How many of you guys are using them? Big fan over here because of their transportability and minimization of certain errors when using a total station.
When I started in this business c.1990 we would cut a staub (relatively straight branch) with a machete and position it over the backsight point (usually a slightly stouter short staub with a nail) using a plumb bob. We thought we were really styling if we used an actual sawn hub and lath for the purpose. My, how expectations have changed.
@norman-oklahoma Traversing in the woods back in the day we rarely used a tripod and prism for a backsight because it meant you'd have to go back and get it to move it forward when you were traversing in the opposite direction. So many ways for a 2 man crew to set a backsight. In one interview I was asked how many ways I knew to set a backsight and I asked them how much time did they have. After five or so the interviewers all in unison announced 'good enough'. Funny enough, none of the methods I'd learned were taught in school but learned from working with old timers.
Just because I'm paranoid, doesn't mean they aren't out to get me.
Rothbucher doesn't exactly give those little tripods away -- Berntsen lists them at $385, and that's before you've added a 5/8-11 adapter.
They do looks pretty useful, though. Maybe I'll try my hand at a homebrew version...
The main downside to the mini tripods is you are shooting close to the ground so over a hot surface the instrument is looking a very fuzzy prism (from experience shooting mini prisms) and I find the distance will measure consistent but bearings jump around which makes sense to me.
After five or so the interviewers all in unison announced 'good enough'.
I'm listening...
@lukenz That's a great point. Have you noticed a big difference between a 5' HT vs 1'? That would be a fun test to run.
Rothbucher doesn't exactly give those little tripods away -- Berntsen lists them at $385, and that's before you've added a 5/8-11 adapter.
They do looks pretty useful, though. Maybe I'll try my hand at a homebrew version...
If you don't use them for scanning and just TS work, the Jeoc's are a cheap alternative. Just buy a few extras, they're like $35 each plus some fairly expensive shipping.
Being able to pop the scan target on/off magnetically & the fact they fold right up makes the RS worth it for me as I do a lot of scanning.
@jim-frame $33 with 2 spirit vial levels.
Seems like the type of product I'd be willing to buy from them (with some testing to confirm it's centering tight, also to get proper HT- maybe with a vernier?):
@jim-frame $33 with 2 spirit vial levels.
Seems like the type of product I'd be willing to buy from them (with some testing to confirm it's centering tight, also to get proper HT- maybe with a vernier?):
I was thinking a height gauge would work well for measuring HT
I'm listening...
Besides today's common ways of setting up a tripod or rod/bipod there are various manners of plumbing a staub or a lath over the point with a plumb bob. One variation involves sharpening the top of the lath or staub to a point and, perhaps, carefully wrapping it with flagging (if you don't have paint available). I used to have a target printed on the back of my business card, which I would then slip into a little split on the top of a lath made with the machete or a pocket knife. Another option involves a small nail with a little "sail" of flagging, which can go right on the hub or nail at ground level or on top of a lath. I think that it was Bruce Small that wrote of having a brick with a pencil line on it that he puts down for a backsight. The combinations and permutations are nearly endless.
Very accurate as the line is right over the point, and if it gets run over or stolen, there is fifty cents gone.
A variation on that theme that I have used is a wood hub, similarly marked and weighed down by the cone.
Very accurate as the line is right over the point, and if it gets run over or stolen, there is fifty cents gone.
Is this back in the day of pulling steel or do you use DR on it?
I think this would be just to zero the gun during the setup.
T. Nelson - SAM
Several decades ago, back when a lot of important stuff was chained in because the newfangled EDMs were not 100% trustworthy, we always did a backsight with a plumb bob. The string is very skinny and with a little practice, one could get very steady. My trusty plumb bob has been on my side for many a traverse mile but sadly hasn't been used in a long time.
I find even at pole height shooting 100-150m+ down a road from one side to the other to a GMP101 the distances will be 1mm variation but the angle (ATR) can jump around up to 10mm; I'll keep pushing the measure button 10 times for so and watch for average then store that. On occasion where I've setup a tripod back sight I've looked at the target and it can be impossible to get clearly focused though the heat haze.
My working theory is if you can't focus on the prism properly then neither can the ATR; I've not stumbled across any research on this though. I'm also wondering if using a full size prism would help vs the GMP101 as more for ATR to reference??
Shooting prisms close to the ground increases the heat haze. Had a monitoring job for a house a few years ago where we couldn't see from the TS down to a mini prism on all control points so were using a Leica GMP111 with one section under it. Problem was the prism was only just visible over ground level on some shots and I remember them jumping around more than I wanted. We didn't want to use another pole section as would have blown out our 2d plumbing. In hindsight we should have just used the extra rod section, used a couple of short sticks like a poor man's bipod and shot the pole reversing it 180° between shots to mean out any pole bias (not bubble error, any slight imperfection in pole).
Another thing I thought about when watching your video was nearly all poles have some imperfection (1-3+mm of runout/banana/bow) which is ok if you only use at one height as you can adjust your bubble so both ends are plumb but if adjustable then it changes. You addressed the pole bubble error but using the mini tripod avoids the pole runout systematic error also which is another plus.
For boundary work most of my control points are 0.2-0.5m deep so I'd need a mini tripod where you had a short pole down the centre that could slide down.
... For boundary work most of my control points are 0.2-0.5m deep so I'd need a mini tripod where you had a short pole down the centre that could slide down.
Those are available if I'm reading you right.
No I'm familiar with prism sliding on the pole option. What I want is one of those mini tripods where the pole slides up/down so I could have the mini tripod around the hole and slide the tip of pole down to the mark in the hole.
More like the below but you could put a 0.45m mini pole in it instead:
If anyone was into 3d printing then something like https://www.ths-concepts.co.uk/thsp75-survey-prism-holder/ would be an option for a low cost system (probably not strong enough to put a mini pole down for me through)
If anyone was into 3d printing then something like https://www.ths-concepts.co.uk/thsp75-survey-prism-holder/ would be an option for a low cost system (probably not strong enough to put a mini pole down for me through)
Very cool!