We made a spreadsheet for this that we laminated and taped onto the back of the clipboard. You basically have to either guesstimate the angle of your rod or use some kind of angle measuring to device.
But yeah, like the guy above said, it's basically just using cosine. The spreadsheet was easier than having to whip out the calculator in the middle of traffuck and was plenty accurate enough for most applications.
Dm me, and I'll see if I can find a copy of it on Monday when I'm back in the office that I can send you.
That's what I do, I do it regularly because I work mainly in ROW and design survey work for municipalities. The angle function on your iPhone works great...don't drop it.
They make something that makes this a little easier. And faster. I’m not sure if it’s hugely accurate, but I’m sure it’s good enough for 99% of work. Looking at you NASA.
https://preview.redd.it/mhmjx5ex791d1.jpeg?width=1179&format=pjpg&auto=webp&s=3ec694102c7e62749e330ea535b31c7e64f6ec59
Right on man. I figured it was pretty close. Honestly, they could make it a little bit smaller, even if it sacrificed a little accuracy. I’d much rather be able to put it in my pocket. Normally, I’m throwing on my ten pocket toolbelt just to carry this. It helps because I generally have a couple other things on me. But a .25’ version be awesome to have as well. Like if I’m just pulling an invert or two instead of doing a drainage study. But it still beats the pain in the ass of a pipe mic. And if two hundredths or so is not satisfying your engineering requirements, then the engineers should be doing something much more fulfilling than stormwater and sanitary work.
Fully agree. Sewer structures aren't swiss watches. But yeah, they're always half an inch too big for the big pockets on the safety vests.
I'm actually making a full fledged program for my master's right now, to help automate the full process of analyzing field notes for dips and making pipe networks. The simple fact of using the angle measurer is what jump started the whole process. I'll try and post that soon, within the next couple of months.
Algorithm is based on stable marriage problem.
https://youtu.be/Qcv1IqHWAzg?si=8hmZtTAXX_C2s6S0
Assign weights to certain observed pipes in each structure based on likelihood of it matching up with another observed pipe in a different structure. From there, perform stable matching, and end product is (hopefully) an accurate pipe network.
Nice idea. How stringent are the field notes requirements? I'd expect making that data more structured would be a necessity?
I've adopted a hybrid GIS style approach so that the entire network can be constructed in the field. All data captured on the instrument with pipe attributes assigned to the linework, rather than points. Rather than describing points for each invert, I use a short line going from the invert (HZ position) in the direction of the pipe (with depths added via attributes). Then extend/join the line when I survey the next MH.
Yep we did it a lot at a place where we had massive manholes that were offset from the access hatch. These were big trunk lines and normally the flow line was not directly down from the manhole opening.
So we would dip it diagonally with a threaded steel pipe, and mark where the diagonal hid the rim.
And put an 18" torpedo level on the pipe, vertical, then measure the offset from the top of the vertical level to the diagonal pipe.
Then from there boom, we had our triangle. So you could either solve for the angle and use trig, or just do ratios. You're basically doing the same thing at that point.
It worked pretty well, and we didn't really have a choice since these manholes were so far off from the centerline of the pipe. I thought it was actually an ingenious idea.
That's a masterful gambit good sir. In my case, the site developer was complaining our measurements were not accurate due to the lean. Someone posted here the other day about using Pythagorean theorem to find the invert also, which I found interesting as well.
Yep same thing. That works too. It's just similar triangles.
You could do it with a 6-inch level as well, but the problem is they're not quite accurate enough for a big 20 or 30 ft dips. At least that's what we found. The 18 in is a good compromise. A three or four footer would probably be better but definitely a tougher job.
The trig equations you need are printed on the inside cover of most fields books. Cosine of the angle times the hypotenuse is what you need. Also Google the Leica Disto. It is a laser range finder and some models have built in vertical angle measurement and automatically do the trig function. I used this method for ages and is great as long as the structure is not filled with liquid.
I’m pretty sure what he was doing is multiplying the rod reading by the cosine of the angle.
Interesting. I'll experiment with that method. Thanks.
