[Qgis-user] True North

Wed Apr 4 09:41:06 PDT 2018

Okay, great. That is very helpful, I will work in the map composer. I know
what you are referring to there. Thanks again...

Cheers . . . . .   Spring
Samsung Tab 4
On Apr 4, 2018 9:36 AM, "Kristian Evers" <kreve at sdfe.dk> wrote:

> I made it within the Layout Composer/Editor (what it’s called in QGIS3
> escapes me now – it used to be Map Composer in 2.x). That was the simplest
> way to achieve it quickly I found. You have the possibility to add more
> than one graticule and you can also change the CRS of the graticule. That
> is what I did. One was kept in UTM, the other used my custom Mercator CRS.
>
>
>
> This is just one way of doing it. There many ways to achieve the same
> thing, but this should outline the general idea at least.
>
>
>
> My last post was not let through to the mailing list, so here’s a copy of
> the image I attached in the previous mail. Should anyone be interested…
>
>
>
> /Kristian
>
>
>
>
>
> *Fra:* Springfield Harrison [mailto:stellargps at gmail.com]
> *Sendt:* 4. april 2018 16:19
> *Til:* Kristian Evers <kreve at sdfe.dk>
> *Cc:* qgis-user <qgis-user at lists.osgeo.org>
> *Emne:* Re: SV: [Qgis-user] True North
>
>
>
> Right, this looks promising.
>
> I have been changing projections and then enabling the grid decoration
> which is always oriented straight up regardless of the projection.
>
> I assume that you were inserting your grids as a vector feature using a
> drawing tool?
>
> What was the CRS of the grid layer? I have been changing the project
> projection with OTF on. Maybe I should be adjusting the projection of the
> layer in question?
>
> Thanks again . . .
>
> Cheers . . . . .   Spring
> Samsung Tab 4
>
> On Apr 4, 2018 5:23 AM, "Kristian Evers" <kreve at sdfe.dk> wrote:
>
> I had a quick go at it after I wrote the email. What I did was to first
> create a custom projection with the proj-string “+proj=merc”. Then I opened
> the layout editor, inserted my map and added to sets of grid lines to the
> map. One of them was left with the original CRS (the UTM one) and for the
> other I used my custom CRS. This immediately gave me two grids, one where
> the meridians is oriented at the grid north (black in the attached image)
> and one oriented at true north (red in the attached image).
>
>
>
> /Kristian
>
>
>
> *Fra:* Springfield Harrison [mailto:stellargps at gmail.com]
> *Sendt:* 3. april 2018 22:52
> *Til:* qgis-user at lists.osgeo.org; Kristian Evers <kreve at sdfe.dk>
> *Emne:* Re: [Qgis-user] True North
>
>
>
> OK, that sounds like the solution I'm looking for.
>
> It sounds like the answer is to draw the lines in one projection and then
> transform it to the other, depending upon which orientation is desired for
> those lines.
>
> I hope I have this correct…
>
> Cheers . . . . . Springfield Harrison
>
>
>
> On 03-Apr-2018 02:46, Kristian Evers wrote:
>
> You can use the Mercator projection to digitize true north lines. It is
> conformal and thus preserves angles. The meridian convergence is 0 (that
> is, true north == grid north) all over the map. If you then transform those
> lines to your chosen CRS you should have a set of lines pointing towards
> true north instead of grid north.
>
>
>
> /Kristian
>
>
>
> *Fra:* Qgis-user [mailto:qgis-user-bounces at lists.osgeo.org
> <qgis-user-bounces at lists.osgeo.org>] *På vegne af *Alexandre Neto
> *Sendt:* 3. april 2018 11:15
> *Til:* Springfield Harrison <stellargps at gmail.com> <stellargps at gmail.com>
> *Cc:* qgis-user <qgis-user at lists.osgeo.org> <qgis-user at lists.osgeo.org>
> *Emne:* Re: [Qgis-user] True North
>
>
>
> 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
>
>
> _______________________________________________
> Qgis-user mailing list
> Qgis-user at lists.osgeo.org
> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>
> --
>
> 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
>
>
>
> [image: Billede fjernet af afsender.]
> <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
>
> Virus-free. www.avg.com
> <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
>
>
>
> _______________________________________________
>
> Qgis-user mailing list
>
> Qgis-user at lists.osgeo.org
>
> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
>
> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20180404/bdfe2280/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.jpg
Type: image/jpeg
Size: 350 bytes
Desc: not available
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20180404/bdfe2280/attachment.jpg>