Christopher, Your email came in just as I posted a thought on my original posting. I said that "I wonder if the BUFFER is actually a buffer to both sides of the XY specified in "MAPXY"!
You've confirmed that I was nearly right! If it's a radius and the width of the image is greater than the height then the width in metres is indeed twice what is specified in BUFFER. Many thanks indeed. Regards, Donald -----Original Message----- From: Christopher Schmidt [mailto:[email protected]] Sent: 08 January 2009 19:24 To: Donald Kerr Cc: [email protected] Subject: Re: [mapserver-users] CGI mapserv.exe - BUFFER On Thu, Jan 08, 2009 at 05:47:09PM -0000, Donald Kerr wrote: > 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=500+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. "Buffer" is usually a 'radius' -- so, you've got 2000M on each side (4k total, instead of the 2k you expect). If you imagine picking the center piont, and drawing a $buffer_size circle around it -- that's your extent. Regards, -- Christopher Schmidt MetaCarta _______________________________________________ mapserver-users mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/mapserver-users
