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Transit check

Discussion in 'Lasers' started by td25c, Apr 2, 2009.

  1. td25c

    td25c Senior Member

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    Once in awile I re-calibrate The transit.Level it up and make small adjustments.I like to be able to spin it 360 degrees without the bubble moving.Then I set it beside a pond and take readings off the waters edge in 5 or 6 places to check the settings.I guess I could send it to a tech shop,But I dont know if they could set it any better.Standing water is pretty level.This would work on a laser to.
     

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  2. danhoe

    danhoe Well-Known Member

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    Take it in !

    Your transit shown is really a level, by shooting water levels is not very accurate, wag in the pole, eye level to the gun, ect.. When you take it in to get calibrated, it is checked at a long range, 100'. Take it in, my dig. transit is a 5 second gun, which is pretty accurate, you might what to find out what yours is. I was trained by Spectra Precision to field calibrate lasers, I still take mine in. One mistake could be alot of money out of your pocket. danhoe
     
  3. td25c

    td25c Senior Member

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    I trust the water.It"s naturally level.Using this method It's checked from 5 to 200 feet going around the pond.Its taking readings at different distances at different angles.We call it a transit because the scope can move up or down to check grades.
     
  4. DarrylMueller

    DarrylMueller Senior Member

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    I think the 180 spin is all that is needed.
    I never tried the water but if you drove stakes in the water all water level it has to work, you go to the head of the class.
    I have also used the 180 on hand or pocket level, just need a level table and it works to. No real need to have someone else do what you can do. Tea Part Day 4/15/09
     
  5. td25c

    td25c Senior Member

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    I could not think of a better way to check the transit.I tape the grade stick to a shovel handel and push the shovel down until the stick just touches the water.It has to be a calm day so the water is still.That sounds like a good idea on the pocket level.
     
  6. Squizzy246B

    Squizzy246B Administrator

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    On lasers

    My laser supplies shop had an open day a couple of years back. The challenge they set up was to level a laser with a bubble to see if you could get as accurate as an auto leveller at 100'. Nobody got within a bulls roar. Most people where nearly an inch out. Bubbles are very inaccurate for setting up levels. A good laser shop will have range to fire the laser and have it well within the manufacturer's specifications within minutes. My supplier says it takes longer for him to fill out and issue the annual calibration certificate than it does to test the cal on the laser. I think it costs me $20 and I have a certified calibration. If I buying anything or getting a repair they don't charge at all.

    About 4 years ago I built a big wall alongside a shopping centre carpark. The builder rang me a few weeks later to tell me the wall was nearly 6" out of level. He was using the drainage/carpark guys dumpy site, which had never been calibrated. The builder was getting really abusive with me. I said I'd come up to the job with my calibrated laser and its calibration certificate and charge him $160/hr for a level check which he'd have to pay if the wall was in tolerance. I got a call 20 minutes later to say the wall was within 1/8" level...and the carpark and drainage was all being ripped up. $20 for certification is a pretty good insurance I think.
     
  7. td25c

    td25c Senior Member

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    Are you saying that standing water is not an accurate way to check a transit or level.If it's not a good way,then tell me a better way in detail.Do you not believe that standing water is naturally level?Our southern Indiana ponds are known for being level.
     
  8. Squizzy246B

    Squizzy246B Administrator

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    Lol, are you trying to tall me that your water in southern Indiana is more level than elsewhere on the planet?.. The egyptians didn't think so and they built some monumental structures using water as a level.

    Howver, what I am saying is the human eye may not be the most accurate means and that having your level checked by a qualified technician may be cheap insurance.

    Your method could be quite good...but it depends on you and surrounds. What I do know is that vertically sighted bubbles (centre bubbles) are horrible inaccurate especially at any distance. If you have normal bubbles (like on a spirit level) going in two directions then its easier.
     
  9. td25c

    td25c Senior Member

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    I was razzing you a bit Squizzy.I new you built lime stone retaining walls and that takes a master craftsman.Accuracy is important in any trade.I could not think of an easyer way to check the transit.I could have it calibrated at a shop ,But would still have to go out to the pond and check it to make sure they done it rite.If we want to get extremely tecknical ,the water level in center of the pond is sightly higher than the level on the ponds edge due to the earth's curvature.The Egyptions were aware of this to.They were master surveyors.They new the world was round thousands of years before anyone else did.I am somewhat bias being from southern Indiana,But I think our pond water is some of the most level water in the world.Ha,Ha!
     
