[postgis-users] suitable projection in metric system ?

[Francis Markham]

Hi Ahmet,

My quick Googling hasn't come up with a widely used pre-defined projection
for Turkey that is non zonal (either UTM or Gauss-Kruger), at least not in
the EPSG database.  Apparently, MapInfo ships with a Turkish Lambert
projection in its
mapinfow.prj<http://testdrive.mapinfo.com/techsupp/miprod.nsf/8248bf2b72f6949585257125006b035a/215efdb0c93153be85256a410055416a?OpenDocument>file,
which is widely available on the web.  I took the parameters from that
projection and created an entry on
spatialreference.org<http://spatialreference.org/ref/sr-org/7006/>as
SR-ORG:7006.  This can be inserted into PostGIS as a new SRS as:

INSERT into spatial_ref_sys (srid, auth_name, auth_srid, proj4text,
srtext) values ( 97006, 'sr-org', 7006, '', 'PROJCS["Turkish Lambert
Conformal (K.Eren -
ED50)",GEOGCS["GCS_European_1950",DATUM["D_European_1950",SPHEROID["International_1924",6378388.0,297.0]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Lambert_Conformal_Conic"],PARAMETER["False_Easting",1003827.0],PARAMETER["False_Northing",-1183453.0],PARAMETER["Central_Meridian",36.0],PARAMETER["Standard_Parallel_1",37.5],PARAMETER["Standard_Parallel_2",40.5],PARAMETER["Scale_Factor",1.0],PARAMETER["Latitude_Of_Origin",25.0],UNIT["Meter",1.0]]');

This can then be used as SRS number 97006.

Note that this projection uses the ED50 datum.  If your coordinates are in
WGS84 (the standard for GPS) or some other datum, it might be convenient to
create a new SRS using the above parameters but based on another datum.

Furthermore, If you are happy to keep your data in geographic coordinates
(lat/lon) you may wish to investigate the Geography type as Emily
suggested.  Be aware, however, that this has some cost in terms of speed for
some operations, and not all operations defined in PostGIS for Geometry are
currently available for Geography types.

Good luck,

Francis Markham

2010/11/5 ahmet temiz <ahmettemiz88 at gmail.com>

> hello
>
> I was wondering if you could tell me which projection in metric system
> is  suitable for whole country (TURKEY) ?
> I thought to use UTM, but it has three different zones.
>
> If you answer me, I will appreciate
>
> regards
>
>
> --
> Ahmet Temiz
> Jeoloji Müh.
> Planlama ve Zarar Azaltma Dairesi Başkanlığı
> Bilgi ve CBS grubu
> Eskişehir Yolu 10. km.
> Lodumlu / Ankara
> Tel : 0 312 2872680 / 1535
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> postgis-users at postgis.refractions.net
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>
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