[Tilecache] TC called if OL maxextent bigger than a particular layer's ?

[Marco Nijdam]

Hi Yves,

Not too sure about the OpenLayers implementation, but I would expect
that the Layer's maxExtent could be different from the Map's maxExtent.
I see the there is even a property in Layer whether to request tiles
outside the Layer's maxExtent.

So why not set the Map's maxExtent to whatever you need, and keep the
Layer.TileCache maxExtent to what you already have?

Kind regards,
--
-- Marco Nijdam
--

As quoted from Yves Moisan:
> Hi All,
>
> We have a case where the maxExtent of our map needs to be larger than
> the area for which we have air photos (the layers we are tilecaching).
> Up to now, we have set both OL's maxExtent and tilecache.cfg's bbox
> element of the layers in question to the same value, which is to say we
> are deliberately restricting the map extent to the area covered by the
> tilecached layer.  However we need to use a larger mapExtent than that
> of the image layers, so the question is do we need to align the TC'ed
> layers bbox with the new maxExtent ?  According to the docs
> (http://tilecache.org/readme.html) there's no way around that.
>
> We would of course like to avoid doing that because the series of images
> we have is only a thin diagonal line in a huge bbox and we already have
> way too many blank tiles already so making the maxExtent larger would
> only generate more blank tiles.  Speaking of blank tiles, is there
> another way than to specify a bunch of bboxes to separate
> tilecache_seed.py calls to render only areas that have valuable info at
> very high zoom levels ?  The idea is that in the very unlikely event
> someone zooms in to level 10 in an area where ther is no image, the WMS
> server will be called to render blank images and that should not be too
> costly.  The most likely event of course is that people will zoom in
> where there are visible images and that would be taken care of by a
> series of bbox seeds.  How do people cope with OL.mapExtent > TC.bbox ?
>
> TIA,
>
> Yves
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