[Xastir] New code testing

[Curt Mills, WE7U]

On Wed, 23 Jul 2003, Bryce Wolfson wrote:

> Keep a running average count of how long it takes to draw the map (perhaps
> 5-10 draws' worth), then at the beginning of a map draw take the GPS input
> course and speed to project your position out the duration of a map draw,
> and draw the map centered there. If course/speed change during the draw you
> won't be at the center of the map by the time it's done drawing, but then
> you apparently aren't at the center by the time it's done drawing using the
> last-position-before-draw technique, either.

We'll call it dead-reckoning for maps.  hi hi

I'm curious why one should do the rolling average of 5-10 map draws.
I suppose that could be quite accurate if you're in a boat or plane,
doing roughly the same heading and speed for a while.  For ground
platforms I would think it counter-productive:  The course and speed
are constantly changing.

I'd vote for using only the time used for the last draw, or at the
most, the average of the last two draws.  Thoughts?

I'd further propose that once the predicted new location is found,
offset it on the screen so that you have 2/3'rds to 3/4's of the map
yet to move along before the edge is reached.  You'd see more of the
territory yet to travel, and less of the territory you've already
been over.  You also do map redraws less often that way, allowing
more processor time for GPS/Radio stuff.

Even cooler for mobile use would be track-up maps, rotating as you
go.  We're not even close to being able to do that yet, but it'd be
cool.  Actually, if you use a Garmin GPS and it's map screen, you
have that capability now with Xastir.  The GPS can do track-up mode,
you just ignore the laptop maps.  Someday I'll get a mapping GPS so
that this would actually be useful.  Right now I can see APRS
stations on the GPS map screen but I have few reference points
(maps) there, so have to resort to the laptop for that info.

-- 
Curt Mills, WE7U                    hacker_NO_SPAM_ at tc.fluke.com
Senior Methods Engineer/SysAdmin
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