[MapProxy] Limit a cache to a polygon

[gdis at arcor.de]

Hi all,

I have a data source (WMS) that serves aerial images.
I have another WMS that serves pipeline and facility data.
I have defined a grid with the maximum extent of all my data (pipeline and facility).

My goal is to create a cache with aerial images along a specific pipeline (just for testing purposes). Therefore I created a polygon file with a WKT polygon (which is completely inside my grid).
To limit the cache to this area I set the [coverages]-section of the seed to my polygon and set seed_only to true so that the data should be limited to the polygon extent.

Unfortunately MapProxy (v1.5) always generates data for the whole grid (according to the documentation this is the default behaviour when no coverage is defined).

Can anyone give me a hint what I missed? I've also installed the required libraries for using polygons. There is also no error during seeding.

seeds:
  pipeline_aerial_images:
    caches: [pipeline_aerial_images_cache]
    grids: [my_grid]
    coverages: [my_polygon]
    levels: [0,1,2,3]
    refresh_before: 
      weeks: 52

coverages:
  my_polygon:
    datasource: pipelines.txt
    srs: 'EPSG:31466'

The polygon file looks like:
POLYGON ((2546475.09223 5727924.37180,2529119.00058 5708805.99611,<.....>,2546475.09223 5727924.37180))


Maybe there is a better approach to limit the data to a specific region? I also tried to limit the source with the coverages but with no luck :-(


Thank you very much,
HS