[mapserver-users] CGI mapserv.exe - BUFFER

[Fawcett, David]

Donald, 

I haven't played with BUFFER, but from the docs, my assumption is that
it builds a new extent by creating a buffer of the value BUFFER around
the point coordinate that you specify.  

So, if you buffer out 10000 meters from a point, you are going to get an
extent that is 20000 meters wide.  Think of the buffer value as a
radius, not a diameter.  

David.

-----Original Message-----
From: mapserver-users-bounces at lists.osgeo.org
[mailto:mapserver-users-bounces at lists.osgeo.org] On Behalf Of Donald
Kerr
Sent: Thursday, January 08, 2009 1:23 PM
To: 'Bob Basques'; mapserver-users at lists.osgeo.org
Subject: RE: [mapserver-users] CGI mapserv.exe - BUFFER


Bobb,

I don't quite follow you there to be honest. The BUFFER states that it's
"in the same coordinate system as the map file". How could that be
changed to image pixel values? What I'm try to do effectively is set the
width of the created image to a certain distance e.g. BUFFER=10000 which
(hopefully) will give me an image that's 10km across no matter what
pizel size I set in the querystring.

Regards,

Donald


-----Original Message-----
From: Bob Basques [mailto:Bob.Basques at ci.stpaul.mn.us] 
Sent: 08 January 2009 19:17
To: donald.kerr at dkerr.co.uk; mapserver-users at lists.osgeo.org
Subject: Re: [mapserver-users] CGI mapserv.exe - BUFFER


Donald,

I haven't tried this, but di you try using Image (pixel) values for the
buffer?

bobb



>>> "Donald Kerr" <donald.kerr at dkerr.co.uk> 01/08/09 11:47 AM >>>
I'd appreciate it if someone could give me some clarification please?

I am using the following url to return an image:

http://localhost/cgi-bin/mapserv.exe?map=/ms4w/os.map&mode=map&mapsize=5
00+4
00&mapxy=258544+665909&layers=all&buffer=2000

The documentation states, "BUFFER [distance] - A distance, in the same
coordinate system as the map file, used in conjunction with MAPXY to
create an new map extent".

The coordinate system is in metres so I would expect that the width of
the image (500px) would be 2000m (2km). That doesn't seem to be the case
i.e. the returned images is, at a guess, double that.

I need clarification on what "buffer" is actually doing. No doubt I'm
way off the mark with the deduction above!

Many thanks.

Regards,

Donald Kerr


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