Please advise the best 8' metal prism pole with most accurate leveling bubble.
Most poles come wit a 20 or 40 minute bubble, an 8 minute bubble replacement can be purchased. I use a pole with the 8 minute bubble for precise work. Site pro makes a pole that is graduated on the exterior of the pole. I really like it.
victorstone, post: 374887, member: 618 wrote: Please advise the best 8' metal prism pole with most accurate leveling bubble.
From my limited experience, there is no best metal prism pole. Poles get dropped. hit upon, kicked rolled and cause the pole to bent.
Prism bubbles can be easily purchased and replaced in the holder.
Best method is to properly take care of the equipment and not like what's mentioned above and also to always check the plumb of your bubble before precise work. Bubble jig adjuster can be purchased from seco to check and adjust your bubble
Thats my 2 cents worth.
Just recently checked the results of a "precision" job (monitoring canal wall movement) a friend did. Came up with different results. Turns out his expensive prism pole was off by 0.04'. Why he never calibrated his pole in years I'll never know. I built a pole jig out of spare parts for free. But if you're not cheap like me, you can buy one for less than $50.
Any precise work, my recommendation is calibrate before you leave the office. Only takes 5 minutes.
Bent: agree. It is hard to find a pole out of the factory box that does not have some 'run out'.
[INDENT=1]I define 'run out' as the total distance traveled by the top of the extended pole if it is constrained on the bottom and the middle, then rotated 360'. Look at the top, perhaps use a dial indicator to measure the back and forth centering error as the pole is rotated.[/INDENT]
I am impressed if I find a pole that has less than 3 mm of run out. It makes me crazy. I have screwed around with my personal poles trying to get them straight and it is futile.
I certainly can adjust the bubble, and I have a few poles with 8-minute bubbles. But run out makes me crazy.
...looking for answers...
M
My dad went CRAZY over this exact question last year. He spent months with a transit check hundreds of different setups. There are 3 things you need to look for
- Obviously bubble precision- most manufactures allow you to upgrade the precision. 8 minute is the best off the shelf bubble i know of.
- How straight the pole is from top to bottom. It's very surprising how inconsistent some of the top prism pole manufactures can be.
- How centered is the threads/quick connector to the center of the prism. Another shocker
The best pole that we have ever seen from any manufacture consistently has been the Leica GLS12/GLS11. I don't know who is manufacturing the pole for Leica. I suspect that its NEDO. NEDO makes the best tripods in my opinion, but that's a different subject. We believe you should be able to achieve 3mm with this pole AND a good prism.
Best thing to do is go to a dealer that has a few poles and bust out the transit with locking tangents.
2m with and 8 minute bubble - List $250.00
I can see if i can get some photos of how we test this to prove how nice it is.
Eric Kara, post: 375029, member: 1598 wrote:
The best pole that we have ever seen from any manufacture consistently has been the Leica GLS12/GLS11. I don't know who is manufacturing the pole for Leica. I suspect that its NEDO. NEDO makes the best tripods in my opinion, but that's a different subject. We believe you should be able to achieve 3mm with this pole AND a good prism.Best thing to do is go to a dealer that has a few poles and bust out the transit with locking tangents.
2m with and 8 minute bubble - List $250.00
I can see if i can get some photos of how we test this to prove how nice it is.
Hello Eric,
is that 3mm extended to 2.05m, or down at 1.45m? this pole can be adjusted to far better than 3mm at the height you want the best results. Failing that the spigot mount allows you to take readings in two bubble positions virtually eliminating any bubble inaccuracy. A good pole I agree.
Hixon poles are very good.
I have several, over 20 yrs old.
I'd be curious as to how they test with Eric Kara.
Adam, post: 374894, member: 8900 wrote: Most poles come wit a 20 or 40 minute bubble, an 8 minute bubble replacement can be purchased. I use a pole with the 8 minute bubble for precise work. Site pro makes a pole that is graduated on the exterior of the pole. I really like it.
I never use the crap bubbles on prism poles. I recommend using those plastic post leveling gizmos you can pick up for five bucks. Although they look to be cheaply made, the level bubbles are accurate, highly visible, easier to plumb, and more importantly easy to check daily and "repair" (read: replace) if they test to be out of adjustment.
