Hi Ted,

SeeYou uses a filter, a sort of smoothing algorythm for the groundspeed
velocity calculations. Default value is 20s which means that 20 second.
You can control the smoothing through Tools Options Statistics
Groundspeed filter. Set it to "1s" to have "no filter".

Regards,
Andrej Kolar
--
glider pilots use
http://www.SeeYou.ws

On Thu, 2 Sep 2004 22:10:58 -0700, Ted Wagner
wrote:

A specific example:

In the log file in question, my take-off roll begins at 1:24:15pm, when
the
latitude/longitute fixes start to move.

Calculating the instantaneous speed as the distance from the previous
fix to
the current fix divided by the time between those two fixes, I have these
speeds:
+15 seconds: 43mph
+20 seconds: 59mph
+25 seconds: 72mph
+30 seconds: 81mph

But loading the same file in SeeYou and looking at the data that pops up
next to the mouse pointer and checking the speeds at the same points:
+15 seconds: 13mph
+20 seconds: 22mph
+25 seconds: 33mph
+30 seconds: 43mph

Those are some rather drastic speed differences. The tow plane was one of
Turf's Pawnees, which in the warmest weather don't have me sitting at 35
knots a full 30 seconds into the take-off roll.

The distance algorithm I'm using is the classic Great Circle:

distance_in_miles = 3956.0775034473 * arccos( SIN(lat1) * SIN(lat2) +
COS(lat1)*COS(lat2) * COS(lng1-lng2) )

Any other hackers out there played with this stuff?

-tw





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