Dan Henry, post: 441869, member: 10756 wrote: Yes, this is our next move.
I'll be very interested to hear the conclusion of this story. A maladjusted tribrach is easy to detect, but something within the instrument, maybe not so much. My money remains on some condition external to the instrument being the culprit.
Maybe there's a loose nut behind the eyepiece.
Dave Lindell, post: 441968, member: 55 wrote: Maybe there's a loose nut behind the eyepiece.
Actually, a loose reticle came to mind. It's not the sort of problem that would just spontaneously appear, but, if it did, would probably introduce the sort of errors complained of.
Unless you have a pole with a very fine bubble in it, it seems hard to get good closure. Tribrachs on a tripod give better results. Is the rodman using a bipod at least. If its a two man crew, how is the back siight setup. Pole and bipod? I know you can get good closure with a pole but that might be what I'd be looking at for the problem.
Kent McMillan, post: 441969, member: 3 wrote: Actually, a loose reticle came to mind. It's not the sort of problem that would just spontaneously appear, but, if it did, would probably introduce the sort of errors complained of.
I will check for that. Good thought.
Dan Henry, post: 441460, member: 10756 wrote: Hi all,
We have one crew that for the past several months has consistently come back with traverses that have double the allowable angular error.
The instrument is a Topcon ES 100 series, only a few months old and freshly calibrated. The crew chief has over 30 years experience and the rodman has nearly as much. We've spent considerable resources checking every conceivable component that could be causing this. Daily rod plumb checks, swapped instrument out with other instruments known to generate good closures, replaced tripod legs with brand new, verified plummet is calibrated. basically everything we could think of. The distances check great, and the sets direct/reverse resolve within allowable tolerances, and yet still the overall traverse loop will be significantly over allowable angular on a regular basis.
What are we missing?
Dan
I'd bet a hundred dollar bill, without looking at the rest of the responses, that the instrument needs to be re-collminated. It's in the back of the book. The dead ringer for when it is necessary is when you level the gun up, roll the barrel up and down and see if the horizontal angle changes. If it does, it needs to be adjusted by the method in the manual. You won't notice it too terribly much until you start running in the hills or you have a really flat traverse except for one backsight down the hill and one up the hill and the rest level. It will mess with your head.
It's an intertive process for me or to say it typically takes a few times. We do it enough we remember it and if we notice it happening in the field we adjust it right there.
David Livingstone, post: 442006, member: 431 wrote: Unless you have a pole with a very fine bubble in it, it seems hard to get good closure. Tribrachs on a tripod give better results. Is the rodman using a bipod at least. If its a two man crew, how is the back siight setup. Pole and bipod? I know you can get good closure with a pole but that might be what I'd be looking at for the problem.
Bipods on both fore and back sights. They stack the backsight with the bipod, rodman moves ahead and sets ahead with second rod/bipod, and sets are made to both as set. Sets are shot BD, FD, FR, BD with a fresh level, centering, and zero. When they return to the backsight to move it up, they check to make sure it's still plumb and re-do the set if it wasn't.
We've run traverses with rod/bipod for years and usually get good results. AS I understand it, equipment was swapped around this morning, so we'll see what happens next.
Kris Morgan, post: 442011, member: 29 wrote: I'd bet a hundred dollar bill, without looking at the rest of the responses, that the instrument needs to be re-collminated. It's in the back of the book. The dead ringer for when it is necessary is when you level the gun up, roll the barrel up and down and see if the horizontal angle changes. If it does, it needs to be adjusted by the method in the manual. You won't notice it too terribly much until you start running in the hills or you have a really flat traverse except for one backsight down the hill and one up the hill and the rest level. It will mess with your head.
It's an intertive process for me or to say it typically takes a few times. We do it enough we remember it and if we notice it happening in the field we adjust it right there.
Slight hi-jack.
Kris - It's been awhile....but the collumination routines DO NOT physically adjust the error. They simply measure the error and adjust the angular readout accordingly. The horizontal angle SHOULD change as you tilt the vertical axis up to reflect the physical tilt axis error. Zero the gun sighting a plumb line, then turn a steep angle. The crosshairs will be slightly off plumb (and the horizontal angle should reflect this). Sight the plumb line at that steep angle and the horizontal angle should return to near zero. The instrument would either have to be in perfect physical adjustment or the collumination turned off in order for the horizontal angle not to change as you adjust the vertical angle.
