Collecting data using a Leica TCP1201+ and a Leica CS15 Data Collector. The total station is set up using a three point resection and is accidentally bumped to where it is no longer leveled and you receive a message on the data collector saying so.
Best Practices -
Readjust the leveling on the total station and continue?
Readjust the leveling and perform the resection again and then continue?
Hopefull you had set a hub at your resection setup.
Then you simply start a new setup with current set5ings.
DaveJay, post: 452068, member: 12592 wrote: Collecting data using a Leica TCP1201+ and a Leica CS15 Data Collector. The total station is set up using a three point resection and is accidentally bumped to where it is no longer leveled and you receive a message on the data collector saying so.
Best Practices -
Readjust the leveling on the total station and continue?
Readjust the leveling and perform the resection again and then continue?
Perform the resection again.Don't carry on as your instrument has moved in position - and worse - orientation.
It doesn't just move out of level without the top of the tripod moving as well.
I don't tend to put hubs (pegs) in for resection setups as they are not generally in places that they will have any life expectancy (civil construction site). Occasionally I will put the instrument in the box and leave the tribrach on the tripod for a short while. If the instrument is level after clipping it back in I assume that the tripod has been undisturbed and just take a backsight to one station.
Also there is a small gain using the resection method of eliminating the horizontal and vertical centring errors of setting up over a station.
I can see the attraction of doing so though ie repeatability. But I put my faith in a multipoint resection mostly.
I use retro targets and semi-permanent prisms and spigots for control on these sites.
A Harris, post: 452069, member: 81 wrote: Hopefull you had set a hub at your resection setup.
Then you simply start a new setup with current set5ings.
I generally do not set a hub at the location of the total station when I do a resection.
squowse, post: 452074, member: 7109 wrote: Perform the resection again.Don't carry on as your instrument has moved in position - and worse - orientation.
It doesn't just move out of level without the top of the tripod moving as well.I don't tend to put hubs (pegs) in for resection setups as they are not generally in places that they will have any life expectancy (civil construction site). Occasionally I will put the instrument in the box and leave the tribrach on the tripod for a short while. If the instrument is level after clipping it back in I assume that the tripod has been undisturbed and just take a backsight to one station.
Also there is a small gain using the resection method of eliminating the horizontal and vertical centring errors of setting up over a station.
I can see the attraction of doing so though ie repeatability. But I put my faith in a multipoint resection mostly.I use retro targets and semi-permanent prisms and spigots for control on these sites.
This makes the most sense to me. I've gotten conflicting information on this subject but personally I would redo the resection before carrying on. Thanks.
Re-level and re-resect.
squowse, post: 452074, member: 7109 wrote: Perform the resection again.Don't carry on as your instrument has moved in position - and worse - orientation.
It doesn't just move out of level without the top of the tripod moving as well.I don't tend to put hubs (pegs) in for resection setups as they are not generally in places that they will have any life expectancy (civil construction site). Occasionally I will put the instrument in the box and leave the tribrach on the tripod for a short while. If the instrument is level after clipping it back in I assume that the tripod has been undisturbed and just take a backsight to one station.
Also there is a small gain using the resection method of eliminating the horizontal and vertical centring errors of setting up over a station.
I can see the attraction of doing so though ie repeatability. But I put my faith in a multipoint resection mostly.I use retro targets and semi-permanent prisms and spigots for control on these sites.
I fired a guy who would do nothing but resections without setting over points. I don't care if it will not survive, what if there is a mishap and you need to verify the point? The stale or nail is less expensive than not being able to check the point later.
I'm curious how you would verify the point if it was destroyed?
A Harris, post: 452116, member: 81 wrote: [USER=7109]@squowse[/USER]
raw data
notes in field book
Yes, sorry for the rhetorical question - that is how I would do it, but Spledeus seemed to be saying he wanted a nail even if it wouldn't survive. I think he meant that you may as well put it in, in case it survives long enough to do a check on later. For me, sometimes a disturbed station is worse than no station at all?
Need to have verifiable stations in the ground or other fixed point. But in the useful positions to set up an instrument they don't stay undisturbed very long.on my sites.
Suppose I resection into a point inside a building footer to set corner nails for masons. In a few short days the walls would probably be high enough to prevent a typical backsight to my control, still there is a nail under my instrument. Maybe it is only a 12 penny and not a spike. When I am done I consider if I am coming back to it and may pull it t end of day, but it is there as long as the instrument is. I have tripped over enough tripod legs to know that it can and will happen no matter how conscious I am.