The problem with standard prism pole level bubbles is that, although they can be adjusted, the adjustment is highly unstable. What you do is render the pole truly plumb using a plumb bob based jig, where you have a permanent or semi permanent hole in (lets say) a door threshold, and a hanger point for a plumb bob directly above it. Before using the jig to adjust a pole, you check that the plumb bob hanger point is exactly over the hole by using (you guessed it) a plumb bob. You can then put the point of the prism pole into the hole (hopefully sized properly for this use), and move the top of the pole to be perfectly plumb, by placing it directly under the plumb bob tip, after having suitably shortened the plumb bob string so that this works. You would then clamp the upper part of the pole so that it remains immovable and plumb, and check/adjust the errant level bubble of the prism pole. We always did it this way, until one day we noticed that after adjusting the bubble back to level, it would slowly drift off over a period of about 10 minutes. Turns out this was because of stresses in the rubber "spring" that the adjustment screws work "against". Once we became aware of this, we found that it took forever (meaning several adjustments, each with a waiting period) to get a stable adjustment of the bubble, such that the pole was considered safe to return to service. Other folks may use other jigs or methods, but the problem is that the adjustments you make to the pole bubble are not stable, and most surveyors don't know this (we certainly stumbled onto the fact by accident).
My solution to the above problem was to abandon the use of the manufacturers bubbles, and use the cheap post leveling gizmos carpenters use to level up 4X4 posts when building porches and decks. The thing about these PLGs (Post Leveling Gizmos) is:
1. The PLG bubbles are accurate although they may or may not be perfectly perpendicular to the corresponding bearing surface of the device. The non perpendicular surface problem is NOT a problem because you can detect that issue (and avoid or toss the rare defective PLG) so easily. By the way, you can easily buy a PLG at any home improvement center, and prove to yourself that its bubbles are MORE sensitive than the bubble that came on your pole. The PLG bubbles are much longer and more sensitive, and will register small shifts that the original equipment bubble will not "notice" (meaning that you or I will barely detect that the original pole bubble is out of center by eyeball).
2. The detection of the rare PLG in which the either of the two bubbles is not perpendicular to the corresponding bearing surface is very easy. You just level the pole using the PLG and fix the pole so it cannot move out of level. You then rotate the PLG 180 degrees to the other side of the pole. It says not level? Then toss that PLG and buy another one for five bucks. That PLG has an accurate bubble, but the bubble is not at right angles with the corresponding bearing surface that touches the pole (or 4X4 if you are a carpenter).
3. Each PLG has TWO accurate bubbles, which are so easy to check (by turning the pole 180 degrees while preventing any motion other than spin) that any problem in the PLG bubbles alignment with the bearing surfaces of the PLG can be detected quickly and easily in the field. If you find that you have knocked a bubble out of alignment, you can mark it or tape it over, and use the other bubble to level left-right only when you are doing an angle, and front-back only when you are shooting a distance. This will work in a pinch until you can get back to the truck and get an undamaged PLG.
4. These PLGs are CHEAP (5 bucks). So, whereas adjusting an original equipment bubble on your pole takes expensive field crew time (and does not work terribly well), "adjusting" an out of adjustment PLG involves chucking it and going to the truck for another one (of which you should have several spares, as they are dirt cheap). Check the new one before you use it (because it is easy, the crew guys WILL do that). I generally buy several, and check them in the store before I purchase them. To do this, find any upright pole or shelf bracket that you can "check for level" using a PLG. When you find one that reads level, and also reads level if you put the PLG on the opposite side of the support or bracket, you have found a perfectly plumb pole or bracket in that store. Use it to check however many PLGs you want to buy. I always pick up five or six at a time.
5. A minor point, but the PLGs I buy are usually bright orange, bright green, or yellow, and are highly visible. This is never unhelpful when surveying in the field.
Once you start using PLGs on your poles, they are so cheap, handy, accurate, easily checked and easy to read that you will never bother with the original bubbles, once they go out of alignment. I don't know (having not done the math) but I suspect that the bubbles on the typical PLG are in the range of five minutes or better. Should be easy to check. I no longer have a "prism pole bubble adjustment jig" because the PLGs work so well and are so easy to field check. Anyone who has a jig like this could easily determine the bubble accuracy of a PLG.
