Display DOQ at max resolution

[Sean Kelly]

Hi all,

I'm working on a setup where the initial display is a WMS layer. (DOQ from
TerraServer.)

With the help of Google and the online examples I have been able to hack
together a setup with php and mapscript where I can display a DOQ from
TerraServer as a raster layer.  The image is centered on a given lat/long.
Panning and zooming (out) will be allowed from this starting point. (map
projection is in latlong and map units are in decimal degrees).

My problem is I don't seem to be able to calculate extents from my center
point that allow me to get all the way in to the 1 meter per pixel
resolution that should be available in the TerraServer image.  I can get
close, bu I seem to either fall a little short of the desired resolution
or end up too far in and beyond the scale at which MapServer can render
the image.  I currently have minscale in the WMS layer set to a very low
level so it will not interfere with my testing.

I guess my questions are:

I'm computing my extents using estimations of lat/long offsets from center
that will get me "in the ball park" for the resolution I want. Have I
missed some facility in mapscript that will calculate extents based upon a
desired center point and scale?

How might I properly calculate the extents based upon a center point such
that I can take advantage of the maximum resolution available from the DOQ
in the raster layer without exceeding the display limits?

Thanks for any help in advance.

Sean