[OSGeo Africa] Identify coordinate system

[Tim Sutton]

Hi

Also consider that some countries (e.g. UK) use a false easting and northing so that the CRS origin starts from 0,0 just outside the sovereign territory….

Regards

Tim

> On 12 Jul 2019, at 08:11, Zoltan Szecsei <zoltans at geograph.co.za> wrote:
> 
> Hmmm....Ja.
> But querying the source of the data might save all of us from getting a hard-earned 'Sherlock Holmes' badge :-)
> 
> On 2019/07/12 10:02, Hermanus Brynard wrote:
>> Zoltan
>> You mention 500k makes me think there could be a UTM transformation which usully adds a 500000m easting or westing and 10 000 000m northing to avoid negative numbers.
>> 
>> Can you send me the shapefile.
>> Manie
>> 
>> 
>> On Fri, Jul 12, 2019 at 8:57 AM Zoltan Szecsei <zoltans at geograph.co.za <mailto:zoltans at geograph.co.za>> wrote:
>> Hi Manie,
>> Thanks for the idea.
>> 
>> The current system in use is QND95 - the one you are suggesting  (I see) is from 1976, and its origin is "too close".
>> (Yes, I still tried it)
>> 
>> Looking at the numeric values of the coords, I am expecting something with an origin some 500Km West of Doha, and on the Equator.
>> 
>> And then of course I also need to consider the possibility that the coords in the shapefile are non-sensical, so I'm trying to find out its source....
>> 
>> 
>> Thanks and keep well,
>> Zoltan
>> 
>> On 2019/07/12 09:23, Hermanus Brynard wrote:
>>> Zoltan
>>> Have you tired the 
>>> 
>>> Quatar National Grid  <https://epsg.io/28600>
>>> EPSG:28600 <https://epsg.io/28600>
>>> 
>>> Manie Brynard
>>> 
>>> On Thu, Jul 11, 2019 at 6:33 PM Zoltan Szecsei <zoltans at geograph.co.za <mailto:zoltans at geograph.co.za>> wrote:
>>> Hi Listers,
>>> I've been asked o help a school-going daughter of a friend of mine in Doha (yes, this is "AfricaList" :-/  )
>>> She has been given a shapefile without a projection file. The area is Al Wakrah, just South of Doha airport.
>>> 
>>> The numeric values of the geometry coords are around 560000, 2782000 - the second value looked like a distance from the Equator, so I tried UTM 39N
>>> The scaling seems wrong, and it does not align with the coastline (QND95) shapefile I have.
>>> (I also tried EPSG:27039)
>>> 
>>> 
>>> As you can see, projection-sleuthing is not one of my strengths.
>>> Can anyone point me in a direction to try and solve this?
>>> 
>>> Thanks in advance.
>>> 
>>> Kind regards,
>>> Zoltan
>>> 
>>> 
>>> -- 
>>> 
>>> =============================================
>>> Zoltan Szecsei GPrGISc 0031
>>> Geograph (Pty) Ltd.
>>> GIS and Photogrammetric Services
>>> 
>>> P.O. Box 7, Muizenberg 7950, South Africa.
>>> 
>>> Mobile: +27-83-6004028
>>> Qatar:  +974 5083 2722     www.geograph.co.za <http://www.geograph.co.za/>
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>> 
>> =============================================
>> Zoltan Szecsei GPrGISc 0031
>> Geograph (Pty) Ltd.
>> GIS and Photogrammetric Services
>> 
>> P.O. Box 7, Muizenberg 7950, South Africa.
>> 
>> Mobile: +27-83-6004028
>> Qatar:  +974 5083 2722     www.geograph.co.za <http://www.geograph.co.za/>
>> =============================================
>> _______________________________________________
>> Africa mailing list
>> Africa at lists.osgeo.org <mailto:Africa at lists.osgeo.org>
>> You can UNSUBSCRIBE at https://lists.osgeo.org/mailman/listinfo/africa <https://lists.osgeo.org/mailman/listinfo/africa>
>> 
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>> You can UNSUBSCRIBE at https://lists.osgeo.org/mailman/listinfo/africa <https://lists.osgeo.org/mailman/listinfo/africa>-- 
> 
> =============================================
> Zoltan Szecsei GPrGISc 0031
> Geograph (Pty) Ltd.
> GIS and Photogrammetric Services
> 
> P.O. Box 7, Muizenberg 7950, South Africa.
> 
> Mobile: +27-83-6004028
> Qatar:  +974 5083 2722     www.geograph.co.za <http://www.geograph.co.za/>
> =============================================
> _______________________________________________
> Africa mailing list
> Africa at lists.osgeo.org
> You can UNSUBSCRIBE at https://lists.osgeo.org/mailman/listinfo/africa

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Tim Sutton

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