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  • Fore bearing and Back Bearing Confusion, Please help

    ErAnushka

    Member

    Updated: Oct 27, 2024
    Views: 1.3K
    Fore Bearing - Back Bearing = 180?

    OR
    Back Bearing - Fore Bearing = 180.

    I fully understood the concept of meridian and bearing 😀

    😲 But this thing is little confusing, as far as I know, Back Bearing - Fore Bearing should be 180, but I read somewhere that, Fore Bearing - Back Bearing = 180, but if you imagine, FB-BB would be negetive!

    and let's say we have ABCD traverse,
    Now, Let's start with line AB,
    Back bearing of AB line - Fore bearing of AB line = 180,

    But if we go further and take the line DA,
    Fore Bearing of DA - Back Bearing of DA = 180,


    Now I don't understand, why some people fixed FB-BB = 180?
    or my imagination is wrong ? What's the correct method and principle?

    Please explain me 😕
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Replies

  • Saiwal

    Member • Sep 25, 2012

    there is no absolute relation between the forebearing and backbearing.
    Depending on the survey direction and location of north the following relation exists:
    Fore bearing = Back bearing ± 180°
    or
    Back Bearing = Fore Bearing ± 180°

    thus both your arguments are true.
    refer: #-Link-Snipped-#
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  • Jeffrey Arulraj

    Member • Sep 25, 2012

    We just use each one when the other is more than !80

    If FB=350 then BB=FB-180=170

    And if BB =350 then FB=BB-180=170
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  • ErAnushka

    Member • Sep 25, 2012

    Saiwal
    there is no absolute relation between the forebearing and backbearing.
    Depending on the survey direction and location of north the following relation exists:
    Fore bearing = Back bearing ± 180°
    or
    Back Bearing = Fore Bearing ± 180°

    thus both your arguments are true.
    refer: #-Link-Snipped-#
    You saved my day! ☕ Thank you ^_^
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  • ErAnushka

    Member • Sep 25, 2012

    jeffrey samuel
    We just use each one when the other is more than !80

    If FB=350 then BB=FB-180=170

    And if BB =350 then FB=BB-180=170
    I got it ^_^ Thank you 😀
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  • Jeffrey Arulraj

    Member • Sep 26, 2012

    Most welcome pal
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  • Rock Rohit

    Member • Oct 13, 2015

    If fb is 145 then what will be the BB
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