[Tilecache] tile index error for 2 layers in Open Layers

[Alain Bellenger]

Hello

I am using Open Layers and Tilecache to display two layers.
The layers have different extents and I think this is my main problem.

My layers in tilecache.cfg are defined as:

[plu]
type=WMSLayer
layers=plu
url=http://hostname/cgi-bin/mapserv.exe?map=plu.map
extension=png
resolutions=7.055551745557612,3.527775872778806,1.763887936389403,0.7055551745557613,0.35277758727788067
srs=EPSG:27582
bbox=791215.261,98199.634,795660.261,105144.629
size=256,256

[ortho]
type=WMSLayer
layers=ortho
url=http://hostname/cgi-bin/mapserv.exe?map=plu.map
extension=png
resolutions=7.055551745557612,3.527775872778806,1.763887936389403,0.7055551745557613,0.35277758727788067
srs=EPSG:27582
bbox=781000,66000,821000,106000
size=256,256


I am using the following javascript code to display my layers:

    var options = {
        format: 'image/png',
        projection: 'EPSG:27582',
        units: 'm',
        scales: [20000,10000,5000,2000,1000],
        maxExtent: new 
OpenLayers.Bounds(791215.261,98199.634,795660.261,105144.629),
        isBaseLayer: true,
        reproject: false,
        buffer: 1
    };
    var params=
    {
        layers: "plu"
     };

    // add layer 1
    glGlobal.layer = new OpenLayers.Layer.WMS( 'OpenLayers WMS',
        'cgi-bin/tilecache.cgi', params, options);
    glGlobal.map.addLayer(glGlobal.layer);

    var options2 = {
        format: 'image/png',
        projection: 'EPSG:27582',
        units: 'm',
        scales: [20000,10000,5000,2000,1000],
        maxExtent: new OpenLayers.Bounds(781000,66000,821000,106000),
        isBaseLayer: false,
        reproject: false,
        buffer: 1
    };
    var params2=
    {
        layers: "ortho"
     };

    // add layer2
    glGlobal.ortho = new OpenLayers.Layer.WMS( 'OpenLayers WMS',
        'cgi-bin/tilecache.cgi', params2, options2);
    glGlobal.map.addLayer(glGlobal.ortho);


    // zoom
    glGlobal.map.zoomToMaxExtent();


The previous code is what I want. When both layers are presents (one 
BaseLayer, the other not BaseLayer) there is an error with tilecache.
If I only have one layer as a BaseLayer and the other commented, there is no 
problem.

For example, if I have the layer "plu" as BaseLayer and "ortho" as not 
BaseLayer, tilecache says for a tile:

An error occurred: couldn't calculate tile index for layer ortho from 
([793382.72649599996, 102534.564992, 793563.34862099995, 
102715.18711699999])
  File "C:\DWebPro\deploy\www\cgi-bin\TileCache\Service.py", line 481, in 
cgiHandler
    format, image = service.dispatchRequest( params, path_info, req_method, 
host )
  File "C:\DWebPro\deploy\www\cgi-bin\TileCache\Service.py", line 397, in 
dispatchRequest
    tile = WMS(self).parse(params, path_info, host)
  File "C:\DWebPro\deploy\www\cgi-bin\TileCache\Service.py", line 122, in 
parse
    return self.getMap(param)
  File "C:\DWebPro\deploy\www\cgi-bin\TileCache\Service.py", line 129, in 
getMap
    raise Exception(


In OpenLayers, I see that the tiles for my layer "ortho" are aligned with 
the tiles of my layer "plu". And so tilecache complains. For tilecache, I 
suppose tiles for "ortho" are uniques and depend on the "ortho" bounding box 
and so if OpenLayers asks for an unknown tile, there is an error. Am I right 
?

If I am right, an answer to my problem should be having tiles for my layers 
which are not aligned. Does anybody know a mean to have this configuration ?

Thank you

Alain Bellenger

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