Finding Bearing and Distance using Calculator?

  1. ∆Eastings + 262.575
    ∆Northings + 929.573

    Bearing = not an idea how to work it out

    Distance = Pol(∆Northing,∆Easting)= displays distance

    Please help, thanks!
     
  2. jcsd
  3. I have no Idea how your calculator might work. Apparently the Pol() function converts an x and and y distance in polar coordinates. A second number should be produced that gives the bearing.
     
  4. mgb_phys

    mgb_phys 8,952
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    Have you heard of tan()?

    Take a look at arctan or better atan2
     
  5. I'm completely new to my professional practice course and we have been given a presentation to do from scratch so I'm learning from the very bottom despite it being University work, I have never done this before.

    tan-1 (1662.275)/893.463 = 0.1001

    How does this convert into a bearing, presuming this is the right method to use.
     
  6. mgb_phys

    mgb_phys 8,952
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    ok - don't worry surveying is all just junior school maths really.

    Firstly get used to drawing some diagrams - and get some graph paper.
    Then a couple of gotcha's:
    Surveying uses Northing and Easting rather than X and y. Northing is up the page = Y and Easting is to the right = X.
    Angles are measured clockwise from north.

    So to get the bearing you just draw an N(up) and E(to the right) axis.
    The point is at 262 units across and 929 units up.
    Draw a line back to the origin.
    You are looking for the angle this line makes with the north axis (ie up the page)

    Remember
    sin = opposite/hypotenuse
    cos = adjacent/hypotenuse
    tan = opposite/adjacent

    You know the distance opposite the angle (it's the same as the distance along the East axis) and the distance adjacent to the angle (it's the distance up the North axis)

    So tan(bearing) = easting / northing
    or atan(easting / northing) = bearing

    The length of the line you can get from the same trig or from pythagorus

    Apart from having to deal with deg/min/sec that's about all there is to it - except for holding a survey pole steady and not dropping the theodolite.
     
  7. Sadly I need to know deg/min/sec too, if that is something like 317° 40’ 44”
     
  8. mgb_phys

    mgb_phys 8,952
    Science Advisor
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    Simple enough
    there are 60mins in a degree and 60secs in a minute

    So to convert dms to deg
    deg = deg + min/60 + sec/(60*60)

    To convert deg back to dms.
    deg = just take the whole number.
    Then multiply the decimal part by 60 = the minutes are the whole number
    Then multiply the decimal of that by 60 = the seconds are the result

    eg 1deg 10min 20sec
    = 1 + 10/60 + 20/3600 = 1.1722

    1.1722 = take whole part = 1 deg
    0.1722 * 60 = 10.333, take whole part = 10 mins
    0.333 * 60 = 20.0 = the seconds

    there is probably a button on your calculator to do this for you
     
  9. I seriously can't thank you enough. You've certainly bumped my grade up with that, so thank you very much.

    So if you had

    26° 12’ 48”
    172° 23’ 08”

    How would you work out horizontal angle? I already know the answer is 146° 10’ 20” just not sure how to get to it.

    Last question, promise as I'm nagging now :)
     
    Last edited: Mar 22, 2010
  10. I seriously can't thank you enough. You've certainly bumped my grade up with that, so thank you very much.

    So if you had

    26° 12’ 48”
    172° 23’ 08”

    How would you work out horizontal angle? I already know the answer is 146° 10’ 20” just not sure how to get to it.

    Last question, promise as I'm nagging now :)
     
  11. mgb_phys

    mgb_phys 8,952
    Science Advisor
    Homework Helper

    26° 12’ 48” --> 172° 23’ 08”

    end - start = 172° 23’ 08” - 26° 12’ 48” = 172.3855 - 26.2133 = 146.1722 = 146° 10' 20"
     
  12. Anyone know how to display the bearing (deg/min/sec) with the Northing and Easting?
     
  13. Javascript geodetic azimuth distance/bearing Calculator:

    http://mysite.verizon.net/weltwireless/tech/distance_bearing.htm

    mysite.verizon.net/weltwireless/tech/distance_bearing.htm

    This calculator is based on "Vincenty's Formula" for elliptical Earth. It is not based on the "Great circle formula" which is innacurate and assumes a "round" Earth.
    Comprises two programs essentially the same as INVERSE & FORWARD available at National Geodetic Survey.
    INVERSE - computes the geodetic azimuth (bearing) and distance between two points, given their geographic positions. FORWARD - computes the geographic position of a point, given the geodetic azimuth (bearing) and distance from a point with known geographic position.

    Calculate the geodetic azimuth and distance between two points (Inverse)
    Enter lat/long. of two points, select distance units and Earth model and click "compute".

    Note that if either point is very close to a pole, the course may be inaccurate, because of its extreme sensitivity to position and inevitable rounding error.
     
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