[Tilecache] Problems with OpenLayers overview map

[David Herbert]

(Apologies for posting to both lists - not sure which one it belongs
in!).

I have Tilecache 1.9rc3 running as a CGI, and have had trouble getting
my OpenLayers overview map to display anything since.  If I look in
Firefox at pageinfo->media, I find that the tiles which should have
displayed my overview map are zero length, and if I type one such URL
e.g:

http://10.48.1.76:8084/?LAYERS=Coastline%20and%20bathymetry&STYLES=sggis_bathymetry_polygon%2Csggis_coastline&FORMAT=image%2Fpng&TRANSPARENT=off&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&EXCEPTIONS=application%2Fvnd.ogc.se_inimage&SRS=EPSG%3A2007056&BBOX=-1616%2C61560%2C-1104%2C62072&WIDTH=256&HEIGHT=256

into the browser, I get the following error:

An error occurred: can't find resolution index for 2.000000. Available
resolutions are: 
[200.37037000000001, 100.185185, 50.092592500000002,
25.046296250000001, 12.523148125000001, 6.2615740625000003,
3.1307870312500001, 1.5653935156250001, 0.78269675781250003,
0.39134837890625002, 0.19567418945312501, 0.097837094726562504,
0.048918547363281252, 0.024459273681640626, 0.012229636840820313,
0.0061148184204101565, 0.0030574092102050783, 0.0015287046051025391,
0.00076435230255126956, 0.00038217615127563478]

The overview map is given the following options:

var sgOverviewOpts = {
    'maxExtent' : new OpenLayers.Bounds(-82000,7800,80000,116000),     
 
    'maxResolution' : 200.370370,     
    'minResolution' : 0.5,
    'units' : 'm',
    'projection' : EPSG:2007056   
};

var overview = new OpenLayers.Control.OverviewMap(sgOverviewOpts);
map.addControl(overview);

which are the same as I give my Coastline/bathymetry base layer. My
tilecache.cfg contains the following for the same layer:

[Coastline and bathymetry]
type=WMSLayer
url=http://10.48.1.76:8080/geoserver/wms?transparent=off
layers=sggis:bathy_poly,sggis:coast_polygon
extension=png
bbox=-82000,7800,80000,116000
maxResolution=200.370370
srs=EPSG:2007056

Regular tiles for the map appear fine.  It's just when tiles are
fetched for the overview map that the problems arise.  Any idea how I
get round this?  

Thanks for any help,

David Herbert
British Antarctic Survey.

--  
This message (and any attachments) is for the recipient only.  NERC is subject
to the Freedom of Information Act 2000 and the contents of this email and any
reply you make may be disclosed by NERC unless it is exempt from release under
the Act.  Any material supplied to NERC may be stored in an electronic
records management system.