[Xastir-dev] [Xastir] Open Street Map support (read this)

[Curt, WE7U]

On Thu, 10 Jun 2010, Jerry Dunmire wrote:

> I spent well into late last night (this morning) trying to find the
> right place to put in the transition from continuous scaling to levels
> but I'm not quite there. I know what needs to be done but I'm still
> learning the code and looking for a single place that covers all the
> transitions.

Basically you just need one image that is slightly (or more) larger
than the current Xastir viewport extents, then tell Xastir to use it
and Xastir will use only what fits in it's viewport.


> I would also like to propose, to be implemented at the same time as
> the scaling change, a user option to use either the OSM levels or the
> linear scaling. My reasoning is that scaling bit maps generally
> produces blocky and/or blurry images. My personal preference is to
> trade off better looking maps for less flexibility in setting the
> scale, but I understand that others will have a different preference
> and I think I can accommodate both.

We've had excellent luck so far in doing it the one way.  I suspect
the stuff you've seen elsewhere before just wasn't implemented
properly, or they tried to scale too much.  We don't do that.  I'd
vote no on the above proposal just 'cuz it would complicate multiple
places in the code for no net gain.  I'm just one vote though.


> I also want to get to the point where we can cache and use the OSM
> tiles rather than large bitmaps. A slippy map implementation would be
> great, but probably beyond my present skills. The use of tile caching
> should provide a faster interface and eliminate large downloads for
> small position changes.

If we could get to caching tiles we could fix the problems we have
with MS Terraserver as well, when the map view gets too wide.  They
feed us something other than what we requested in that case, and it
therefore gets georeferenced wrong by Xastir.  Requesting tiles in
that case would bypass that problem.  Tiles could help with other
internet map sources too I'm sure.


> I have to travel for a couple of days starting tomorrow afternoon. So
> my goal, assuming you are not adamant that I not do it, is to fix the
> transition error before I leave. Then I can get started on the linear
> scaling when I get back.
>
> Will that be OK?

I'm not adamant.  Just didn't want you to waste your time.  Sounds
like that's a moot point.  Have fun!

I'm headed out too, perhaps tonight.  Hopefully will leave a nice
track for the 500 miles I'll be driving.

-- 
Curt, WE7U.                         <http://www.eskimo.com/~archer>
    APRS:  Where it's at!                    <http://www.xastir.org>
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