We keep a collapsible mearing stick in the S6 case...I think it does a better job than a tape measure. Measuring to prisms with tape allows larger errors there.
In White Rock the third floor (and sometimes forth) at the front of a house would be ground level at the back. There was always plenty of slope in the drainage. We were more concerned with trapping busts than misclosure errors.
A few months back somebody posted about using a blue and a red screw driver for turning points, at each setup, and thus avoiding making the trip twice.
Norman Oklahoma, post: 347016, member: 9981 wrote: What is your (best guess at) the measure up error +/- at the instrument when performing a 3d traverse or topographic surveying?
I read the tape, estimate to the nearest 0.001' and then cut 0.010 for the HI. I think I'm probably getting within 0.005' that way.
I use a 6' folding ruler for measure ups because I think it does a better job than a tape, especiially in the wind.
The test would be remeasuring after you have forgotten what the first number was and seeing if you get the same thing, or measuring in metric and converting. It's repeatable accuracy we are looking for, not just least count precision.
with an S6 I believe it is accurate to +/- 1 mm. There is a notch on the lower part of the instrument and it does the corrections. We have a rotatable optical plummet with the same notch, and our prisms are 0.042 m above that at normal tripod height. None of our tribrachs have built in optical plummets, so all of our setups are either with the S6 or the optical plummet attachment.
This comes up about once a year.
Are you applying temperatute corrections to your measuring tape?
Scott Zelenak has a Wild rod made just for this purpose. It's bent and calibrated to go around the instrument and comes with a table for temperature corrections.
I think if your splitting hundreths on elevations with a Total Station, you're using the wrong tool.
Dallas Morlan, post: 347051, member: 6020 wrote: I know of one organization that requires all such measurements, total station or GPS, to be made in both decimal feet and metric. Both measurements are recorded on a standard form as well as the one entry into the data collector. This has saved them returning to the field a number of times. In addition the office procedures are to convert the metric and compare it to the decimal foot entry on the form and in the data collector.
Same organization documents every recovered original survey or boundary monument with a photo. The photo includes a folding engineering scale and white board with date, corner location and description of physical monument. Same description is included in a field book and coded into the data collector. They believe in redundancy in all phases of survey work. If you are following their work and ask for information you get a digital copy of everything and SP coordinates of the corner(s).
I had guys many years ago who would measure in feet, then convert to meters and write both on the log sheet (GPS). I figured it out when the readings all agreed to the 0.001'. They had no idea WHY they were measuring in both units.
Norman Oklahoma, post: 347100, member: 9981 wrote: The test would be remeasuring after you have forgotten what the first number was and seeing if you get the same thing, or measuring in metric and converting. It's repeatable accuracy we are looking for, not just least count precision.
I'm talking about procedure for engineering design topo, not precise leveling. A couple of hundredths one way or the other isn't going to matter. And l always check to a known point as a blunder check.
The reason I read to the nearest 0.001' is because it's easy to do and there's no point in throwing more error when I don't have to.
For control work I use the special Leica measure up tape, once at set up and again at boxing. Typically the check measurement is within 1 mm, including when done by another with a different tape.
When I started using the special tape I would give it a dummy check by measuring in the regular manner, diff. was typ. less than .015'.
prisms are hard to measure to accurately, but all of our prism/adapters are the same, so forced centering preserves the relationship between HI and HT, where HI can be accurately measured
I do this on GNSS setups. I measure the slant height to the nearest millimeter and the nearest 0.005'. I then enter it into the controller 1.500m and hit enter and get the conversion to compare to my notes.
We started doing it on conventional but found for some reason it caused more mistakes than it caught. I'm not sure why. So for conventional I only measure it in feet.
My standard measure up is 5.3' 2 (28.090) + .32 (.090)=28.18 ö?=5.3085
I usually round off to 0.01'
"What is your (best guess at) the measure up error +/- at the instrument when performing a 3d traverse or topographic surveying?"
If you're including forgetting the measurement, and then forgetting to write it down in the field book immediately, and then winging it when you put it in the data collector with a note that it's wrong in the field book and to measure it again before you traverse on and then forget to do that.....well, .1' covers most situations; for the other dyslexic situations (was that 5.38 or 5.83?), I move it up to .5'. Then I use 1.0' in Starnet.:-D
Those kinds aren't really errors in the statistical sense, but rather they are "blunders". It's a scientific term. It happens all the time in survey work.
I use 0.002m and that is probably generous since I use the Leica height hook and force center any traversing, pretty easy with the Leica height hook to get repeat readings to 0.001 m. This device allows true vertical readings that you add a constant offset to to get to the tilting axis, I use the same tapes for GPS setups and traversing. I also use a fixed height 2.000 m pole, which seems to be 2.000 m and agrees well with tripod setups and usually only use an adjustable height pole for topo, but you can get pretty good heights using the graduations on the Leica pole too, I would guess less than the same 0.002 m.
SHG
Why measure up? HI is irrelevant when you BS the BM and FS using the same rod.
linebender, post: 347163, member: 449 wrote: HI is irrelevant when you BS the BM and FS using the same rod.
Not when you use your control points in the terrain model.
That applies to levelling with a total station and not so much to 3d traversing or topographic mapping.
Not sure why the height hook hasn't caught on with other manufacturers. It definitely improves the measure up precision dramatically.
