[Xastir] Open Street Map support (read this)

[James Ewen]

On Wed, Jun 9, 2010 at 3:05 PM, Jerry Dunmire <jerry at dunmire.org> wrote:

> The OSM code is really just a (simple) modification of the tigermaps
> code. The slow speed seems to be all related to pulling images from
> the server. It doesn't appear to me like the images in the cache get
> re-used if the center point changes. So even minor location changes
> can cause a new map to be pulled. A far better solution would be to
> cache OSM tiles (256x256), ala web based maps, but it I opted for the
> quick fix first...

It would be good to cache the map tiles on the local hard drive.

Lynn pulls the tiles, and caches them for use on the WinCE mobile
devices. I think he stores them for 7 days, or to a maximum amount of
space used. The user can over ride these values as desired. I have
caching set to never discard, as I want to use the large hard drive on
my laptop for offline use. I don't have a mobile data connection, so
it makes more sense for me to grab the tiles and keep them on my
drive. For limited resources like the Win Mobile devices, it's better
to dump old tiles, and download new ones as needed.

Speaking of this, when storing the tiles locally, one should keep in
mind the folder naming convention. I currently have my OSM tiles being
shared by RadioMobile, and APRSISCE/32. There's no need to have
multiple copies of the same tiles. If Xastir saves the tiles in the
same manner, then there's another shared resource available. Obviously
the programs being mentioned run on different platforms, but keeping
the same tree structure means that cross platform compatibility is
already in place if/when the programs merge or cross to the other
platform. I'm pretty sure that RadioMobile works under Wine, so the
need is probably already there.

Another thing that Lynn does that is interesting, is that he varies
the opacity of the OSM map in the background. I prefer my background
map to be as bold as possible, but Lynn likes his vary washed out.

Here are a couple screenshots that Lynn made of tracking a balloon
flight earlier today.

http://ldeffenb.dnsalias.net.nyud.net/Tracking/Balloons/WB9SKY-11-2010-06-09%20Burst2.png
http://ldeffenb.dnsalias.net.nyud.net/Tracking/Balloons/WB9SKY-11-2010-06-09%20Falling.png

You can see that the map in the background is very light. This makes
the user data POP right out at you. Looking at Tom's map of
Albequerque that he posted earlier brought this to mind. I had a hard
time seeing the APRS stations on the map, as everything was jumbled
together.

Perhaps varying the opacity of the map images is an idea that Xastir
can do as well. It is a handy feature.

James
VE6SRV