[GRASS-dev] m.cogo enhancement suggestion

Anna Petrášová kratochanna at gmail.com
Sun Jan 21 10:30:35 PST 2018


could you create an enhancement ticket (https://trac.osgeo.org/grass/)
and copy your description there, so that we can keep better track of
this issue? Emails get lost...

Thank you,


On Sat, Jan 20, 2018 at 10:21 PM, Garth Fletcher <garth at jacqcad.com> wrote:
> m.cogo converts  sequences of bearing,distance pairs into coordinates
> The bearing entry is in the form "N 52:17:04 W" widely used in survey maps.
> However, many surveys use magnetic bearings which are rotated from
> true geographic North by an angle called the Declination - which itself
> depends on the date and location.
> When working with such data it is first necessary to convert the
> magnetic bearing by adding(subtracting) the Declination as known
> for the date and location of the survey.
> This is tedious when a survey could consist of hundreds of bearings,
> especially when adding a 15° declination "wraps around" a bearing, for
> example, from N 10 E to N 5 W.
> It would be very helpful if one could provide a Declination argument
> to m.cogo which would be added to each bearing.  All that is needed
> in processing is to add the Declination value to the Azimuth and
> handle the special cases of result <0 or >= 360.
> Way above my skill level, but I'm hoping somebody might take an interest.
> Cordially,
> --
> Garth Fletcher
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