[MapProxy] Caches, Grids & Coverage help

Benjamin Wragg bwragg at isasolutions.com.au
Mon Jul 30 19:08:05 PDT 2012

Hi all,

I have a quick question about caches & grids and how they work with coverages. We have 3 areas we need to pre seed from one source tile server, but have different levels for each area. This will then be served out via a WMS layer with the seed_only:true setting. As an example, we would like the whole world at levels 0-2, one small country at 0-10 and another small country at 0-12. At first I set this up as 1 source, 1 cache and 1 grid. The grid was defined with num_levels: 13 (to accommodate the country with levels 0-12).  I then seeded the 3 different areas using coverages with the levels "to:" setting appropriate for each area.

The problem I'm having is when I access this via WMS, if I zoom in on a area other than the areas we pre seeded to levels 10 & 12, as I zoom in the image soon disappears and I get a blank screen rather than it keeping the world image of level 2 visible the entire time. I assume this is because of the num_level 13 setting? i.e its trying to load up a level of that area which isn't available as we only pre seeded that area with levels 0-2.

So to make this work what should I do? Do I :

1) create 3 grids, all identical just with a different num_level settings and have 1 cache which has a grid setting of:

grids: [my_grid_one, my_grid_two, my_grid_three]

2) create 3 caches each with their own grid and then have 1 layer with its source set to [cache_1, cache_2, cache_3]

3) something else?

Thanks for your help,



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