OK, thank you. That formula is useful.
I assume that "North" for any projection will be grid North so that a
line drawn at 0° while using a UTM projection will point to grid North
if the drawing is re-projected using an un-projected CRS (where 0° is
true North)?
I wonder if I have that correct? I will check some of the other
responses also.
Thanks very much…
Cheers . . . . . Spring Harrison
On 03-Apr-2018 02:15, Alexandre Neto wrote:
Maybe something like this :
https://gis.stackexchange.com/q/115531/6191
Alexandre
A ter, 3/04/2018, 10:11, Alexandre Neto <senhor.n...@gmail.com
<mailto:senhor.n...@gmail.com>> escreveu:
Ah sorry,
I got lost in translation. You are right, I was talking about the
magnetic north, not the geodetic one.
Meanwhile, remembering that all UTM are Transverse Mercator, I
don't think there's a CRS that will solve you question.
I think you need to use some formula to convert the grid north
measures to true north according to the CRS, and the latitude and
longitude of the place.
Alexandre
A ter, 3/04/2018, 09:25, Springfield Harrison
<stellar...@gmail.com <mailto:stellar...@gmail.com>> escreveu:
Alexandre,
I believe that true north is actually a constant oriented
towards the North Pole, i e 90 degrees north latitude. Also
where all meridians converge in the northern hemisphere.
The other North orientations are magnetic north and grid North
and these do vary as you suggested.
I do need to use a UTM projection but need bearings to be in
degrees true north.
Thanks Alexandre...
Cheers . . . . . Spring
Samsung Tab 4
On Apr 2, 2018 4:27 PM, "Alexandre Neto"
<senhor.n...@gmail.com <mailto:senhor.n...@gmail.com>> wrote:
AFAIK, true bearing differs in time and location because
of magnetic declination. So I don't think there is a such
thing as a CRS with true bearings.
Assuming you are working at regional level, find the
magnetic declination for that region and remove it from
your observations. Then draw the azimuth using the chosen
CRS. I think 26910 will work just fine.
If you are at a larger scale, then you may need to use
different magnetic declination values for each observation.
This may help:
https://www.ngdc.noaa.gov/geomag/declination.shtml
Best Regards,
Alexandre Neto
A seg, 2/04/2018, 23:54, Springfield Harrison
<stellar...@gmail.com <mailto:stellar...@gmail.com>> escreveu:
Hello,
I am using CRS 26910, NAD83 / UTM zone 10N, and need
to draw lines at
exact true bearings. The Advanced Digitizing Tool
seems to do this but
which CRS would I use to ensure that the bearing is True?
Thanks very much . . .
Cheers . . . . . Springfield Harrison
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