[MapProxy] MapProxy asks for wms tiles that are too large

Oliver Tonnhofer olt at omniscale.de
Mon Sep 27 06:32:30 EDT 2010

On 27.09.2010, at 02:25, Anne Blankert wrote:
> I think I've figured out what might be happening:
> I am requesting tiles from MapProxy using the sphericalmercator
> projection (epsg:900913). My MapProxy is configured to request WGS84
> (epgs:4326) tiles from the WMS server. So what probably happens, is that
> the needed source pixel dimensions for WGS84 are much larger than the
> requested target dimensions for SphericalMercator. When zooming out, my
> client starts requesting tiles for more northerly regions and the more
> northerly you go, the bigger the horizontal pixel difference between
> WGS84 and SphericalMercator. If the source dimensions happen to go
> beyond the maximum dimension of the WMS server, a WMS server exception
> will occur.

Jepp, that assumption is right. MapProxy needs to enlarge the request size for transformed images.

> This means that when using reprojection, the requested WMS tiles may
> become unexpectedly large.
> So maybe users should set their meta_size to less than [4, 4]. According
> to the documentation this is a MapProxy global setting? Could/Should
> there be an override for meta_size at the layer level or an other
> solution to problem of some wms requests requesting image that are too
> large?

Not with 0.8.x, but with 0.9.x.


Oliver Tonnhofer <olt at omniscale.de>
Omniscale - Dominik Helle, Oliver Tonnhofer GbR
Nadorster Str. 60, 26123 Oldenburg
Tel: +49(0)441/9392774-2 (Fax: 9)

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