[Proj] map coordinates in different coordinate system

Frank Warmerdam warmerdam at pobox.com
Wed Jul 8 10:28:15 EST 2009

stretch wrote:
> -------------------------------- 
> I am referencing the proj4js combined and compressed js file, and I am
> referencing the two additional EPSG2054.js and EPSG4148.js, which contain: 
> Proj4js.defs["EPSG:2054"] = "+proj=tmerc +south +ellips=WGS84 +datum=WGS84
> +lon_o=31 +k_0=1 +units=m +no_defs"; 
> and 
> The coordinates are changed, but not correctly - i.e they are converted from
> metres to metres, where they should be displaying dd. 
> The first thing you will notice is that 2054 is not a standard. Would
> someone be able to verify the correctness of this format?.
> I have successfully translated coordinates previously using just
> "+proj=tmerc +ellips=WGS84 +datum=WGS84 +lon_o=31"


I think the proj4js project uses the MetaCRS mailing list for discussions.
However, I suspect Mike Adair is also on this list.  I'm not to familiar
with the details of proj4js's implementation so I'll speak briefly from
the PROJ.4 point of view.

I am not sure why you say that EPSG:2054 is not a standard. It is a normal
part of the EPSG database. However, it uses the projection method
Transverse Mercator South Orientated.  The normal software used to translate
the EPSG database to a PROJ.4 dictionary does not handle this projection
method since I'm uncertain if it is plain transverse mercator, or if there
is also an implicit change in direction of the Y values (to southings
instead of northings).

I believe that for PROJ.4 the +south parameter is only used with UTM,
not transverse mercator.  So it is likely not being used in this

I also suspect that +lon_o should be +lon_0 (note use of a zero instead
of a lower case letter "O").

I'm not sure if any of this will help you though.

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

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