[QGIS-ZA-user] qgis-za-user Digest, Vol 53, Issue 2

Tue Apr 2 03:27:31 PDT 2024

Hi Jordaan and list,

I found that one of the "best" coordinate conversion tools is at 
https://twcc.fr/en/# where you can convert them manually or from a CSV. 
It also gives you the option of checking if you are in the right place 
with different background maps. You can then use the converted list to 
plot the points in QGIS.

Regards

Immo

On 2024/04/02 11:34, Jordaan Fouche via qgis-za-user wrote:
> Thank you Ryk
>
> Could you please attach the spreadsheet.
>
> I have learnt by now that if I flip the X,Y coordinates and then use EPSG
> 22287 in QGIS, I land up in the correct area (more or less on the correct
> farm). That solution I have learnt from the PlanetGIS documentation. An
> error of 300m should be acceptable for my purpose (for now).
>
> Best regards
>
> Jordaan Fouche
> Portion 11
> Van Reenen Country Estate
> Van Reenen
> 3372
> Republic of South Africa
>
> Tel: +27 (0)82 555 4227
>
> -----Original Message-----
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> qgis-za-user-request at lists.osgeo.org
> Sent: Tuesday, April 2, 2024 11:12 AM
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> Subject: qgis-za-user Digest, Vol 53, Issue 2
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> Today's Topics:
>
>     1. Re: Coordinate conversion from Cape Datum Lo27? to EGS 84
>        (Ryk Taljaard)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 2 Apr 2024 10:32:58 +0200
> From: "Ryk Taljaard"<ryk at boundaryhunter.co.za>
> To: "'South Africa QGIS user group'"<qgis-za-user at lists.osgeo.org>
> Subject: Re: [QGIS-ZA-user] Coordinate conversion from Cape Datum
> 	Lo27? to EGS 84
> Message-ID:<00be01da84d8$5e964640$1bc2d2c0$@co.za>
> Content-Type: text/plain; charset="utf-8"
>
> I use the attached spreadsheet for calculation of CAPE to WGS84
> transformation of coordinate values, for data obtained from specific SG
> diagrams.
>   
> TRIG 1 is the trig beacon closest to the study area and the resulting values
> used for the relevant transformation calculation.
> TRIG 2 is 2nd closest to the study are and used only for indication of any
> possible gross error.
> Take note of:
> (1) The pos/neg switch of coordinate values required for GIS purposes and
> (2) Beware of the study area, TRIG1 and TRIG2 being located in different
> LO-systems.
>   
> Mowbray makes available the localities of all TRIG beacons in KML format, as
> well as the coordinates of all TRIG beacons in both Clarke1880 and WGS84 in
> TXT format, to use as input to the attached spreadsheet.
>   
> Best regards
>   
> Ryk Taljaard
> Boundary Hunter
> Mobile: 082 895 2906
> 1 Joerning Street * Paarl * 7646 * SOUTH AFRICA
> Web:<http://www.boundaryhunter.co.za/>  www.boundaryhunter.co.za  * Email:
> <mailto:ryk at boundaryhunter.co.za>  ryk at boundaryhunter.co.za
>   
> From: qgis-za-user [mailto:qgis-za-user-bounces at lists.osgeo.org] On Behalf
> Of Gavin Fleming via qgis-za-user
> Sent: Tuesday, 02 April 2024 09:51
> To: South Africa QGIS user group
> Cc: Gavin Fleming
> Subject: Re: [QGIS-ZA-user] Coordinate conversion from Cape Datum Lo27? to
> EGS 84
>   
> Hi Jordan and thanks FC
>   
> I?m not sure how FC did the projection / transformation but you can use
> QGIS, proj or a number of other tools.
>   
> An issue to be aware of is that no GIS will do an accurate datum
> transformation from Cape to WGS84/Hartebeeshoek94 since there are different
> errors all over the country, as much as 300m. If you need accuracy, rather
> speak to a land surveyor, who can do a local transformation taking into
> account the known errors.
>   
> Gavin
>
>
>
> On 22 Mar 2024, at 09:25, Jordaan Fouche via qgis-za-user
> <qgis-za-user at lists.osgeo.org>  wrote:
>   
> Thank you FC, what software did you use to do the transformation?
>   
> Could you explain in a bit more detail?
>   
> Jordaan Fouche
> Portion 11
> Van Reenen Country Estate
> Van Reenen
> 3372
> Republic of South Africa
>   
> Tel: +27 (0)82 555 4227
>   
> From: FC Basson<FC.Basson at westerncape.gov.za>
> Sent: Thursday, March 21, 2024 8:26 PM
> To:qgis-za-user at lists.osgeo.org
> Cc:j.fouche9 at gmail.com
> Subject: Re: [QGIS-ZA-user] Coordinate conversion from Cape Datum Lo27? to
> EGS 84
>   
> Just a slight edit to the Google Maps link:
> https://maps.app.goo.gl/VVS9XDfhjp88dXw97
>   
> And if you prefer OSM:
> https://www.openstreetmap.org/?mlat=-26.82808180999955
> <https://www.openstreetmap.org/?mlat=-26.82808180999955&mlon=28.591287809999 
> 518#map=12/-26.8281/28.5913>
> &mlon=28.591287809999518#map=12/-26.8281/28.5913
>   
>   
>    _____
>
> From: qgis-za-user<qgis-za-user-bounces at lists.osgeo.org>  on behalf of FC
> Basson via qgis-za-user<qgis-za-user at lists.osgeo.org>
> Sent: 21 March 2024 20:09
> To:qgis-za-user at lists.osgeo.org  <qgis-za-user at lists.osgeo.org>
> Cc: FC Basson<FC.Basson at westerncape.gov.za>;j.fouche9 at gmail.com
> <j.fouche9 at gmail.com>
> Subject: Re: [QGIS-ZA-user] Coordinate conversion from Cape Datum Lo27? to
> EGS 84
>   
> I was able to locate the farm and can confirm that the coordinate should be
> in LO 29.
> <image001.png>
> For GIS purposes, we use the rotated coordinate system, so the coordinates
> should be X: -40600, Y: -2968350, which converts to geographic coordinate of
> Lat: -26.828082, Lon: 28.591288, if you assume the input datum is Cape.  And
> here is a link to the location in Google Maps:
> https://maps.app.goo.gl/bEwU4pMa35Db2gpNA
>   
> Regards
>   
> FC Basson
>   
>   
>    _____
>
> From: qgis-za-user<qgis-za-user-bounces at lists.osgeo.org>  on behalf of
> Jordaan Fouche via qgis-za-user<qgis-za-user at lists.osgeo.org>
> Sent: 21 March 2024 17:14
> To:qgis-za-user at lists.osgeo.org  <qgis-za-user at lists.osgeo.org>
> Cc:j.fouche9 at gmail.com  <j.fouche9 at gmail.com>
> Subject: [QGIS-ZA-user] Coordinate conversion from Cape Datum Lo27? to EGS
> 84
>   
> Have a set of old borehole data that I wish to plot in QGIS.
>   
> They were clearly drilled pre 1994 (Hartebeesthoek) and I am really
> struggling to plot them on QGIS. I suspect they may be Cape Datum.
>   
> The example that I am including is on the farm Rietvley 600 in the Balfour
> district.
>   
> The coordinates are legible as X:2968350;Y: 40600.
>   
> Can somebody please help me.
>   
>   
> Jordaan Fouche
> Portion 11
> Van Reenen Country Estate
> Van Reenen
> 3372
> Republic of South Africa
>   
> Tel: +27 (0)82 555 4227
>   
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-- 

*Immo F. Blecher**
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