OpenSeaMap-dev:Downloadable Raster Charts

Discussion

• see Discussion

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

Links:

• OpenNauticalCharts (outdated)
• Chart-Bundler (work in progress)
• kap.grade.de (showcase)

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

Links:

• Chart-Designer (work in progress)
• OSM-Wiki
• smrender-online
• MOBAC (banned by most tile-servers due to unreasonable load)
• GMapCatcher

Ideas

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?

formats

• 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
  • stick to well known INT-charts
• inland waterways
  • generate corridor (x-tiles wide) along centerline of waterway GMapCatcher example
• 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  • trigger generating script in case file does not exist/ is obsolete