[OSGeo Africa] Identify coordinate system
Zoltan Szecsei
zoltans at geograph.co.za
Sat Jul 13 07:19:32 PDT 2019
See my "Solved" email to the list....
My reality was that I did not ask what the vector data represented.
My strategy of looking for what projection had its origin on the equator
and some 500Km west of Doha correctly led me to UTM39N, but as I did not
realise that the data was cloud cover (there were no attributes in the
shapefile) I thought there was another error.
Thanks for the thought.
Regards,
Zoltan
On 2019/07/12 12:07, Abraham Parbhunath wrote:
>
> Hi Zoltan.
>
> Do you know approximately where the shape file is supposed to be
> relative to other datasets? Can you find common points between this
> unknown dataset and the others you have in that area? If there is
> common data, you could try a helmert transformation which should give
> you all the various parameters (e.g. scale swing rotation…..) and you
> could manually input these for your data and see where it plots. If it
> matches your data, then you could just manually define it using your
> known dataset. I assume there’s no metadata/xml file associated with
> the shapefile that can give a hint as to its origin also…?
>
> If not, then happy hunting J
>
> Regards
>
> Abraham Parbhunath
>
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> *From:*Africa <africa-bounces at lists.osgeo.org> *On Behalf Of *Zoltan
> Szecsei
> *Sent:* Friday, 12 July 2019 09:12
> *To:* africa at lists.osgeo.org
> *Subject:* Re: [OSGeo Africa] Identify coordinate system
>
> 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
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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 2722www.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 2722www.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
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