question on projections

[Frank Warmerdam]

Chris wrote:
> Hi everyone,
>
> I'm wondering how I can change from one projection to the other one the fly,
> depending on the area of the map I'm in.
>
> For example, if I'm using UTM projections, and I pan from one UTM zone to
> ther other, how can I switch my output projection let's say from UTM 16 to
> UTM 17.  It looks like I can only define one output projection in a map
> file.

Chris,

This would be tricky.  You would likely need to have a bunch of mapscript
magic to control something like this.  In "normal" use of MapServer, the
URL will have the requested region to display in the URL but the region is
in the coordinates of the map.  So you would have to do a whole bunch of
preprocessing magic in a mapscript script to recognise that a request has
wandered from one zone into another and transform the requested BBOX as
well as overriding the mapObj coordinate system.

I personally would encourage you to select a single coordinate system
appropriate for the whole region you want to work on if at all possible.
It would save you alot of headaches.

Best regards,
--
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | Geospatial Programmer for Rent