Maybe you have an instrument where it is possible to physically adjust the tilt axis error?
Dan Henry, post: 442013, member: 10756 wrote: Bipods on both fore and back sights. They stack the backsight with the bipod, rodman moves ahead and sets ahead with second rod/bipod, and sets are made to both as set. Sets are shot BD, FD, FR, BD with a fresh level, centering, and zero. When they return to the backsight to move it up, they check to make sure it's still plumb and re-do the set if it wasn't.
We've run traverses with rod/bipod for years and usually get good results. AS I understand it, equipment was swapped around this morning, so we'll see what happens next.
If I was having issues with angular errors, I'd be ditching the bi-pod sights and using 3 tripods until I had it figured out.
imaudigger, post: 442034, member: 7286 wrote: Slight hi-jack.
Kris - It's been awhile....but the collumination routines DO NOT physically adjust the error. They simply measure the error and adjust the angular readout accordingly. The horizontal angle SHOULD change as you tilt the vertical axis up to reflect the physical tilt axis error. Zero the gun sighting a plumb line, then turn a steep angle. The crosshairs will be slightly off plumb (and the horizontal angle should reflect this). Sight the plumb line at that steep angle and the horizontal angle should return to near zero. The instrument would either have to be in perfect physical adjustment or the collumination turned off in order for the horizontal angle not to change as you adjust the vertical angle.Maybe you have an instrument where it is possible to physically adjust the tilt axis error?
All I'm saying is you can't close a set of angles when this is going on. Once in adjustment, it doesn't move and the angles work better. Sun shots are impossible when it's out.
Kris Morgan, post: 442011, member: 29 wrote: I'd bet a hundred dollar bill, without looking at the rest of the responses, that the instrument needs to be re-collminated. It's in the back of the book. The dead ringer for when it is necessary is when you level the gun up, roll the barrel up and down and see if the horizontal angle changes. If it does, it needs to be adjusted by the method in the manual. You won't notice it too terribly much until you start running in the hills or you have a really flat traverse except for one backsight down the hill and one up the hill and the rest level. It will mess with your head.
It's an intertive process for me or to say it typically takes a few times. We do it enough we remember it and if we notice it happening in the field we adjust it right there.
Kris, you are correct. For some reason that series instrument won't hold collimation long. The routine in the manual will reset those values.
Dan Henry, post: 441460, member: 10756 wrote: Hi all,
We have one crew that for the past several months has consistently come back with traverses that have double the allowable angular error.
The instrument is a Topcon ES 100 series, only a few months old and freshly calibrated. The crew chief has over 30 years experience and the rodman has nearly as much. We've spent considerable resources checking every conceivable component that could be causing this. Daily rod plumb checks, swapped instrument out with other instruments known to generate good closures, replaced tripod legs with brand new, verified plummet is calibrated. basically everything we could think of. The distances check great, and the sets direct/reverse resolve within allowable tolerances, and yet still the overall traverse loop will be significantly over allowable angular on a regular basis.
What are we missing?
Dan
Several years ago, I was using a new Topcon robot. I forget the exact model, maybe some version of the 8200. We would get bad angles every so often. Drove us nuts for a week or two until we noticed that on (apparently random) occasion, when we flipped the scope and lined up on the backsight, the reading would jump exactly 4 minutes.
Sent the instrument in to have it checked. The explanation came back as a bad hardware component.
Both I and the guy I was working with had about 25 years of experience at the time.
My two cents:
Back in the days of theodolites, T-16, T-2 for me, for turning sets of angles, my first real party chief, Jimmy Boyd, taught me to always turn on to each target from the same direction. What he understood was that there was systematic error in the tangent screws that could be a problem. Made sense to me, so I always used that method.
He said to pick a direction (left or right) and always gain that target from that direction. No fine tuning back and forth across the target when you get there. Come in from the right, and if you pass the target, go back beyond it and come on to it from the right. He was always the guy with the tightest angle sets of anyone I worked with.