Paul in PA
Paul in PA, post: 452122, member: 236 wrote: Suppose I resection into a point inside a building footer to set corner nails for masons. In a few short days the walls would probably be high enough to prevent a typical backsight to my control, still there is a nail under my instrument. Maybe it is only a 12 penny and not a spike. When I am done I consider if I am coming back to it and may pull it t end of day, but it is there as long as the instrument is. I have tripped over enough tripod legs to know that it can and will happen no matter how conscious I am.
Paul in PA
Yes that's a good example where you need to think ahead for loss of visibility. Reminds me of getting control set up before the site hoarding (fence) goes up. Have been know to cut peep holes and remove panels as a last resort.
I mostly work on large civil sites these days so it's a bit different. Everywhere is a machine track. Concrete foundations get buried. The only alternative to resection on temporary stations is to traverse in each time.
A nail under the instrument is a bit of a check I suppose but I rely on the level if I am honest. I don't see it being possible to disturb the instrument without putting it out of level. I suppose someone might "help" you by levelling it up again after knocking it?
I tend not to leave the instrument out when I'm not within sight of it.
Re-level and resection. I generally don't set anything under a resection because the tape measure up pollutes the pure trig level data and propagates forward. If I do set something under the resection I note it as not to be trusted for elevation until observed from another HI=0.00 resection setup or two. I also rely on the level -- if it hasn't moved, neither has the instrument. If the bubble has moved -- re-level and new resection.
I've started putting a nail under resection stations so that I can use them as backsights. I often resect in using Integrated Surveying and then turn direct and reverse to a foresight when I'm ready to move ahead.
Lee D, post: 452137, member: 7971 wrote: I've started putting a nail under resection stations so that I can use them as backsights. I often resect in using Integrated Surveying and then turn direct and reverse to a foresight when I'm ready to move ahead.
I would generally leave the tripod behind with a prism on and take the instrument forward with another tripod and tribrach. Less walking back and forth.
It certainly doesn't hurt to stick a nail in the ground though. I do do it under certain circumstances. I am just struggling to think of them.
DaveJay, post: 452068, member: 12592 wrote: Best Practices -
Readjust the leveling on the total station and continue?
Readjust the leveling and perform the resection again and then continue?
As always: it depends.
If your definition of "Best Practices" is something like: commercial or professional procedures that are accepted or prescribed as being correct or most effective. Then you have to factor in what the data is being collected for, how badly the gun was bumped, and how far away from the gun are your remaining shots - it may be most effective (and well within your error budget) to simply relevel and carry on.
You can check the anticipated error after releveling and then reshooting a previously shot point (one further from the gun) - the inverse between the old shot and new shot is representative of your error at that distance. Unless the gun was bumped hard, there probably won't be measurable vertical error (less than 0.01'). Horizontal error will be more varied depending on how the gun was disturbed. If this takes less time than resectioning then it's worth doing.
If you don't have staff that can reliably assess whether or not the data will meet spatial validity requirements then your policy for this situation has to be that the crew will always need to spend the time to "Readjust the leveling and perform the resection again and then continue".
If rocking out of level is a problem in your work perhaps it is time to check that your legs are in good adjustment and your procedure for setting up a tripod is sound. I would consider moving the instrument to another position all together if those two variables were in control and I was still falling out.
Of course if the tripod has settled you need to re-verify its position.
I have performed thousands of resections without setting a point below the tripod. In underground work it is the only practical approach.
spledeus, post: 452110, member: 3579 wrote: I fired a guy who would do nothing but resections without setting over points. I don't care if it will not survive, what if there is a mishap and you need to verify the point? The stale or nail is less expensive than not being able to check the point later.
Amen, Amen, Amen
Seems to be a divisive subject!
Over 15 years ago we spent a lot of time on construction jobs trying to protect and check stations round the edges of the site, and also on temporary points inside the site. It was a very frustrating and time consuming process. I don't believe the accuracy or verifiability (if that's a word) was anywhere near as good as current methods. Need to trust in the equipment and check the raw observation files on the logger for QC.
One never knows when you just might need that point you've resected over and if it's only spatial and not a real mark then it's lost for any further use.
I make a habit of even just putting a springhead nail under.
Proved beneficial enough to warrant the couple of minutes it takes.
That's my preferred way. Wouldn't castergate others for not doing such.
