[QGIS-ZA-user] South African CRSs in QGIS

Fri Nov 16 03:23:31 PST 2018

Anyone know when this tmerc SA system is to be replaced with UTM as I have
read from a post by Manie Brynard is to happen

On Fri, 16 Nov 2018 11:50 Aslam Parker via qgis-za-user <
qgis-za-user at lists.osgeo.org wrote:

> Hi All
>
>
>
> We had a look at the new CRS's in QGIS 3.4.1.
>
>
>
> Comparatively, the original CRS metadata is (e.g.):
>
>
>
> _________________________________________
>
> Hartebeesthoek94 / Lo19 [EPSG: 2048]    ..... EPSG numbers range from 2046
> - 2055
>
> Extent: 17.99, -34.88, 20.00, -28.38          ...... This varies depends
> on the central meridian
>
> Proj4: +proj=tmerc +lat_0=0 +lon_0=19 +k=1 +x_0=0 +y_0=0 +axis=wsu
> +ellps=WGS84 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs
>
>
>
> These were the official parameters supplied by Chief Directorate: National
> Geospatial Information as indicated in the EPSG metadata. EPSG will not add
> information from non-authoritative sources. In QGIS the values will be
> correctly displayed, but a rotation of 180 deg will have to be applied for
> a North up view, unless there is a way for QGIS to automatically rotate
> view if it detects a south oriented coordinate system. This is regardless
> of what source CRS data you bring into the project as the on-the fly
> conversions works well. Unfortunately not all software is able to deal
> correctly with a left handed system.
>
> These use the correct extent, central meridian, scale factor, reference
> ellipsoid and positive coordinate order and orientation correctly
> identified as wsu. These are the recommended CRS's to use when working in
> Hartbeesthoek94 Projected .
>
>
>
> On a really technical level, the relationship between Hartebeesthoek94 and
> WGS84 is changing and the +towgs84=0,0,0,0,0,0,0 is not true at the sub 1m
> level.
>
> ______________________________________________________________________
>
> The ZANGI:HBK CRS metadata is (e.g.):
>
>
>
> South African CRS : HBK_NO_19 [ZANGI:ZANGI:HBKNO19]
>
> Extent: Extent not known
>
> Proj4: +proj=tmerc +lat_0=0 +lon_0=19 +k=1 +x_0=0 +y_0=0 +axis=enu
> +ellps=WGS84 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs
>
>
>
> The ZANGI:HBK series of CRS's are similar (no extent in the metadata) but
> use a north-east positive axis orientation. This CRS is not consistent with
> the official SACRS and in not recommended. Although it seems that our
> imagery is correctly displayed when overlaying SG data, the displayed
> coordinates magnitude and order is correct, but the sign is opposite. These
> have no EPSG numbers and not recommended for use if you require correctly
> display of coordinate in the SACRS.
>
> ______________________________________________________________________
>
> The new CRS's that have appeared in QGIS have the following metadata
> (e.g.):
>
>
>
> The "EPSG codes" 102480 to 102489 and 102562 to 102568 do not occur in the
> EPSG registry. (https://www.epsg-registry.org/), our guess is that
> someone in the QGIS community has added these in QGIS.
>
>
>
> Hartebeesthoek94_Lo19 [EPSG:102482]
>
> Extent: Extent not known
>
> Proj4: +proj=tmerc +lat_0=0 +lon_0=19 +k=-1 +x_0=0 +y_0=0 +ellps=WGS84
> +units=m +no_defs
>
>
>
> Hartebeesthoek94_Lo19_(E-N) [EPSG:102562]
>
> Extent: Extent not known
>
> Proj4: +proj=tmerc +lat_0=0 +lon_0=19 +k=1 +x_0=0 +y_0=0 +ellps=WGS84
> +units=m +no_defs
>
>
>
> These have no extent information but use the correct central meridians and
> ellipsoid. However, the only difference is the scale factor. As there is no
> reference to the axis orientation, these CRS's probably work in the default
> north-east orientation and control the orientation using the scale factor,
> i.e. the former uses a scale factor of -1 while the latter uses a scale
> factor of 1.
>
>
>
> Hence, the latter (E-N) CRS is north-east orientated and the former seems
> south-west orientated. The EPSG numbers range from 102480 - 102489 for the
> south west orientated CRS's and 102562 - 102568 for the north-east
> orientated CRS's. The use of a -1 scale factor is an incorrect
> implementation to give the impression of a left-handed system.
>
>
>
> ____________________________________________
>
> In summary, we recommend that only the original CRS's (EPSG 2046 - 2055)
> which inherently specify the axis orientation in the metadata and do not
> control the orientation using scale factors be used.
>
>
>
> Perhaps a clean-up is in order and in future we should be notified when
> new CRS's for South Africa are added to the EPSG registry so we can verify
> them.
>
>
>
> Hope this helps.
