nonsquare pixels (was: Questions about extents and projections)

[Brian Peschel]

Sean Gillies wrote:
>
> Brian,
>
> Unless you're going through the WMS dispatcher, msDrawMap will fudge 
> and adjust the spatial extents of your map in order to preserve a 1:1 
> pixel aspect ratio. Look for the calls to msAdjustExtent.
>
> Sean
>
Well, I am not using the WMS dispatcher, so I see in msPrepareImage() 
where the extents are changing for the 'fudge'.  I do want non-square 
pixels.  So, I guessed that if I call:
    msSetConfigOption(map, "MS_NONSQUARE", "YES");
before msDrawMap() I would get the exact extent I requested.  However, 
the extents are still changing, so I am missing another spot where the 
extents are changing.

My extent before calling msDrawMap is
  EXTENT -113.981498074503 50.7247102624229 -113.961752952407 
50.7319757375771
my extent after the call is:
  EXTENT -113.981498074503 50.7226042699327 -113.961752952407 
50.7340817300673

whether I make the call to msSetConfigOoption() or not (I am using 
msSaveMap() before and after the call to msDrawMap() to get the 
extents).  My image is 609x354 pixels (width x height).

My resulting images are also blank (just the background color from my 
map file).

I am also running mapserver 4.6.2.  I see that 4.8.0 is out.  Would 
upgrading help here?