This may sound picky but when it comes to dead flat grades (0.5% or flatter) I prefer somebody to get down in the manhole with the grade rod & a 4?? carpenters level for the inverts coming in so long as the flow & fumes allow. Men up top hold the rod level & shoot with the automatic level. The invert out can typically always be rodded with just a vertical rod as the manholes around here are eccentric with the lids & steps over the inverts out.
I say the easiest and best way to get invert elevations is the two-prisms-on-the-rod method.
You can hold the rod at any angle and get horizontal and vertical location at the same time.
I wasn't lambasting you. I agree completely and have been OSHA trained beyond where most people even want to know.
I was just agreeing with the dont send anyone down into a manhole unless absolutely necessary. And with land surveying I can't see why you ever would descend into one.?ÿ
I say the easiest and best way to get invert elevations is the two-prisms-on-the-rod method.
You can hold the rod at any angle and get horizontal and vertical location at the same time.
Do you have a spreadsheet that helps with that XYZ math?
Plus, I would still think in reality we are talking +-0.1-0.2??.
I am picturing an old nasty sanitary sewer with rough conditions at the inverts as well as a 25?? fiberglass extension rod sort of curving as it leans while taking prism shots at two different section heights. ?ÿThis is all in my head, though, I admit I have never actually tried this.
I usually do measure downs very first thing on the job, before control is set even. ?ÿOne, it gets the nasty out of the way early. And B, it often identifies that one more structure downstream or upstream that I might have missed otherwise.
Why does everyone assume
Because this is a land surveyor??s message board. ?ÿIt is what we do.
I was taught to always measure from the most northerly point on the rim and have been doing so for decades. When I was a neophyte I reported depths to the nearest 0.01'. After I got some experience i changed to 0.05'. Now that I am old I only report them to the nearest 0.1' regardless of what accuracy the crew reports.
My thoughts are that ?ñ0.1' can't really matter in the real world...
I prefer somebody to get down in the manhole with the grade rod & a 4?? carpenters level for the inverts coming in so long as the flow & fumes allow. Men up top hold the rod level & shoot with the automatic level.
I've been solo for so long now that I wouldn't know what to do with a 3-man crew.
We always had 2 rods.
The level loop rod and the ???? stick.
Unless you were new. You only had a ???? stick then. And never ate lunch after dipping manholes.
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Yeah, I have dedicated rod for dips.?ÿ I always wear surgical gloves, wash the rod down with simple green or some other cleaner and then wipe the rod down with bleach wipes.?ÿ I'm know the thing is still not even close to clean.
There was a big project around here many years ago to locate 120,000 manholes to 0.01 feet H and 0.01 feet V. And this is not a flat area.?ÿ
Unreasonable spec from an engineer. He didn't understand that just because coordinates and elevations are listed to 0.01 feet that they aren't accurate to that level.?ÿ?ÿ
We formed a team, went after it (got the spec lowered to 0.1 feet H and V). If I recall correctly there were 5 firms/teams that went after it. Four of us were all around the same $/mh. Of course the out of town firm that bid much lower got it, and then protested because they didn't realize you couldn't get them all with RTK. They gave up. Anyone who has ever been to western PA will understand that RTK is not possible on many of the manholes because they often don't run in the streets but rather in the stream valleys which are usually wooded.?ÿ
Maybe nowadays with more constellations it would be possible to RTK a higher percentage, but this was back around 2005 or so.?ÿ
that sounds typical of an out of town firm missing the mark. they should've done some more preliminary investigation first & I can't believe they didn't think about sanitary sewer outfalls following the natural drainage off the land...?
Unreasonable spec from an engineer.
Say it ain't so....
In Trimble access there is a two prism function. You give it the measurement from the bottom of the pole to the first prism, then the distance to the second prism. You shoot both (holding it steady it the tough part). Then it stores all of the readings and computes and stores the coordinates/elevation of the tip of the rod. Great tool. Here we were doing topo of a tunnel...
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If the spec is 0.10'x0.10...no you cannot get that with RTK...not even now. The laws of physics haven't changed.
I disagree, I can consistently get 3 cm (0.1 feet) using a local base RTK. We do a lot of leveling, and GPS, and I have a lot of data that could prove that. Of course there are outliers. But 95% of the time...
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But back then we weren't going to do RTK, the winning bidder tried it and failed. Things are different now with more SV's.?ÿ
a local base.?ÿ
Probably the key.
Maybe 4 man crew.?ÿ If you have one in the hole you have to have one monitoring his actions.
And a hoist to get him out if anything goes wrong...oh and that is parked (attached to the guy???) in the middle of the road. I never wanted it attached. I figured I was more likely to get pulled out of the hole after a car hit the hoist then I was to pass out.