Last Sunday, I had the pleasure of conducting an underground survey. It had been a few years since I was underground so I wasn't sure if things would close in on me. Thankfully, that wasn't a problem.
Photo of my Wild ZBL plummet set under a bolt in a steel I-beam at the portal.
Thankfully, I didn't have to hike very far with the equipment. 🙂
A look across the valley. Overall, a great day to survey at timberline even if it was underground. Panoramas, plus some fascinating geologic structures underground.
That's pretty awesome. I know how it feels to do a survey in a unique area for the first time. Also, is the theodolite in the first pic the same as in your second?
The second photo (recropped) is looking out from the portal. The instrument in the photos is a Wild ZBL zenith/nadir optical plummet. It is much lighter than carrying a ladder to hang a plumb bob from the spads. My theodolite (a T-2) is still in the back of the truck.
And yes, the photos show that it has been a while since I set under a point. Quite the college-boy setup with the tilted tripod head and tribrach hanging ten!
Never thought until now but I can just rock up with my legs and instrument, plonk it over the mark and in a few swift adjustments be setup vertically OVER a point.
Not sure how I'd go doing same UNDER a point.
Probably flounder about for a while.
For the purists, no I don't just slam the legs down and stamp them in with my big hooves with the jigger (TS, Gun) mounted on top and jar the guts out of it. I love my Nikon too much for that :totalstation:
Setting up under a point is the same principal as setting up over a point, except that you are looking up and not down.
Agree but it's that inherent knack that comes with years of setups that one can vertically orient oneself over something, but not necessarily under something.
The eyes don't function same rolling them down as they do up.
I reckon it'd be an interesting excercise. Lineup a dozen surveyors and see how we fair over and under.
I reckon those who've never done it consistently under could soon be seen.
I typically attach the string on my plumb bob to the bottom of the tripod mount and let it hang so the plumb bob (point down) is on the center of the nail. I do this to get the most accurate measurement so it would be quite hard to do this in this case.
Richard, post: 450956, member: 833 wrote: Never thought until now but I can just rock up with my legs and instrument, plonk it over the mark and in a few swift adjustments be setup vertically OVER a point.
Not sure how I'd go doing same UNDER a point.
Probably flounder about for a while.
For the purists, no I don't just slam the legs down and stamp them in with my big hooves with the jigger (TS, Gun) mounted on top and jar the guts out of it. I love my Nikon too much for that :totalstation:
My favorite tool out of all of mine has to be my Leica Viva TS11. That's why I use the plumb bob.
Setting up under the point has to be harder. The trick of aiming the plummet at the point below and then leveling by changing the lengths of legs to get close to the right position would work AGAINST you when looking up.
I used to have a Pentax GT6B Transit as well but I sold that because the swivel mechanism stopped working.
Bill93, post: 450971, member: 87 wrote: Setting up under the point has to be harder. The trick of aiming the plummet at the point below and then leveling by changing the lengths of legs to get close to the right position would work AGAINST you when looking up.
That's another thing. My new picture shows my Leica on a tripod that is set up over a point in a curb. I was doubtful that the legs of the tripod would cooperate with one leg being lower than the other two, but it worked out quite well and it lined up perfectly with my prism.
Gene Kooper, post: 450952, member: 9850 wrote: My theodolite (a T-2) is still in the back of the truck.
Where are the olive green boxes and cans? Everything looks so...so ORANGE!
DDSM
Dan B. Robison, post: 450978, member: 34 wrote: Where are the olive green boxes and cans? Everything looks so...so ORANGE!
DDSM
Well, I still use a new-style T-2 (with a Rite-in-the-Rain data collector!).
Gene Kooper, post: 450983, member: 9850 wrote: Well, I still use a new-style T-2 (with a Rite-in-the-Rain data collector!).
Is that tripod a new one? It looks pretty nice and new.
Gene Kooper, post: 450983, member: 9850 wrote: with a Rite-in-the-Rain data collector
:gammon:
Gene Kooper, post: 450983, member: 9850 wrote: Well, I still use a new-style T-2 (with a Rite-in-the-Rain data collector!).
Gene,
I think I may have soon extra Batteries for your Data Collector (0.5mm H, 2H, & 4H).
I switched to Ink about 35 years ago, but the old Lead (graphite) should still be good (NOS_New Old Stock).
🙂
Loyal
Setting up under a plumb bob isn't that bad. There is a dimple in the top handle of a Leica 1200 Robot. After the plumb bob stops swinging, I balance the tripod on one leg getting the instrument level and under the point, then set the two remaining legs down and step them in. The next step is to use the legs to get the instrument back under the point, then level with the tribrock screws then adjust back under the point with the legs, then level again and slide on the plate to center and final level. It takes a little getting used to, but not too bad.
ARS Mine Surveyor, post: 451094, member: 12913 wrote: Setting up under a plumb bob isn't that bad. There is a dimple in the top handle of a Leica 1200 Robot. After the plumb bob stops swinging, I balance the tripod on one leg getting the instrument level and under the point, then set the two remaining legs down and step them in. The next step is to use the legs to get the instrument back under the point, then level with the tribrock screws then adjust back under the point with the legs, then level again and slide on the plate to center and final level.It takes a little getting used to, but not too bad.
When I first surveyed underground I used a plumb bob, but found carrying a ZBL plummet or SNL laser plummet is much lighter than dragging a ladder around underground.
The hard rock mines I've worked in all had high backs to accommodate the vent bag so flipping the plumb bob string into the spad hook usually doesn't work very well. I use the forced centering method with three tripods and Wild illuminated targets. They work great, esp. for short backsights. The miners are following a vein that is definitely not straight, One backsight is 117 ft. the other 72 ft. Working in a lower level several years ago, I had backsights as short as 23 ft.
Over the years I've had other surveyors interested in working underground. Every one of them struggled initially because everything is arse backwards.
Gene Kooper, post: 451098, member: 9850 wrote: When I first surveyed underground I used a plumb bob, but found carrying a ZBL plummet or SNL laser plummet is much lighter than dragging a ladder around underground.
The hard rock mines I've worked in all had high backs to accommodate the vent bag so flipping the plumb bob string into the spad hook usually doesn't work very well. I use the forced centering method with three tripods and Wild illuminated targets. They work great, esp. for short backsights. The miners are following a vein that is definitely not straight, One backsight is 117 ft. the other 72 ft. Working in a lower level several years ago, I had backsights as short as 23 ft.
Over the years I've had other surveyors interested in working underground. Every one of them struggled initially because everything is arse backwards.
I guess I lucked out. The salt mine is room and pillar and my backsights are typically longer than my foresights. My truck in the picture avoids the ladder issue. The roof varries from 12 to 18 feet and we don't have hook type spads. The laser plummet would be handy, but I only use one tripod and hang a 360 prism from the backsight spad then move to the foresight and set the new centerline point.
ARS Mine Surveyor, post: 451158, member: 12913 wrote: I guess I lucked out. The salt mine is room and pillar and my backsights are typically longer than my foresights. My truck in the picture avoids the ladder issue. The roof varries from 12 to 18 feet and we don't have hook type spads. The laser plummet would be handy, but I only use one tripod and hang a 360 prism from the backsight spad then move to the foresight and set the new centerline point.
Pretty nifty truck!
I just have a standard 1998 GMC Sierra with racks (see pic below).
But I do like your technique of using the equipment in that sense get an accurate foresight and backsight in an underground survey.
