[MetaCRS] Re: ordering parameters in WKT fomat

[Howard Butler]

I would think it not be a problem, as most SRS implementations are trees and nodes meaning that order might not mean so much, but I don't feel qualified to say.  I'm forwarding this message on to the MetaCRS list, which should have the expertise to make a pronouncement one way or another...

Howard


On Apr 20, 2010, at 5:33 AM, Jean-Marie Condom wrote:

> Hello
> 
> I send you this email to make a comment about the WKT format provided on the site http://spatialreference.org
> which is a very useful site that I appreciate a lot
> according to WKT specification that I found at the following address :
> http://geoapi.sourceforge.net/2.0/javadoc/org/opengis/referencing/doc-files/WKT.html
> it is said that a projection is defined by entities ordered in the following way :
> <projected cs> = PROJCS
> ["<name>", <geographic cs>, <projection>, {<parameter>,}* <linear unit> {,<twin axes>}{,<authority>}]
> 
> 
> in the WKT format that I downloaded for some projection I noticed that the AXIS and UNIT parameters are switched
> 
> as an example if i ask for eps:27572, I get the following WKT description
> 
> PROJCS["NTF (Paris) / Lambert zone II",
>     GEOGCS["NTF (Paris)",
>         DATUM["Nouvelle_Triangulation_Francaise_Paris",
>             SPHEROID["Clarke 1880 (IGN)",6378249.2,293.4660212936269,
>                 AUTHORITY["EPSG","7011"]],
>             TOWGS84[-168,-60,320,0,0,0,0],
>             AUTHORITY["EPSG","6807"]],
>         PRIMEM["Paris",2.33722917,
>             AUTHORITY["EPSG","8903"]],
>         UNIT["grad",0.01570796326794897,
>             AUTHORITY["EPSG","9105"]],
>         AUTHORITY["EPSG","4807"]],
> 
>     UNIT["metre",1,
>         AUTHORITY["EPSG","9001"]],
> 
>     PROJECTION["Lambert_Conformal_Conic_1SP"],
>     PARAMETER["latitude_of_origin",52],
>     PARAMETER["central_meridian",0],
>     PARAMETER["scale_factor",0.99987742],
>     PARAMETER["false_easting",600000],
>     PARAMETER["false_northing",2200000],
>     AUTHORITY["EPSG","27572"],
>     AXIS["X",EAST],
>     AXIS["Y",NORTH]]
> 
> 
> which should be described in the following way :
> PROJCS["NTF (Paris) / Lambert zone II",
>     GEOGCS["NTF (Paris)",
>         DATUM["Nouvelle_Triangulation_Francaise_Paris",
>             SPHEROID["Clarke 1880 (IGN)",6378249.2,293.4660212936269,
>                 AUTHORITY["EPSG","7011"]],
>             TOWGS84[-168,-60,320,0,0,0,0],
>             AUTHORITY["EPSG","6807"]],
>         PRIMEM["Paris",2.33722917,
>             AUTHORITY["EPSG","8903"]],
>         UNIT["grad",0.01570796326794897,
>             AUTHORITY["EPSG","9105"]],
>         AUTHORITY["EPSG","4807"]],
>     PROJECTION["Lambert_Conformal_Conic_1SP"],
>     PARAMETER["latitude_of_origin",52],
>     PARAMETER["central_meridian",0],
>     PARAMETER["scale_factor",0.99987742],
>     PARAMETER["false_easting",600000],
>     PARAMETER["false_northing",2200000],
> 
>     UNIT["metre",1,
>         AUTHORITY["EPSG","9001"]],
> 
>     AUTHORITY["EPSG","27572"],
>     AXIS["X",EAST],
>     AXIS["Y",NORTH]]
> 
> but if I change this order does it have an impact on the definition of the projection ?
> 
> I would like your opinion about this comment
> 
> thanks a lot in advance
> 
> Jean-Marie
> -- 
> Jean-Marie Condom
> Software Engineer
> Sté Météorage
> 2 Avenue Angot
> 64000 Pau
> France
> 
> tél : +33 5 59 90 02 41
> Fax : +33 5 59 80 77 31
> 
>