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.