Anybody up for that experiment?
Hello John,
John Wetzel, post: 375074, member: 11747 wrote: The problem with standard prism pole level bubbles is that, although they can be adjusted, the adjustment is highly unstable.
I would disagree with this blanket statement. i can't speak to the reliability of other manufacturers bubble mounting systems, but we use the leica GLS11, GLS12 and GLS14 and i find the bubble stays where it is adjusted to within a mm or two. I'm not even sure they wandered that much, they probably weren't adjusted any better than this in the first place. Though I can now do better.
So, whereas adjusting an original equipment bubble on your pole takes expensive field crew time (and does not work terribly well)...
well i find i can adjust the bubble on a pole now to under a mm in a few minutes (by myself if i have to) with a single robotic total station. and i didn't really have to do the last adjustments that i did; i just wasn't satisfied with 1.5mm out of level and had to get to <0.5mm.
yes, i do have an accuracy/precision fetish that goes beyond what is sufficient for cadastral work.
Eric Kara, post: 375029, member: 1598 wrote: My dad went CRAZY over this exact question last year. He spent months with a transit check hundreds of different setups. There are 3 things you need to look for
- Obviously bubble precision- most manufactures allow you to upgrade the precision. 8 minute is the best off the shelf bubble i know of.
- How straight the pole is from top to bottom. It's very surprising how inconsistent some of the top prism pole manufactures can be.
- How centered is the threads/quick connector to the center of the prism. Another shocker
The best pole that we have ever seen from any manufacture consistently has been the Leica GLS12/GLS11. I don't know who is manufacturing the pole for Leica. I suspect that its NEDO. NEDO makes the best tripods in my opinion, but that's a different subject. We believe you should be able to achieve 3mm with this pole AND a good prism.
Best thing to do is go to a dealer that has a few poles and bust out the transit with locking tangents.
2m with and 8 minute bubble - List $250.00
I can see if i can get some photos of how we test this to prove how nice it is.
I am glad somebody had success with this pole. We have only had one of these and it didn't last too long. Maybe we got a lemon, and from your opinion I will assume we did. After about 8 months of using it the grip started to slip up and down and if you weren't careful the antenna height would fluctuate or the top of the pole would just come right off. Like I said, maybe we got a lemon. I would like to see your tests also.
Mark O, post: 374932, member: 11591 wrote: Just recently checked the results of a "precision" job (monitoring canal wall movement) a friend did. Came up with different results. Turns out his expensive prism pole was off by 0.04'. Why he never calibrated his pole in years I'll never know. I built a pole jig out of spare parts for free. But if you're not cheap like me, you can buy one for less than $50.
Any precise work, my recommendation is calibrate before you leave the office. Only takes 5 minutes.
No purchase is necessary for a telescoping prism pole. I drilled a hole in the top of the door jamb at the office then plumbed down and drilled one in the floor.
I can put a spare tip on top of the pole and extend it up until the tips are in the holes in a plumb line. Then rotate the prism pole to ensure the bubble is level in all directions. I do this every couple of months or so with all my poles.
I use Seco poles with an adapter for the Leica prism connection. I can remove the adapter and put the regular threaded end on for just this purpose. I've gotten excellent results after calibrating these poles.
For the 2M fixed height pole, I setup any instrument with a vertical crosshair and site it from multiple sides when it's supposedly level. The adjusting process is a bit more of a pain this way though.
Mark Silver, post: 374961, member: 1087 wrote: Bent: agree. It is hard to find a pole out of the factory box that does not have some 'run out'.
[INDENT]I define 'run out' as the total distance traveled by the top of the extended pole if it is constrained on the bottom and the middle, then rotated 360'. Look at the top, perhaps use a dial indicator to measure the back and forth centering error as the pole is rotated.[/INDENT]
I am impressed if I find a pole that has less than 3 mm of run out. It makes me crazy. I have screwed around with my personal poles trying to get them straight and it is futile.
I certainly can adjust the bubble, and I have a few poles with 8-minute bubbles. But run out makes me crazy.
...looking for answers...
M
Mark, if you calibrate your poles at half extension you will halve the total effect of run-out over the entire length of the extension. So your 3mm runout becomes -1.5mm down low, perfect at middle and +1.5mm at full extension. if you can make do with that.
