Mike
– you have the right idea. This website also does the calc: http://www.csgnetwork.com/tasgpscalc.html
Or
you can just find the wind direction and fly into the wind and then turn 180 and
fly out of the wind and just average your groundspeeds. This is also
TAS. But it’s tricky finding the wind direction. You need to line up
your heading and your track to find it.
My
GRT in my Legacy was computing a TAS that is 5 knots too high for
instance. GRT lets you calibrate this so now its more
accurate!
Dave
T.
Legacy
RG
From: Lancair Mailing
List [mailto:lml@lancaironline.net] On Behalf Of Michael
Newman
Sent: Fri, 12-07-2007 19:14
To:
lml@lancaironline.net
Subject: [LML] Computing TAS from GPS
tracks
I've been doing some
homework on how to calibrate airspeed indications and get the TAS of a plane.
Given 3 GPS tracks taken at the same airspeed you can compute a complete
solution for the heading on each track and the TAS.
Folks might be
interested in my spreadsheet which contains real data from my plane at low
altitude. I will gather some more data over time.
You can find my
spreadsheet via my Soaring and Flying page at: http://www.dragonnorth.com/soaring.html scroll
down a bit there is discussion a link to a reference document and a link to the
spreadsheet itself.
My true airspeed as
computed from my airspeed indicator is about 14 knots faster that the measured
result.