[Qgis-user] True North

[Alexandre Neto]

Maybe something like this :

https://gis.stackexchange.com/q/115531/6191

Alexandre

A ter, 3/04/2018, 10:11, Alexandre Neto <senhor.neto at 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 <stellargps at 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.neto at 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 <stellargps at 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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>>>
>>> --
>>> Alexandre Neto
>>> ---------------------
>>> @AlexNetoGeo
>>> http://sigsemgrilhetas.wordpress.com
>>> http://gisunchained.wordpress.com
>>>
>> --
> Alexandre Neto
> ---------------------
> @AlexNetoGeo
> http://sigsemgrilhetas.wordpress.com
> http://gisunchained.wordpress.com
>
-- 
Alexandre Neto
---------------------
@AlexNetoGeo
http://sigsemgrilhetas.wordpress.com
http://gisunchained.wordpress.com
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