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RE: [aprsisce] Updating map tiles

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  • Fred Hillhouse
    +1 _____ From: aprsisce@yahoogroups.com [mailto:aprsisce@yahoogroups.com] On Behalf Of James Ewen Sent: Wednesday, April 25, 2012 08:56 To:
    Message 1 of 2 , Apr 25, 2012
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      From: aprsisce@yahoogroups.com [mailto:aprsisce@yahoogroups.com] On Behalf Of James Ewen
      Sent: Wednesday, April 25, 2012 08:56
      To: aprsisce@yahoogroups.com
      Subject: [aprsisce] Updating map tiles

       

      Lynn,

      Could you please add the ability to update the map tiles without
      having to delete them? With the new map license change, I have all
      kinds of tiles with missing roads and such, and it is a real pain to
      have to delete every tile that I have, and then spend hours going back
      and downloading all the tiles again.

      If I have the concept correct, if I have the purger disabled, map
      tiles will never get removed from my cache.

      The retain days sets the limit as to how long to hold onto the tiles.
      If the tiles are older than X days, and the purger is enabled, then
      the older tiles will get removed from the system.

      The concept was to try and use the /status to determine when a tile
      has been updated, but I believe that that doesn't actually do much to
      help us...

      What about this concept. If the tile is older than "retain days", and
      still in the cache, and we have an active internet connection, then go
      out and try and grab a fresh copy of the tile. The retain days becomes
      a trigger point for the program to use to check for fresher tiles. If
      the purger is enabled, the tiles still get removed from the system if
      they are older than "retain days", but if the purger is disabled, the
      tiles will stay in the tile directory. The way I see the program
      implementing this would be to check the age of the tile versus the
      "retain days" age when it goes looking for the tile in the tile
      directory, and if the tile is older, then go grab a new copy just as
      if the tile were no longer available.

      If you look at it in pseudo-code, what you have now is basically:

      Need tile x/y/z
      Does tile exist in directory?
      If no, go grab it from the internet.
      Display tile on screen.

      The change would be:

      Need tile x/y/z
      Does tile exist in directory?
      If no, go grab it from the internet.
      If yes, is tile older than "retain days"?
      If yes, go grab it from the internet.
      Display tile on screen.

      This minor change would allow the tiles to be refreshed after a
      specific number of days, yet still allow those who don't have 24/7
      internet access everywhere they go to retain the tiles for use when
      not tethered to the internet.

      Setting "retain days" to 0 and the purger off would mean that tiles
      are never checked for updates, and kept on the machine forever.

      If it were up to me, I would implement it such that there were a
      refresh time, and a retain time. The refresh time would work as
      described above, and the retain time would be a larger value that the
      purger would act upon.

      If I set refresh time to 7 days, and retain time to 90 days, tiles
      that are being used to draw the screen would get refreshed every 7
      days. Tiles that have not been needed to draw the map on screen and
      have not been used for over 90 days would get purged. Areas being
      actively viewed would keep updating the timestamp of the map tile and
      never age out to 90 days.

      I am loathe to scroll around the continent with APRSISCE/32 because as
      I look around, I am downloading map tiles that I may never look at
      again, yet there they sit in my tile directory because I have to have
      the purger disabled in order to have my desired map tiles available
      when away from an internet connection. The only way I can remove them
      with the program is to enable the tile purger, but that can delete
      tiles that I want to have available later. I can manually go into my
      tile directory, and figure out which subdirectories are in areas that
      I seldom frequent, and delete those directories, but that's a lot of
      manual work. I could also delete the whole tile directory, but that
      means downloading the whole map tile structure again.

      Just looking for a way to be able to eat all the cake that I have!

      --
      James
      VE6SRV

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