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lazer level accuracy

loveahammer | Posted in Tools for Home Building on December 25, 2004 05:40am

I have always used optical lense builder’s levels (for framing).  It seems that a laser level (higher quality) would make sense.  One man operation, no confusion with partners, etc.  My concern is that even  the professional  models state “1/4  inch accuracy at 100ft”.  This doesn’t seem that good to me.  I wouldn’t be happy with “1/4 inch at 100 ft” with a standard level.  Should I save my money?

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  1. User avater
    Canabuild | Dec 25, 2004 05:54am | #1

    1/4 inch at 100 feet is the extreme. Most quality lasers are super accurate and reliable. Our laser says the same thing in the manual, and it is bang on everytime.

    This might just be a way for the manufacturer to cover their butts

    1. loveahammer | Dec 25, 2004 06:51am | #2

      I'm glad to hear your laser is "bang on".  It only makes sense that a $300 to $1000 dollar tool should be what you expect.  Their stats did shake my confidence, but they probably have to consider that they have no control over how the tool is set up and used.  Thanks!

      1. User avater
        Bluemoose | Dec 25, 2004 05:25pm | #4

        Many of the lasers in the tool crib magazine have an accuracy of +/- 1/8 at 100 feet. The laser and receiver we use at work has adjustable tolerances so you can vary it depending on how fast/accurate you need to be. (Does that dirt need to be within 3/32?)Does +/- 1/8 mean it could be 1/8 above or below your established grade line giving a total variation of 1/4? Or is the total error 1/8?

        1. moltenmetal | Dec 25, 2004 07:03pm | #5

          +/- 1/8" means a total variation of 1/4" is possible: each time you set the thing up it could read either 1/8" under or 1/8" over plumb at 100'.

          There's not much reasurring about having a bubble to centre- the laser could still be poorly aligned to the bubble.  True, you can calibrate such a unit yourself, if you've got the time, the space and a good water level.  Much tougher to do that with a self-levelling unit...And the water level's not foolproof either- got to make sure it's used properly too.

          I bought a cheap self-levelling cross-line unit at Princess Auto (Canadian equivalent to Harbour Freight).  Referenced to a water level it's about +/- 1/4" at centre of beam at 100 ft, and about +/- 3/8" at 30 degrees off centre.  Good enough for what I'm doing, that's for sure.

        2. User avater
          SamT | Dec 25, 2004 08:04pm | #6

          As far as I know all self levelers work off a gravitational effect. A plumb bob, if you will, however the "Bob" is usually mercury.

          All laser type markers always mark a straight line. Optically straight. any errors in the line will be due to operator error from not following the center or edge of the 'pencil mark'.

          1/4' error in 100' means an accuracy of .02% of the distance from the laser head. All errrors on that line will be the same %, hi or lo, of whatever distance from the head that the measurement is made.

          For instance, set your Laser (1/4" error) up 4' from one end of a 100' wall, and the laser is at max error high. The end of the wall next to the head will be 4' x .02% high. The center of the wall will be 54' x .02% high, and the far end 104' x .02% hi.

          SamT

    2. DonCanDo | Dec 25, 2004 05:22pm | #3

      How do laser levels self-level?  I've been thinking about getting a laser level, but I was planning on getting one with manual leveling.  There's just something re-assuring about setting that little bubble where you want it.  In fact, sometimes, you may not even want level, but prefer to "split the difference".

      I saw a self-leveling laser at the big box for about $20.  Ii worked much like a plumb bob.  I doubt if it was accurate to an inch per foot.  I'm sure the "real" laser levels don't work like this.

      -Don

  2. Sasquatch | Dec 25, 2004 08:17pm | #7

    Get PLS.  You will get 1/8" or better accuracy.  Otherwise, a water level will be perfect.  If you are using a builder's level or a transit, I think it would be difficult to interpret the vials any closer than that anyway.

    Les Barrett Quality Construction
  3. notrix | Dec 25, 2004 08:54pm | #8

    HI,

    I think the acuracy diminishes on distance due to the spread of the beam. My PLS2 has a nice sharp 1/16"+/- in a typical interior. I've used it on walls up to 50-17 feet away and the beam is closer 3/16". (I've only played with this not used nor check accuracy) What I'm guessing is the middle of the beam is pretty close to perfect and how well the operator deals with this the accuracy of final mark.

    PLS makes awsome laser levels. For interior and even out door small jobs (use at dawn or dusk or darker and they are great--PLS2 I refer to) it's an indespensible part of my tool kit.

    Merry Christmas!

    Cor.

    PS I got a cool old new old stock Stanley Pro framer square for Christmas! Just like the common black aluminum but steel...NICE!

    C

  4. FrankB89 | Dec 25, 2004 09:31pm | #9

    For years, I have used a K&E optical machine level that I purchased when one the sawmills I worked in closed.  It is accurate to within .005 at 100'.  We would use it to set machinery and for leveling the rails for headrig log carriages.

