layers:
  bing_aerial:
    title: bing_aerial
    sources: [c_bing_aerial]
caches:
  c_bing_aerial:
    grids: [webmercator]
    #potentially add more sources
    sources: [s_bing_aerial]
    meta_size: [1,1]
    cache:
      type: mbtiles
      filename: bing_aerial.mbtiles
sources:
  #add your sources here
  s_bing_aerial:
    type: tile
    url: http://tiles.virtualearth.net/tiles/a%(quadkey)s.png?g=587&mkt=en-US&n=z
    grid: osm_grid
    concurrent_requests: 0
    on_error:
       404:
          # response: '#ff0080'
          response: transparent
          cache: False