Mats Elfström a écrit :
> Hi Cathy!
>
> This has been asked before, and I do not think there is an easy way
to do this.
> I have a recent case and can compare the defining strings.
> A shapefile I have in a swedish common projection has the following
prj info (in one string, disregard e-mail wrapping):
> PROJCS["RT90
2",GEOGCS["RT90",DATUM["D_RT90",SPHEROID["Bessel_1841",6377397.155,299.1528128254262]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["false_easting",1500000.0],PARAMETER["false_northing",0.0],PARAMETER["central_meridian",15.8082777778],PARAMETER["scale_factor",1.0],PARAMETER["latitude_of_origin",0.0],UNIT["Meter",1.0]]
>
> This relates to the following string in the mapinfow.prj file:
> "Svenska rikssystemet RT 90 2,5 gon väst (standard)\p3021", 8, 112,
7, 15.8082777778, 0, 1, 1500000, 0
>
> I have created the shapefile using Universal Translator, whose
coordsys.db file defines the same projection:
> RT90-2.5V|RT90 (Rikets Triangulering 1990) 2,5 gon V; Meters (EPSG
#2400)|EUROPE|RT90||TM|METER
>
> So all you have to do is to figure out which parameters connect, and
what lies behind esoteric strings such as EPSG#2400, GEOGCS and so on,
Some are self-evident, others more obscure. Of course, this does not
strike me as very efficient since UT obvoiusly knows how to do this, so
my suggestion is to use UT to create a library of the common projections
you want to use.
[...]
The EPSG Geodetic Parameters are maintained and published by the OGP
Surveying and Positioning Committee, through its geodesy sub-committee.
A web reference is http://www.epsg.org/
These parameters for coordinate reference system and coordinate
transformation description are used by many GIS software, including
MapInfo, which documentation said that the EPSG référence number is
noted \p in MapInfow.prj
It is strange that the universal translator EPSG#2400 corresponds to
Mapinfow.prj \p3012 number... but I've seen some differences too in
french systems between MapInfo and Mapserver (some pojections seem
to be defined with 2 numbers in EPSG database and it is sometimes
difficult to choose the right one !
--
Michel Wurtz
MAP/SG/SM/SDSI/CERIT/DIG
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