined: 2 years ago

Terminology used sounds like it’s Trimble Access software. Are you sure the multiple coordinates for the same point name aren’t the different face 1 and face 2 observations? 

Reply
Mark Mayer
Posts: 2712
Member
(@mark-mayer)
2,500+ posts
Joined: 9 years ago

I recommend that you, first, set 3 or 4 points with the GPS rather than just 2. Then use all such points and the resection routine to determine your TS location and orientation.  This amounts to a least squares adjustment of the TS position and elevation, best fitting to all of the GPS positions.

If you wish to carry things further you can reshoot the GPS mons with the TS to get positions for them relative to the adjusted TS location. Or, if you have some sort of software available to you to recalc coordinates from raw data, you can repurpose your resection ties to that use back at the office. 

I regularly do just this myself and use StarNet to simultaneously adjust the GPS vectors and TS measurements.      

Reply
1 Reply
Rover83
Member
(@rover83)
Joined: 4 years ago

100+ posts
Posts: 117
Posted by: @mark-mayer

I recommend that you, first, set 3 or 4 points with the GPS rather than just 2. Then use all such points and the resection routine to determine your TS location and orientation.  This amounts to a least squares adjustment of the TS position and elevation, best fitting to all of the GPS positions.

Mark has the right workflow for this situation. Resection from at least 3 points to get a better solution.

A resection will perform the same routine as Station Elevation, as well as a best-fit solution for horizontal values too. In other words, just do a resection, and if you are sitting on a point be sure to enter your instrument height.

 

Regarding the Station Elevation routine in Access (assuming this is what you are describing) - this overwrites the grid elevation of the existing point. It does not change horizontal positions. Look at the hierarchy symbols in your Point Manager to see which position is being held - the vertical will be coming from that station elevation routine.

Besides, if you are merely gathering observations and will be post-processing (i.e. you are not staking or setting anything in the field), there's no need to worry about which observation is being held in the field, unless you are seeing major discrepancies in check shots. Those "store as check" observations will be very close to the held position, which should be sorted out in the post-processing and QA/QC workflow anyways.

Reply
Default
:)
:d
:wink:
:mrgreen:
:neutral:
:twisted:
:arrow:
:shock:
:???:
:cool:
:evil:
:oops:
:razz:
:roll:
:cry:
:eek:
:lol:
:mad:
:sad:
:!:
:?:
:idea:
:hmm:
:beg:
:whew:
:chuckle:
:silly:
:envy:
:shutmouth: