OpenSeaMap-dev:Downloadable Raster Charts

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Status Quo

prefabricated charts

  • pros:
    • low stress on tile servers
  • cons:
    • set up needed
    • needs to be maintained
    • not always up to date
    • might not fit users needs


on demand

  • pros:
    • up to date
    • fits individual needs
  • cons:
    • high stress on tile servers
    • users have to do some research, might be a complex task



cache & proxy tile server

  • TileStache provides
    • numerous caches (eg. disk, Memcache, Amazon S3, MBTiles)
    • TMS and WMS proxy
    • fast and faster using nginx
    • cache max-age: 30 days?


  • served by cache & proxy tile server at minimum cost
    • tiles in TMS z/x/y directory structure (eg. gps-32, openlayers)
    • tiles in TMS z/x/y structure encapsulated in sqlite file ( mbtiles, eg. tilestache, OruxMaps, Locus)
    • single raster file stiched together via script and imagemagic (eg. .kap/openCPN)
    • gemf format - compact format for tiles, can be read by various libraries - e.g. osmdroid, simple to handle gemf format

bounding boxes/ tile sets

  • coastal / ocean / open waters
  • inland waterways
  • lakes
    • ...

web frontend

  • map showing boundingboxes according zoom level transas sample
  • sortable table
  • search by name/number/area/purpose
  • functions:
    • search prefabricated files, check age
    • trigger generating script in case file does not exist/ is obsolete