>
>
>
> Kind regards,
>
>
>
> Cameron van Eck, Patrick Vorster and Aslam Parker
>
>
>
>
>
> *From:* qgis-za-user [mailto:qgis-za-user-bounces at lists.osgeo.org] *On
> Behalf Of *Paul Young via qgis-za-user
> *Sent:* Thursday, 15 November 2018 10:08 AM
> *To:* South Africa QGIS user group
> *Cc:* Paul Young
> *Subject:* Re: [QGIS-ZA-user] South African CRSs in QGIS
>
>
>
> I still have Proj4 ver 4.9.3. but run QGIS 3.4 but I think the repo is
> QGIS not Ubuntu GIS. I suppose I could add the Ubuntu GIS repo into
> /etc/apt/sources.list and run apt-get update and upgrade to get it to 5.2?
>
>
>
> On Thu, 15 Nov 2018 09:17 Tim Sutton via qgis-za-user <
> qgis-za-user at lists.osgeo.org wrote:
>
> Hi
>
>
>
> For those interested, you can see a detailed report on the EPSG codes
> published here (go back to the home page to tweak the search string if
> needed):
>
>
>
>
> http://www.epsg-registry.org/report.htm?type=selection&entity=urn:ogc:def:crs:EPSG::4940&entity=urn:ogc:def:crs:EPSG::4941&entity=urn:ogc:def:crs:EPSG::4148&entity=urn:ogc:def:crs:EPSG::2046&entity=urn:ogc:def:crs:EPSG::2047&entity=urn:ogc:def:crs:EPSG::2048&entity=urn:ogc:def:crs:EPSG::2049&entity=urn:ogc:def:crs:EPSG::2050&entity=urn:ogc:def:crs:EPSG::2051&entity=urn:ogc:def:crs:EPSG::2052&reportDetail=long&style=urn:uuid:report-style:default-with-code&style_name=OGP%20Default%20With%20Code&title=South%20African%20Projections&r=59
>
>
>
>
>
> QGIS uses a little internal application called crssync to populate it’s
> internal CRS database from Proj. Layered on top of that are other CRSes
> that haven’t made their way into EPSG yet. It takes a while for CRS’s to
> make their way into EPSG -> Proj -> QGIS. The ZANGI definitions were QGIS
> specific definitions that Gavin and I cooked up in the absence of these
> CRS’s being in EPSG and Proj. Please let us know if the ones provided in
> Proj 5 now deprecate the ZANGI and I will remove them from QGIS’s CRS
> database. We hope to eventually remove the need for QGIS’ own layer on top
> of the Proj database. Even (proj maintainer) has been talking about moving
> proj’s CRS database to a sqlite database so in theory we could just have
> one database that is shared between, proj, gdal, QGIS etc. which would make
> things more consistent.
>
>
>
> BTW Mac users are also still getting Proj 493 in the official Mac packages.
>
>
>
>
>
> Happy QGISsing :-)
>
>
>
> Regards
>
>
>
> Tim
>
>
>
> On 15 Nov 2018, at 08:52, Immo Blecher via qgis-za-user <
> qgis-za-user at lists.osgeo.org> wrote:
>
>
>
> Morning Frank,
>
> This is exactly the one I am using but it has proj 493. I will do a
> complete removal and install again, maybe some older files remain due to
> dependencies?
>
> Thanks for all your help.
>
> Regards
>
> Immo
>
> On 2018/11/14 08:37, Frank Sokolic via qgis-za-user wrote:
>
> Hi Immo,
>
>
>
> This is the repository I'm using:
>
> deb https://qgis.org/ubuntu cosmic main
>
>
>
> When I install QGIS 3.4 from this repository it loads Proj 5.1.0 which
> contains the CRSs I listed in my earlier post.
>
>
>
> Frank.
>
>
>
> On 2018/11/14 07:58, Immo Blecher via qgis-za-user wrote:
>
> Good Morning,
>
> I think the "latest" proj4 probably sits with the ubuntugis-unstable
> version. And I am on Ubuntu 18.04 LTS, which apparently does not support
> the latest ubuntugis-unstable. Or did anybody get it installed and working?
>
> Regards
>
> Immo
>
> On 2018/11/13 19:16, Paul Young via qgis-za-user wrote:
>
> Hi there I tried to pul the Docker Proj4 and it would not upgrade.
>
>
>
> It gave: Rel. 4.9.3, 15 August 2016
>
> Maybe it needs to be compiled from source?
>
>
>
> [image: Description: Image removed by sender.]
>
> On Tue, 13 Nov 2018 at 12:24, Immo Blecher via qgis-za-user <
> qgis-za-user at lists.osgeo.org> wrote:
>
> Hi Frank,
>
> That is weird! I am on 3.4, but installed from the Debian link, not the
> ubuntugis as there I had dependency issues. Maybe there is still a big
> difference between the two. But I will try the ubuntugis route again. The
> proj version obviously makes all the difference.
