Entering COGO points that don't follow the help

George Chandeep CoreaGeorge Chandeep Corea Global Mapper UserPosts: 62Trusted User
I am trying to interpret the attached drawing and can't figure out how to do it as the values don't match with any of the examples in the global mapper help system. How can I do this? The PSM it refers to is http://qspatial.information.qld.gov.au/SurveyReport/SCR114207.pdf
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Best Answer

  • MykleMykle Global Mapper User Posts: 382
    Answer ✓
    Your PDF file has a lot of information included on the first page.  Bearings, distances, reference numbers, etc.
    The Bearings appear to be shown as 25d39'25" where "d" is the degree symbol.

    A bearing may refer to one line segment (between two intersections marked with a small circle), or it may refer to several segments of a line through more than one intersection.  The example here is shown as the line running NorthEast from Point 1, and it extends to a line bend marked with a small "4".
    The distance from Point 1 to the first intersection (marked with a small "2") is "277.64", and the total distance is shown as "(408.04)".  The note above the bearing is "(1-4)" that looks like it is documenting that the bearing and total distance is for the line segments between points 1 and 4. 

    The second sheet does not have bearings, just coordinates of each point and distances between points. 
    The space in each value appears to just be a visual aid like a comma, so the value is the entire number, like E 513,764.74.  People using this diagram are more concerned with the last part of the number (764.74), but the complete value is included.   For a similar example, look in the Explanatory Notes at the bottom, at the line scale factor that is one number shown with spaces for clarity. 

    I typed the coordinates for all twelve points into a simple text file, and imported it into Global Mapper, using WGS84, UTM zone -54, meters.  The zone -54 signifies zone 54, southern hemisphere.  The notes specify MGA94.  Not seeing that in Global Mapper, I simply used WGS84.  For your purposes, you will need to figure out how to specify MGA94 since the coordinates were recorded with a RTK system (potentially accurate to less than a centimetre).  So there is likely to be a shift between WGS84 and MGA94, however small.  I then exported the data into a Google Earth KMZ file, and imported it to see that it covers a river at a construction site for a weir or bridge near Glenore.  It is more likely to be a weir since there is a perfectly good highway bridge just downstream. 

    Here is the file of points:
    Easting   Northing   Point
    513784.74 8025336.19 1
    513455.42 8024708.22 2
    513281.05 8024722.53 3
    512901.72 8023479.79 4
    511595.41 8022778.14 5
    511871.29 8022250.10 6
    512961.49 8022813.60 7
    513165.69 8022736.62 8
    513742.96 8023673.11 9
    513755.34 8024780.03 10
    513889.27 8025058.86 11
    513931.94 8025147.68 12


Answers

  • bmg_bobbmg_bob Global Mapper Programmer Posts: 1,686
    Hello,

    It appears that you ought to be able to use the first option, Specify Separate Distance and Bearing Values, since the PDF contains tables of bearing and distance.  In addition, you might also want to use the DMS (degree/minute/second) Values Specified in Decimal Degrees option so you can enter DM (degree/minute) or DMS (degree/minute/second) values as decimal degrees. For example with this option checked, a value of 40.3020 is interpreted as 40 degrees, 30 minutes, and 20 seconds. The basic format of degree fields when this option is checked is DD.MMSS.

    Cheers,
    Bob
  • George Chandeep CoreaGeorge Chandeep Corea Global Mapper User Posts: 62Trusted User
    So when it has point 1 - E513 764.74 and N8025 336.19 , how do I interpret this? E513 can't be an angle? it could be E51.376.74 but this is northern Australia so that Easting makes no sense. The PSM it's based off is 
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