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Measure Up Error
What is your (best guess at) the measure up error +/- at the instrument when performing a 3d traverse or topographic surveying?
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42 Replies
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I’m thinking <.02' (if I'm reading the question correctly)
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I think you are reading it correctly. My guess, stated in statistical terms, would be a standard deviation of +/-0.01′, which implies a 95% confidence of about +/- 0.02′ if it is done as well as it can be done using the ordinary method.
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5mm
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I measured our TCRA1203+ (the S6 is still in the field but I assume it’s close enough to the same). It has a radius of 4″.
Therefore:
Measured HI, True HI, Delta
4.00, 3.99, 0.01
4.50,4.49,0.01
5.00,4.99,0.01
5.50,5.49,0.01
6.00,5.99,0.01So it looks like about 0.01′.
I use the bottom notch on the S6 which is corrected to vertical by the Access software.
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I use 0.015. I think we are all in the same ball game.
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Dave Karoly, post: 347028, member: 94 wrote: …So it looks like about 0.01′ …
That is assuming your instrument personnel can successfully read a Lufkin tape accurately AND consistently.
My guys all swear they can, but I can show you a lot of evidence to the contrary.
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That would be the systematic error for “slope”. I’m thinking more of the random error of the actual taping to whatever mark you use.
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I grant you that. There is some uncertainty which should add to my mathematics.
Also looking at the Leica reminded me of its ergonomic problem of having knobs stick out which makes it impossible to lay the tape right on the dot. So there is a little guessing about which hundredth we are on.
The S6 is a lot better with the bottom notch but even then I have to hold the tape then try to look through the reading part of my glasses so that can add to uncertainty.
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That would be 0.016′ for those of you in Rio Linda.
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Tough to keep the tape straight when doing the measure up in a tornado.
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Rio Linda is a funny place.
There will be a McMansion on 5 acres in a walled compound next to a guy with a trailer and cars on blocks :-).
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s.e. = +/- 0.005 ft. for a slant height measured with a tape.
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If your gonna decimalise the foot you might as well just use metric. Like us more advanced nations.:-D
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Or is it decimalize in your case
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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).
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An outfit I worked for in White Rock, B.C. would have us run levels that way. Read both the metric and imperial side of the rod. White Rock is built on a bluff overlooking the Pacific Ocean, and level runs were typically very steep. So we only ran one way, and the double readings were the check.
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Norman Oklahoma, post: 347054, member: 9981 wrote: An outfit I worked for in White Rock, B.C. would have us run levels that way. Read both the metric and imperial side of the rod. White Rock is built on a bluff overlooking the Pacific Ocean, and level runs were typically very steep. So we only ran one way, and the double readings were the check.
About 1995 when I was with the Highway Dept. and we got new digital levels. Just for a “safety net” I also ran standard spirit levels with the instruments fairly close to each other on the same TBMs and kept the notes in a separate book. While I did this just to make myself feel better about the “new fangled” digital level, when we got to the end I realized I already had the notes for the “return run”!
BTW – We were able to determine a few human errors in the spirit level run with the digital data. Made a believer out of me.
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I use 0.01′ error setting in StarNet and things usually work. Sometimes I can dial it down to 0.005′. But not very often.
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We could say that it was 16 thousandths. Or 16 millifoots (millifeet?). Do you enter the measure up to your dc software as a whole number in millimeters?
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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.
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