>
> Regards
>
> Immo
>
>
>
> On 2018/11/13 12:20, Frank Sokolic via qgis-za-user wrote:
>
> Hi Immo,
>
>
>
> Not sure why they don't show up for you. I can see them on QGIS 3.14 and
> the Proj version is 5.1.0. This is on Ubuntu Linux.
>
>
>
> Regards, Frank.
>
>
>
> On 2018/11/13 11:31, Immo Blecher via qgis-za-user wrote:
>
> Hi QGIS Users,
>
> I can't find these in my QGIS 3.4. And I see that Proj4 is still on
> version 4.93, but the latest seems to be 5.2.
>
> But what I also noticed is that Proj4 changed the way it converts from/to
> Hartebeesthoek94 (15 to 31) from version 4.7 to vers. 4.9: Using proj4 4.7
> to convert one had to turn around E-W and N-S, w.o.w. X = -X and Y = -Y and
> then convert. From vers. 4.9 this was not necessary any longer so I think
> the calculations in QGIS should be sorted out (it is actually a bug and
> that is why everything is upside down and right=left). That would also mean
> that we would not need the ZANGI:ZANGI projections any longer but just use
> the built-in Hartebeesthoek94 ones.
>
> For what it's worth!
>
> Immo
>
> On 2018/11/13 10:58, Frank Sokolic via qgis-za-user wrote:
>
> Hi QGIS users,
>
> I noticed last week that these CRSs have appeared in QGIS under Project
> Coordinate Systems > Transverse Mercator:
>
> EPSG:102480 Hartebeesthoek94_Lo15
> EPSG:102481 Hartebeesthoek94_Lo17
> EPSG:102482 Hartebeesthoek94_Lo19
> EPSG:102483 Hartebeesthoek94_Lo21
> EPSG:102484 Hartebeesthoek94_Lo23
> EPSG:102485 Hartebeesthoek94_Lo25
> EPSG:102486 Hartebeesthoek94_Lo27
> EPSG:102487 Hartebeesthoek94_Lo29
> EPSG:102488 Hartebeesthoek94_Lo31
> EPSG:102489 Hartebeesthoek94_Lo33
> EPSG:102562 Hartebeesthoek94_Lo19_(E-N)
> EPSG:102563 Hartebeesthoek94_Lo21_(E-N)
> EPSG:102564 Hartebeesthoek94_Lo23_(E-N)
> EPSG:102565 Hartebeesthoek94_Lo25_(E-N)
> EPSG:102566 Hartebeesthoek94_Lo27_(E-N)
> EPSG:102567 Hartebeesthoek94_Lo29_(E-N)
> EPSG:102568 Hartebeesthoek94_Lo31_(E-N)
>
> Anyone know anything about them? Are these now the official South African
> CRSs in the EPSG database? If so, where are L015_(E-N), L017_(E-N) and
> L033_(E-N)?
>
> With these new additions, there are now a few versions of the South
> African CRSs in the QGIS CRS database (e.g. EPSG 2046 to EPSG 2055 as well
> as ZANGI:HBKNO15 to ZANGI:HBK033) so I guess things need to be cleaned up.
>
> Regards, Frank.
>
> _______________________________________________
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> * Street: **36 Saffraan Ave., Die Boord, Stellenbosch, 7613, South Africa*
> *Postal: PO Box 74, Lynedoch, 7603, South Africa*
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>
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> *Postal: PO Box 74, Lynedoch, 7603, South Africa*
> *Cell: * +27 83 272 6791 | *Fax: *+27 86 736 3302 *Email:*
> immo at blecher.co.za | immob19 at gmail.com |
> *immob at mymtnmail.co.za <immob at mymtnmail.co.za> **Internet:*
> http://www.blecher.co.za/
>
> Contact me: [image: Description: Image removed by sender.]
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>
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>
> Paul Young
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> --
>
> *Immo F. Blecher*
> * Street: **36 Saffraan Ave., Die Boord, Stellenbosch, 7613, South Africa*
> *Postal: PO Box 74, Lynedoch, 7603, South Africa*
> *Cell: * +27 83 272 6791 | *Fax: *+27 86 736 3302 *Email:*
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> *immob at mymtnmail.co.za <immob at mymtnmail.co.za> **Internet:*
> http://www.blecher.co.za/
>
> Contact me: [image: Description: Image removed by sender.]
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>
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> --
>
> *Immo F. Blecher*
> * Street: **36 Saffraan Ave., Die Boord, Stellenbosch, 7613, South Africa*
> *Postal: PO Box 74, Lynedoch, 7603, South Africa*
> *Cell: * +27 83 272 6791 | *Fax: *+27 86 736 3302 *Email:*
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> *immob at mymtnmail.co.za <immob at mymtnmail.co.za> **Internet:*
> http://www.blecher.co.za/
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>
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> —
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>
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>
> *Tim Sutton*
>
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>
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