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  1. #16
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    Feb 2003
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    Default

    Quote Originally Posted by yakka View Post
    I usually use diagonals or 3m - 4m - 5m formula to square up.. My question is what methods do you use over large areas e.g.: 40 x 30m to ensure you get a nice perfectly set rectangle
    <O</O


    Cheers yakka
    define "perfectly set rectangle"
    how much "out of square" error can you tollerate?

    and before you answer, can you tell if the area you want to plant the rectangle is on level?

    if you have a spring balance and a 50m steel or cloth tape, you can set out the rectangle because just like the 3:4:5 triangle
    30 squared + 40 squared = 50 squared (900 + 1600 = 2500 = 50x50)
    important points
    • both ends of the tape must be at the same level which is not the same as the same distance off the ground
    • the tape must not touch the ground anywhere
    • all measurements must be made with the same reading on the spring balance
    • lay out the 40m long side
    • then from one end lay out the 30m side, drawing an arc on the ground roughly where the corner should be
    • lay out the 50m diaganal – where the diaganal intersects the arc, is where the corner is
    • repeat for the 4th corner
    if you need to be accurate to a few cms you'll need to correct for temperature and hiring a surveyor is probably the easiest option.
    Especially so if the site isn't level or if the layout is for a prefab shed.


    ian

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  3. #17
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    Oct 2006
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    Tallahassee FL USA
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    Default

    I was going to just postscript a suggestion to measure at night to reduce temperature effects. But a further question arises: To paraphrase ian, how "perfect" does it have to be? Most structures should have some local adjustment built into the design. Large equipment such as newspaper printing presses, long-line machining centers and such come to mind. In such a case, a surveyor would be mandatory.

    In an earlier career in the precast architectural concrete game, we always allowed a minimum of 25mm clearance to anything we didn't control, such as the building frame, and made up the gaps in the connection design. Then for the odd-ball cases, we made the specials to fit after the main parts had been erected.

    Joe
    Of course truth is stranger than fiction.
    Fiction has to make sense. - Mark Twain

  4. #18
    Join Date
    May 2003
    Location
    Kuranda, paradise, North Qld
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    Default

    Like TeeJay says, it depends what degree of accuracy you're after. I've only ever used profiles, stringlines and tapes. Unless your building something like a hospital or a shopping centre you don't need to get any more accurate than this will allow.

    Mick
    "If you need a machine today and don't buy it,

    tomorrow you will have paid for it and not have it."

    - Henry Ford 1938

  5. #19
    Join Date
    Feb 2006
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    melbourne
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    14

    Default

    guys- further to what Ian said- the hypotenuse (A) is the square root of sum of X and Y squared (see sheet attached) just change the numbers for your dimensions.

  6. #20
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    Oct 2003
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    Kentucky NSW near Tamworth, Australia
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    Default

    Like Mick and Al says if it is for a prefab shed using the profiles is all that is necessary and set out the first corner with the 3, 4, 5 method and then just measure the diagonals using a steel tape.

    This was how we set out sheds and there is enough tolerance in them to allow for minor discrepancies and 30 x 40 metres is not that big really and if it was a shed being built on a slab the ground would have been leveled first.

    Our guys used to set out piers for sheds with the ground up to 1200mm out of level over 40 metres.

  7. #21
    Join Date
    Jul 2003
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    On the Downs, Darling SEQld
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    1,167

    Default Not Fair

    Quote Originally Posted by Chesand View Post
    5, 12, 13 also works. 5 & 12 are the sides, 13 the hypotenuse if it is sqaure
    Chesand,
    You took the easy one:mad:
    OK
    9, 40, and Hyp is 41

    Wanna be a mighty long piece of Timber
    Navvi

  8. #22
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    Oct 2003
    Location
    Kentucky NSW near Tamworth, Australia
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    Default

    For those that have Microsoft Excel here is a Hypotenuse Calculator.

  9. #23
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    139

    Default

    If you want to use the square root method (see Cyberhonky’s post above), then using the cell references in Bazza’a Excel model, the Excel formula for the Hypotenuse is:

    =SQRT((POWER(F15,2)+POWER(I11,2)))

  10. #24
    Join Date
    Nov 2004
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    Sydney
    Age
    59
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    84

    Default

    why not do it of a night and use the stars !:eek:
    Thinking about mowing the lawn doesn`t get it done !

  11. #25
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    Jan 2004
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    Over there a bit
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    17
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    2,511

    Default

    Quote Originally Posted by Vernonv View Post
    Other than for cropping (mainly), there aren't too many farmers around that have/use high accuracy positioning systems.

    I'm always amazed at the number of people (not just farmers) that expect their $200 GPS received to be accurate to the metre (or sub-metre).

    Even the 5 metre accuracy most receivers quote in nearly impossible to achieve under normal usage conditions.
    Ya gotta understand these farmers are after -2.5cm accuracy. Probably less than most shopping centres. Yes, for cropping only, but thats prestty impressive for 1000 acres. :eek:
    Boring signature time again!

  12. #26
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    back in Alberta for a while
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    Default

    Quote Originally Posted by John99 View Post
    why not do it of a night and use the stars !:eek:
    I take it you have an atomic clock and a transit telescope

  13. #27
    Join Date
    Jul 2003
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    On the Downs, Darling SEQld
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    1,167

    Talking Night

    Quote Originally Posted by John99 View Post
    why not do it of a night and use the stars !:eek:

    Why not do it at night and you will have difficulty in seeing any errors:eek:
    No Stars and
    you will have difficulty in seeing anything much at ALL
    Navvi

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