  10. Turbo21835

    Turbo21835 Senior Member

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    I cant imagine not taking a gun it to have it checked. If something is wrong with your gun and you take it to a job, and have to redo something on your dime it will be a hard lump to take. Most companies that I have worked at have always taken in all their lasers and guns every winter. Its worth it.
     
  11. landrvrnut22

    landrvrnut22 Well-Known Member

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    Sorry, but I wouldn't trust that gun as far as I could throw it into the center of the pond. There is a standard in which survey equipment is calibrated to. I don't believe that shooting the waters edge in the back 40 is in the ASTM standards. If you brought that gun on my jobsite, I would laugh you all the way to the court house.

    I have my Auto Level calibrated every year. Costs me $50. I don't trust lasers all that much, as they are not near accurate enough. They are good for fast setups, and one man operations. Most are accurate +/- 1/8" in 100', where my gun is a Sokkia C20 accurate to +/- 1mm in 1km or .039" in 3280'

    Don't be a cheap skate, get it calibrated.
     
  12. Squizzy246B

    Squizzy246B Administrator

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    I think we look for 1/8th at 1000 feet for my laser.

    There, I was trying to be tactful.:rolleyes:
     
  13. Kgmz

    Kgmz Senior Member

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    Hate to tell you this, but your C20 only has a accuracy of 1/8" in 100'.

    I think you are confusing "per km double run leveling deviation" with working accuracy. The double run deviation for the C20 is 2.5mm, whereas the deviation is 1mm for the better auto levels. Not sure where you got the 1mm figure.

    Link to brochure for C series auto levels. Same brochure as available at the Sokkia US website, but theirs is not directly linkable.
    http://www.stakemill.com/pdf/brochures/sokkia/cseriesautolevels.pdf

    Most decent lasers have a accuracy of 1/16" in 100' and have a working range of 2000 to 2800 ft. Your C20 has a working range of 150 ft.


    Even my David White LT8-300LTU, LT(level & transit) & LTU(line transfer unit) which is not a auto level. Has the same accuracy as the C20 and greater range since it is 26X, working range is 400 ft.

    LT8-300LTU brochure
    http://www.lascolaser.com/pdfs/lt8300ltu.pdf
     

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    Last edited: Apr 11, 2009
  14. DeLong

    DeLong Member

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    For a level run a "two peg test" if you dont want to take it in. Google it and you'll find some good directions.
     
  15. td25c

    td25c Senior Member

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    Howdy Delong .I have herd of the two peg test.If we are talking about the same test it requires two known level points putting the transit between them and checking at 180 degrees.My pond test uses the water as a standard of level to check the transit.The bubble level is accurate if it is set correctly.I deal with water on all my jobs so I use the pond to check the transit.I see not everyone agrees with my method and thats ok.It works great for me.
     
  16. D6c10K

    D6c10K Senior Member

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    The two-peg test will tell you what you've got...it doesn't require the two points to be at equal elevations. It's a pretty simple check only requiring two set-ups and maybe a 100' tape.

    Here's a decription I found online...
    http://www.hsc.csu.edu.au/construction/other_units/compulsory/levelling/3349/two_peg_test.html

    Accuracy is a very relative term...depends on what you are trying to do. The instrument you have may be fine for your work and your waterline check may be sufficient for your needs. That said, you have to know the instruments limitations. A transiting level such as yours is highly dependant on the precise adjustment of the bubble...It's not an automatic level with compensators so don't expect it to do extremely precise work...for example, I wouldn't use it to run in a benchmark that required several turning points.
     
  17. td25c

    td25c Senior Member

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    I see what you mean D6c10k about the two-peg test.I guess I could move my transit To another position and check the water level around the pond again.I agree most people dont take time to get a precise adjustment of the bubble.I am confident with it's accuracy after I check it around the waters edge of the pond.