[Mapserver-users] default extent

[Steve Lime]

Who wrote that documentation? It's wrong so it was probably me... ;-)
The extent given in the map file IS the default extent. So, if you
access the application and don't specifiy and extent (via a myriad of
means) then that value will be used. There is no magic way to create it
in absence of setting it. The default is something like -1,-1,-1,-1 and
the scale computation code checks for a degenerate extent and reports
the error you mention.

The code *should* (in absence of an extent) examine all layers and come
up with a minimum bounding box. You can add this as a feature request to
bugzilla but it's not a high priority... Interestingly the tool (i.e.
msLayerGetExtent() function) to get that value has already been written
and just needs to be hooked up in the CGI version and perhaps as a
method for MapScript (eg. $map->setDefaultExtent();).

Steve

Stephen Lime
Data & Applications Manager

Minnesota DNR
500 Lafayette Road
St. Paul, MN 55155
651-297-2937

>>> Jan Hartmann <jhart at frw.uva.nl> 03/21/03 10:04AM >>>
The MS3.7 MapFile doc says under the MAP heading:

-------------------------------------
EXTENT [minx] [miny] [maxx] [maxy]

     The spatial extent of the map to be created. Most often you will 
want to specify this, although mapserver will extrapolate one if none
is 
specified.
---------------------------------------

It would be nice if EXTENT had some sort of default, but I always get
an 
error-message when I don't specify it:

(msCalculateScale(): General error message. Invalid image extent).

What exactly does this mean?

Jan

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