[aprssig] APRS Symbols- Direction/Vectoring

Steve Dimse k4hg at tapr.org
Tue Dec 7 12:31:41 EST 2004

On 12/7/04 at 8:22 AM Curt, WE7U <archer at eskimo.com> sent:

>Xastir has four rotations for each symbol.  We do flip pixels.
The problems I see with this are first, it only gives you 4 compass points,
second, it gives no indication of speed...so one of the 4 projections must be
used as well when a station is not moving, and finally, some icons are symmetric
about the vertical axis, for example the balloon, so these can only show two
values (east/west/stationary) and (north/south).

I much prefer the way MacAPRS has done it for the last 10 years, a vector drawn
from the icon in the direction of travel, the length of the vector giving an
indication of speed. Now that I think about this, I have to wonder why I never
implemented this in plot.cgi, it wasn't even on the to-do list. It is done now,
for example:


(At this time, this stations last report was 65 MPH, if you look at this and
don't see a vector, there must be a new report that has no speed, try a station
with motion to see the vector...)

I need to work on this a bit, the red vectors can get lost on maps using red for


Maybe I'll let the user specify a color. This is experimental, comments

Steve K4HG

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