I bought a Bosch GLM42 Distance Meter for dipping manholes, at Home Depot.?ÿ I held off doing so because I wasn't sure that it could be set to read in decimal feet. The literature was not conclusive. But I took a shot at it and it does.?ÿ
Then the big bonus - it has a feature to correct slope distance to vertical distance. Again, the literature is silent.?ÿ
Very good for as-builts of dry manholes. Not sure how it will deal with pipes with flow.?ÿ But I just thought I'd pass this along.?ÿ
I recently got a Leica Disto X3. It also corrects for slope. It works great in the office but outside I usually get an error message that the sun is too bright - shade the target. Maybe it will be useful if I measure a manhole sometime.
My old Disto (circa 2003) will measure to the water surface of turd flow accurately.
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Often the results of measuring MH's with a level rod are repeatable to about +/- 0.3' or so. So if the flow is not too great, even to the top of the water surface may be an improvement.
so what's the use of the disto if you can't get to the manhole toe? go back to the good old stick & meter
Two points:
We still have an ORIGINAL Disto, still works fine (re-celled a couple of times), has a nice rubber protective casing (easy to wash when it gets covered in s**t from being poked down manholes). Yes on flowing water you just get the surface, but how often do you need an exact level - generally you can estimate how far up the main pipe the flow is and correct the reading. Good when the manhole is very deep and the rod would need to be a telegraph pole.
If you do need an exact level, especially side entries where I have seen pipes occasionally reversed, so the "invert" you see is actually the collar, then the guaranteed way is rods and a probe. We use the standard 1 metre target pole extension rods (which are striped in 5cm. segments). We have a series of flat stainless steel bars with a 5/8" bolt on the top at one end. Bars are 0.5, 1 and 1.5 metre long, so you can hold the rod vertical and measure to just about any invert inside a manhole you don't want to enter. The probe means you get well inside the pipe.
I only use disto in dry holes or those with little flow such as the periodic flush blast manhole.
Average flow=25' tape. High flow=level rod.
I have a couple of TackLife distos, one is strictly slope and has two level bubbles and a site line, the other converts to all types of readouts for slope, horizontal, vertical and area and a couple others.
and a site line,
Spelling police: you need a SIGHT line when you work at the SITE.
Any other options that correct for slope??ÿ Perhaps in the ~60' range??ÿ Even better if they have the ability to do min/max measurements.?ÿ Basically, I'm looking for the cheapest one so that when I drop it down the MH, I cry the least.?ÿ Thanks.
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EDIT:
As you said, the literature is silent on correcting for slope.?ÿ I presume you found it buried in the features/options menu??ÿ By chance, can one also do a min/max measurement with it??ÿ Thanks again.
Some distance meters / laser rangefinders, like my Leica Disto X4, have a mode for continuous readings with recording of minimum and maximum values. Handy for finding the perpendicular distance to a wall (minimum) or the distance to an interior corner of a room (maximum).
Yes, exactly. If one scrolls down past the pictures in the following link to the "functions" literature, you can see how Leica defines their "Min/Max Measure" mode:
https://www.sccssurvey.co.uk/leica-disto-guide