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

Anne Blankert anne.blankert at geodan.nl
Sun Sep 26 19:40:52 EDT 2010

Hello list,

Is this a bug or a feature?

According to the documentation, MapProxy requests more than 1 tile at a
time from the remote WMS server. This is defined in proxy.yaml.

The default configuration seems to be:

# request x*y tiles in one step
#     meta_size: [4, 4]
#     # add a buffer on all sides (in pixel) when requesting
#     # new images
#     meta_buffer: 80

So when you define the following for your layer in services.yaml:
# use a tile size of:
            tile_size: [256, 256]

This should result in sending wms request for images of
(4 x 256 + 2 x 80) x (4 x 256 + 2 x 80) = 1184 x 1184 pixels.

For some reason, I see that sometimes MapProxy sends requests for other
1184 x 2081 pixels
1184 x 2284 pixels
1184 x 4179 pixels
1184 x 2478 pixels

This happens especially when zooming out. Maybe something to do with the
nul meridian?

In my case, the wms server complains about images being too large if
dimensions go beyond 2048x2048. This results in a WMS exception, which
MapProxy does not cache (should not be). This results in slower
responses and extra traffic to the WMS server. To me, it seems this
behaviour should not happen?

Documentation remark:
At http://mapproxy.org/docs/latest/configuration.html#services-yaml
under "meta_size"
it says: "A meta_size of [4, 4] will request 64 tiles in one pass". If I
understand correctly, this should read:
"A meta_size of [4, 4] will request 16 tiles in one pass"



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