[mapserver-users] Strange coordinates used in GetFeatureInfo request

[Anzel, Phil - NRCS, Fort Collins, CO]

Hi, Daniel,

What a relief. Thank you so much for the clarification.

- Phil Anzel
       Contractor for USDA/NRCS
       ITC Web Soil Survey Team Member

Date: Sat, 23 Jun 2012 11:08:39 -0400
From: Daniel Morissette <dmorissette at mapgears.com>
To: mapserver-users at lists.osgeo.org
Subject: Re: [mapserver-users] Strange coordinates used in
        GetFeatureInfo request
Message-ID: <4FE5DBF7.9000504 at mapgears.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

On 12-06-23 11:00 AM, Daniel Morissette wrote:
> I didn't read your whole mail, but short answer is that I suspect you
> are overlooking the fact that in GetFeatureInfo, the X and Y coordinates
> are in pixels within the view of the map (which is 500x500 pixels in
> your example).
>
> So when you write x=0&y=0 that refers to the top-left corner of the map
> view, and not the 0,0 of the SRS coordinate system... which corresponds
> to longitude=-10, and latitude=+10. Actually, the x,y value is
> translated to be the center of the top-left pixel (and not its top-left
> boundary), which explains why you get lon,lat=9.98,9.98 in the query.
>


Please let me reword this last paragraph to make it a little more clear:

When you write X=0&Y=0 in your GetFeatureInfo request that refers to the
top-left corner of the map view which is located at longitude=-10, and
latitude=+10, and not to the 0.0,0.0 of the SRS=EPSG:4326 coordinate
system. Actually, the X,Y value is translated to be the center of the
top-left pixel (and not its top-left boundary), which explains why you
get lon,lat=-9.98,9.98 in the query.






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