Activity Feed › Discussion Forums › Strictly Surveying › Store and reorient a backsight
Store and reorient a backsight
Posted by cole on January 17, 2020 at 3:22 pmwhat exactley does this do? i have used it two ways:
1-when my TS goes out of level, i re-level, go to measure>check>BS check>then store and reorient.
2- TS is not out of level but ive been staking for a couple hours so i store and reorient a new BS
are these both ok? i would think if you use the trunion screws to re level, you are moving the location of the station and everything thereafter would be different than what you staked previously.
nobody at my company seems to know
thanks
Steinhoff replied 3 years, 11 months ago 8 Members · 10 Replies- 10 Replies
I guess it would depend on just how far out of level you have gone. If the legs have been bumped, then you are in a new position.
But for a simple tune up and reorientation – think of your instrument position as being the the tribrach. You have made an effort to center said tribrach over a known point and measured the vertical distance from it. But your instrument position is in the tribrach. Simply relevelling the tribrach by the screws doesn’t change the tribrach’s horizontal position at all. And in most all cases it doesn’t change the height of the instrument by an amount that can be detected by the usual measuring up device – a 25′ box tape.
The movement that causes your instrument to drift off zero are microscopic in nature. Small stresses in the tripod legs, thermal expansion/contraction, etc. Things that can’t be seen with the eye even under the moderate magnification of the optic plumb.
Store and reorient will “re-zero” the horizontal circle (if your survey style is “set BS circle to zero”) or correct the azimuth (if your survey style is “set azimuth”).
When you do this, because the orientation of your instrument has changed, naturally it will change the location of stakeout points compared to before you re-oriented.
Depending on how much out of tolerance your BS check was, and/or how much your instrument has moved since the first setup, the difference may be large enough to see visually, or small enough to be lost within the normal propagated error from setup/measurement. It is up to the operator to decide what is allowable and whether previously set points need to be re-staked.
Most field software help files will tell you what is going on when you perform such a function.
“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil PostmanThis is the remote benchmark (Carlson) operation isn’t it?
I think it is Trimble Access, at least judging by the terminology.
Remote BM in Carlson is similar to Station Elevation in Access, and it only obtains a station HI from a point of known elevation – unless the procedure has changed it does not re-orient the instrument.
“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil PostmanI do not like any procedure that places a new point number on my backsite every time I check it and reshoot it.
Had a PC that would use good procedures apart from recording a new backsite number every time he would check it. That meant having dozens of point numbers with locations being within the area of the end of a matchstick. It was absurd for that to happen.
When I check into my backsite, I look at the horizontal angle readout and if outside what is tolerance for what I am locating next, I simply zero the gun and carry on without shooting anything or making any record other than zeroing the gun, which shows up in the raw data file.
I wanted to revive this thread because I thought the original question was very applicable but I still do not understand some of the comments after the question asked. Can anyone else provide field examples of how store/reorientation works?
- Posted by: @Rover83
Store and reorient will “re-zero” the horizontal circle (if your survey style is “set BS circle to zero”) or correct the azimuth (if your survey style is “set azimuth”).
When you do this, because the orientation of your instrument has changed, naturally it will change the location of stakeout points compared to before you re-oriented.
Depending on how much out of tolerance your BS check was, and/or how much your instrument has moved since the first setup, the difference may be large enough to see visually, or small enough to be lost within the normal propagated error from setup/measurement. It is up to the operator to decide what is allowable and whether previously set points need to be re-staked.
Most field software help files will tell you what is going on when you perform such a function.
When I posted the above up-thread, I included a link to the Trimble help site, which has the following explanation (emphasis mine):
If the point is out of tolerance, you can Store as check, or Store and reorient. Store and reorient will store another observation that will provide a new orientation for subsequent points measured in the current station setup. In a multiple backsight station setup (station setup plus or resection), a check backsight measurement checks the first backsight. Storing and reorienting effectively changes the multiple backsight station setup into a single station setup.
I am confused by the confusion. Is periodically checking the instrument and re-setting zero no longer practiced by field crews?
“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil Postman - Posted by: @rover83
Storing and reorienting effectively changes the multiple backsight station setup into a single station setup.
I am confused by the confusion. Is periodically checking the instrument and re-setting zero no longer practiced by field crews?
It is on my crews. What in cornbread hell is a multiple backsight station setup?
- Posted by: @ansan12001
Can anyone else provide field examples of how store/reorientation works?
Perhaps you are expecting something more complicated than it is. You set zero (or azimuth) on the BS and go to work. After a while you check the BS and find that no longer measures zero. Reorientation just resets that angle back to zero.
Experience teaches us that the backsight check will never equal exactly zero. I find that reorientation is needed after being set up about 20 minutes. After that the drift will be minimal – but never nothing at all. In most staking circumstances checking the backsight after every shot is impractical, and unnecessary for ordinary work. How often you should do it depends on your equipment, the site conditions, and the needs of the project at hand.
For high precision work, such as control or boundary ties, typical practice is to turn sets which among other thing has the backsight and foresight being recorded in quick succession.
In regards to Trimble equipment, a multiple backsight station setup is the “station setup plus” function, where multiple points are sighted to attempt to correct orientation errors (network control, mostly). See below for a link that explains it better than I would.
Log in to reply.