That and clicking the chain were two things that stuck with me and served me well for many years.
JA, PLS SoCal
Jerry Attrick, post: 442323, member: 1585 wrote: My two cents:
Back in the days of theodolites, T-16, T-2 for me, for turning sets of angles, my first real party chief, Jimmy Boyd, taught me to always turn on to each target from the same direction. What he understood was that there was systematic error in the tangent screws that could be a problem. Made sense to me, so I always used that method.
He said to pick a direction (left or right) and always gain that target from that direction. No fine tuning back and forth across the target when you get there. Come in from the right, and if you pass the target, go back beyond it and come on to it from the right. He was always the guy with the tightest angle sets of anyone I worked with.
That and clicking the chain were two things that stuck with me and served me well for many years.
JA, PLS SoCal
You should do the same with an EDM. Always use the same set of electronic trigger marks.
I finish up with a clockwise turn on the adjustment knob with a light touch of the thumb.
Paul in PA
Jerry Attrick, post: 442323, member: 1585 wrote: clicking the chain
?????
Jerry Attrick, post: 442323, member: 1585 wrote: My two cents:
Back in the days of theodolites, T-16, T-2 for me, for turning sets of angles, my first real party chief, Jimmy Boyd, taught me to always turn on to each target from the same direction. What he understood was that there was systematic error in the tangent screws that could be a problem. Made sense to me, so I always used that method.
He said to pick a direction (left or right) and always gain that target from that direction. No fine tuning back and forth across the target when you get there. Come in from the right, and if you pass the target, go back beyond it and come on to it from the right. He was always the guy with the tightest angle sets of anyone I worked with.
That and clicking the chain were two things that stuck with me and served me well for many years.
JA, PLS SoCal
"Turning angles by turning the fine motion always CW."
I have never found any justification in that practice. If I need back off a micro radian, I back off a micro radian. T1/T2/T3/T16, glass plate, micrometer or not. When averaging sets just beware of an outlier.
Jerry Attrick, post: 442323, member: 1585 wrote: My two cents:
Back in the days of theodolites, T-16, T-2 for me, for turning sets of angles, my first real party chief, Jimmy Boyd, taught me to always turn on to each target from the same direction. What he understood was that there was systematic error in the tangent screws that could be a problem. Made sense to me, so I always used that method.
He said to pick a direction (left or right) and always gain that target from that direction. No fine tuning back and forth across the target when you get there. Come in from the right, and if you pass the target, go back beyond it and come on to it from the right. He was always the guy with the tightest angle sets of anyone I worked with.
That and clicking the chain were two things that stuck with me and served me well for many years.
JA, PLS SoCal
"Turning angles by turning the fine motion always CW."
I have never found any justification in that practice. If I need back off a micro radian, I back off a micro radian. T1/T2/T3/T16, glass plate, micrometer or not. When averaging sets just beware of an outlier.
Larry Scott, post: 442435, member: 8766 wrote: "Turning angles by turning the fine motion always CW."
I have never found any justification in that practice. If I need back off a micro radian, I back off a micro radian. T1/T2/T3/T16, glass plate, micrometer or not. When averaging sets just beware of an outlier.
I think that it originated in a much earlier generation of theodolites that were prone to "jump" as the tangent screw was loosened, hence moving the tangent motion in the direction that compressed the spring was considered best practice. Wasn't this in Bomford? I could cheat and look, but that's my vague recollection.
Kent McMillan, post: 442440, member: 3 wrote: I think that it originated in a much earlier generation of theodolites that were prone to "jump" as the tangent screw was loosened, hence moving the tangent motion in the direction that compressed the spring was considered best practice. Wasn't this in Bomford? I could cheat and look, but that's my vague recollection.
Probably a method to use if the spring tensioner is dirty, or it's very cold, or a David White, old timer Berger.
I just think only CW isn't as objective, and with scintillation, I may wiggle in to where I think the target really is. Always backing off and starting over in heat, I'd never get anything done.
Proper lubes on the motions, (and stick with Wild).