    Since my career change to residential construction 12 years ago, I have used it for foundation layout.  It is a fine tool and I take care of it.  But it takes two people and is a little fussy to dial in....but the results are damned near perfect.

    But 3 years ago, I bought a Topcon rotary for foundation layout....about $1200 if I recall...self-leveling and all that.  It's set up for 1/8" at 100'.  I check it occasionally against the old K&E and I have to say, it's remained within 1/16" at 90' (the greatest distance I've had to use it for).  I really love the quick set-up, and you can get the rod really close to it, where the optical level had to be set off at least 12 feet.

    The optical level is easy to verify by doing a 180 degree backline check....as I say, I take care of it and it remains damned near perfect.

    I've rented good quality optical transits in the past, but they were so abused that the results were unrelaiable and disappointing.

    I also have a Berger 300 transit level with stadia that I use when shooting slopes and corners.  It's also a great tool and well-made.

    I built a geodesic dome a couple of years ago and the owner had one of those little lasers with verticals and 90's.  I used it for marking out the plumb lines for partition walls on the ever-changing dome ceiling rather than a plumb bob.  The results were excellent....and the partition walls were absolutely plumb.

    To your question, my view is that the laser technology is a real asset....efficient and accurate. 

     

    1. FrankB89 | Dec 25, 2004 09:47pm | #10

      I posted this awhile back, but here is an antique compass transit-level I scored last year and used it on one job....it's vintage 1918 or so but is still dead-on (though, now, I prefer to keep it retired as a piece of "art": 

  5. ponytl | Dec 25, 2004 10:19pm | #11

    i have a hilti ph15 (or something like) that auto levels... and i have the hand held unit where u can use it in the bright sun...  what i found that you have to watch is it's so dead on that if someone walks near the unit it can affect it ( not on concrete but it's happened on dirt and wood floors) i can set  it in the center of a 150ft sq building and mark all the way around... or use it in a 20ft sq room... always dead on... i got it without a manual so if anyone out there has one they can copy... I know it's a hilti 15  something they no longer make it... but i've enjoyed have'n it..

    pony

    1. rasconc | Dec 26, 2004 07:14am | #19

      http://www.us.hilti.com/holus/modules/techlib/teli_results.jsp?type=instruction_manuals&subtype=measuring

      They list a pr16 on this page for download.

  6. briank | Dec 25, 2004 11:04pm | #12

    I'm not sure what you're building, but I doubt you could find but a handful of residential structures in this country that would be within a 1/4" over 100'.  Given the poor quality of the wood that we are forced to work with, foundation deviations, etc., I'd guess most housed are a 1/4" out of level at like 30'--and this despite the best efforts of the builder.  Your level might say one thing, the excavator's another, etc.

      Our self-leveling rotational lasers use a gyroscope to level themselves.

    1. loveahammer | Dec 26, 2004 05:08am | #18

      Thanks to all for the ideas and input.  Brian, I understand what you are saying about the 1/4" in 100'.  I just try to get my marks as close as I can and have had faith in the optical levels I have had.

  7. Manchild | Dec 26, 2004 12:16am | #13

    I 've wondered at all the self leveling lazer levels coming out. I am a sceptic when it comes to consumer based gadgets that flatter the buyer. You need this because you're such a great he man builder. Ya, right.

    I was wondering if you could check a optical level by marking the height of the beam behind you on something close by, shooting a level say a 100' away, taking the level over to where you shot it, get it to the height of the shot, and then shooting back to the original mark. Wouldn't that double any error over the 100'?

    If when you shot back it was an inch high that would mean you level was high a half inch over 100'.

    1. FrankB89 | Dec 26, 2004 02:19am | #14

      You're in Kansas....flatter than a pancake....shouldn't need a level....:-) 

      1. Manchild | Dec 26, 2004 03:58am | #15

        I did work on a jobsite where the carpenters said they used the horizon of the ocean to site level. what abunch of jokers.

    2. User avater
      jonblakemore | Dec 26, 2004 04:53am | #16

      I think you *could* check a level in that way...
      But the operator error that would be introduced would likely be more than enough to skew your findings.
       

      Jon Blakemore

  8. User avater
    jonblakemore | Dec 26, 2004 04:55am | #17

    I've always thought that a laser is fine if it's accurate to 1/4"/100' or better. If I built a house that was 100' in any dimension and a surveyor verified that it was exactly 1/4" out of level I would be happy. That kind of error just does not show up in our type of work.

    Also remember that the tolerances are the published maximums. I don't konw how the manufacturers statistically derive their figures, but I would bet that a level from a reputable company would be a good bit closer to perfect than the max tolerances.

    BTW, based on the curvature of the earth, a tangent line would have to be 462' long to have a height of 1/16" of an inch above the earth's plane.

     

    Jon Blakemore

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