[OpenLayers-Users] out of range bbox requests and Tilecache failures

[David Herbert]

Christopher,

I think maybe it comes down to how I choose to set up resolutions in
OL.  I originally used "auto", since I wanted the whole bounding box to
display at zoom level 0.  I think when that proved impossible when I
started to use Tilecache (auto isn't supported as an option there
obviously) I simply set maxResolution to be the first value in the
resolutions array I'd got from using "auto".  I understand from
Tilecache docs that I can specify:

levels (= numZoomLevels in OL)
resolutions (as per OL)
maxResolution (as per OL)

I have a fixed size of map div in which I want:

(1) The map to entirely fill the div at zoom level 0.
(2) 10 zoom levels.

Ideally I'd specify an array of 10 integer scales that I want (as
described under "preset zoom levels" in 

http://trac.openlayers.org/wiki/SettingZoomLevels 

but then I have to give Tilecache an array of resolutions (I don't
think it can take scales directly?), which I'd have to calculate from
units etc and map div size.  Introducing more FP rounding errors
perhaps? Also I'm not sure that would give me what I want in terms of
filling the div at zoom 0.  I'm certainly open to experimenting with
looking at differing ways of specifying the map zoom levels which might
be less error prone.  I'd appreciate your advice on how to go about
choosing resolutions/zoom levels given (a) the potential pitfalls of FP
arithmetic and (b) the need to operate with Tilecache too.

As for a page to demo this, it's unfortunately not possible right now
as my app isn't on a live server yet, nor is the Geoserver backend or
Tilecache.  

Thanks again for the help,

David.

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