[Proj] map coordinates in different coordinate system

Gerald I. Evenden geraldi.evenden at gmail.com
Thu Jul 9 12:25:42 EST 2009

On Thursday 09 July 2009 12:22:30 pm OvV_HN wrote:
> Seems to me that EPSG:2054 is the Lon_0 = 31d Hartebeesthoek_1994
> Transverse Mercator projection.
> This has a south-west orientation.
> Haven't I read somewhere that you can put a minus sign in front of the k_0
> in (lib)proj to get the axes in south-west orientation?
> Oscar van Vlijmen

If just changing the sign of *both* the x and y (easting-northing) is all that 
is involved with the so call "south" orientation, then a negative k_0 will do 
the trick.  Standard proj4 does not make any check on [+]k_0 (aka k).

*However,* understand that k_0 multiplication is carried out on the basic 
projected Cartesian values before the false offsets are added.

As pointed out before, the [+]south option only applies to [+]proj=utm and 
causes the addition of  10,000,000 meters to the northing (y) value so that 
it is positive in the southern hemisphere.

The whole religious complexion of the modern world is due
to the absence from Jerusalem of a lunatic asylum.
-- Havelock Ellis (1859-1939) British psychologist

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