[Mapserver-dev] EPSG:NONE

Daniel Morissette morissette at dmsolutions.ca
Wed Nov 19 13:25:59 EST 2003

Ed McNierney wrote:
> Thanks for the reference!  The specification seems to say that the
> correct implementation is "SRS=NONE", not "SRS=EPSG:NONE", which makes
> perfect sense (the keyword NONE is not case-sensitive), and that this
> value *shall* be used for data whose spatial reference is undefined.
> The EPSG: prefix should be reserved for valid EPSG codes, and it sounds
> like (a) MapServer should support the SRS=NONE parameter and (b) PCI
> should fix their software to comply with the spec.

Perhaps MapServer should try to support SRS=NONE, but we need to think 
about the way to support this in a mapfile and internally.  For instance 
the spec also states that
  "Clients should not attempt to overlay information whose SRS=none
   with other information."
This restriction is important otherwise the behavior is undefined if you 
request a geographical layer using SRS=NONE or if you try to overlay two 
layers that don't have a SRS.

BTW, in WMS 1.2, SRS=NONE is replaced by 'CRS:1' which is the image 
(pixel) coordinate system.

I have created bug 485 about this:

  Daniel Morissette               morissette at dmsolutions.ca
  DM Solutions Group              http://www.dmsolutions.ca/

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