We made a spreadsheet for this that we laminated and taped onto the back of the clipboard. You basically have to either guesstimate the angle of your rod or use some kind of angle measuring to device. But yeah, like the guy above said, it's basically just using cosine. The spreadsheet was easier than having to whip out the calculator in the middle of traffuck and was plenty accurate enough for most applications. Dm me, and I'll see if I can find a copy of it on Monday when I'm back in the office that I can send you.
That's what I do, I do it regularly because I work mainly in ROW and design survey work for municipalities. The angle function on your iPhone works great...don't drop it.
They make something that makes this a little easier. And faster. I’m not sure if it’s hugely accurate, but I’m sure it’s good enough for 99% of work. Looking at you NASA. https://preview.redd.it/mhmjx5ex791d1.jpeg?width=1179&format=pjpg&auto=webp&s=3ec694102c7e62749e330ea535b31c7e64f6ec59
This is exactly what I use for dips. Stock up at Ace Hardware when I go. The math comes out to within a couple hundredths of just a straight level.
Right on man. I figured it was pretty close. Honestly, they could make it a little bit smaller, even if it sacrificed a little accuracy. I’d much rather be able to put it in my pocket. Normally, I’m throwing on my ten pocket toolbelt just to carry this. It helps because I generally have a couple other things on me. But a .25’ version be awesome to have as well. Like if I’m just pulling an invert or two instead of doing a drainage study. But it still beats the pain in the ass of a pipe mic. And if two hundredths or so is not satisfying your engineering requirements, then the engineers should be doing something much more fulfilling than stormwater and sanitary work.
Fully agree. Sewer structures aren't swiss watches. But yeah, they're always half an inch too big for the big pockets on the safety vests. I'm actually making a full fledged program for my master's right now, to help automate the full process of analyzing field notes for dips and making pipe networks. The simple fact of using the angle measurer is what jump started the whole process. I'll try and post that soon, within the next couple of months.
Interesting. What’s your method?
Algorithm is based on stable marriage problem. https://youtu.be/Qcv1IqHWAzg?si=8hmZtTAXX_C2s6S0 Assign weights to certain observed pipes in each structure based on likelihood of it matching up with another observed pipe in a different structure. From there, perform stable matching, and end product is (hopefully) an accurate pipe network.
Nice idea. How stringent are the field notes requirements? I'd expect making that data more structured would be a necessity? I've adopted a hybrid GIS style approach so that the entire network can be constructed in the field. All data captured on the instrument with pipe attributes assigned to the linework, rather than points. Rather than describing points for each invert, I use a short line going from the invert (HZ position) in the direction of the pipe (with depths added via attributes). Then extend/join the line when I survey the next MH.
Yep we did it a lot at a place where we had massive manholes that were offset from the access hatch. These were big trunk lines and normally the flow line was not directly down from the manhole opening. So we would dip it diagonally with a threaded steel pipe, and mark where the diagonal hid the rim. And put an 18" torpedo level on the pipe, vertical, then measure the offset from the top of the vertical level to the diagonal pipe. Then from there boom, we had our triangle. So you could either solve for the angle and use trig, or just do ratios. You're basically doing the same thing at that point. It worked pretty well, and we didn't really have a choice since these manholes were so far off from the centerline of the pipe. I thought it was actually an ingenious idea.
That's a masterful gambit good sir. In my case, the site developer was complaining our measurements were not accurate due to the lean. Someone posted here the other day about using Pythagorean theorem to find the invert also, which I found interesting as well.
Yep same thing. That works too. It's just similar triangles. You could do it with a 6-inch level as well, but the problem is they're not quite accurate enough for a big 20 or 30 ft dips. At least that's what we found. The 18 in is a good compromise. A three or four footer would probably be better but definitely a tougher job.
The trig equations you need are printed on the inside cover of most fields books. Cosine of the angle times the hypotenuse is what you need. Also Google the Leica Disto. It is a laser range finder and some models have built in vertical angle measurement and automatically do the trig function. I used this method for ages and is great as long as the structure is not filled with liquid.
Check [this product out](https://accurateinverts.com/) It compensates for exactly what your boss is doing and saves a lot of effort.
I've been trying to get my office to do something like this, but none of the older guys want to give it a shot.
Use a level rod with a fish eye level and lay a piece of 4ft lathe across the manhole and take the rod reading.