RE: [Autopilot] GPS based attitude

[Kahn, A. -A. <Aar...@it...>]

Hello,
  The solution comes from the fact that to get the winds they are asking the
pilot to fly a zig-zag course at a constant indicated airspeed.  By doing
this the computer can get the difference in the ground speed and track in
the different directions.  In this way one can "observe" the wind from
different angles, and thus compute direction and magnitutde.
  To get true airspeed the computer asks for temperature.  If you know what
the winds, the ground speed, and temperature, you can calculate the IAS and
the TAS analytically.  
  To get the heading, if you assume that you are in an airplane, and you
have the ground track, speed, and the wind information, you can compute the
true north heading.  If you then have position on the earth, you can compute
the magnetic variation of where you are, and thus the magnetic heading.

I hope that this answers your questions.

Take Care,
Aaron Kahn

-----Original Message-----
From: Curtis L. Olson
To: aut...@li...
Sent: 3/27/2002 11:25 PM
Subject: Re: [Autopilot] GPS based attitude

How do they get TAS and IAS off a GPS?  Windspeed and direction,
headwind, crosswind components?  I know there are gps's that include
an electronic magnetic compass and a air pressure based altimeter
[eg. garmin etrex vista], but I've not seen one with a pitot tube.

Curt.

Tramm Hudson writes:
> Aaron,
> 
> Here is a product that does something similar to your GPS based
> attitude / navigation project:
> 
> 	http://www.hangarb17.com/products.html
> 
> Assuming a stable aircraft, they produce an attitude estimate
> from altitude changes and rate-of-turn calculations produced from
> the GPS data.  It's not perfect and wouldn't work for a helicopter,
> but interesting none the less.
> 
> Trammell
> -- 
>   -----|----- hu...@sw...                         H 240-476-1373
> *>=====[]L\   Tra...@ce...              W 240-453-3317
> '     -'-`-   http://www.swcp.com/~hudson/                    KC5RNF
> 
> 
> _______________________________________________
> http://autopilot.sourceforge.net/     Development mailing list
> https://lists.sourceforge.net/lists/listinfo/autopilot-devel

-- 
Curtis Olson   IVLab / HumanFIRST Program       FlightGear Project
Twin Cities    cu...@me...                  cu...@fl...
Minnesota      http://www.menet.umn.edu/~curt
http://www.flightgear.org

_______________________________________________
http://autopilot.sourceforge.net/     Development mailing list
https://lists.sourceforge.net/lists/listinfo/autopilot-devel

************************************ 
If this email is not intended for you, or you are not responsible for the
delivery of this message to the addressee, please note that this message may
contain ITT Privileged/Proprietary Information.  In such a case, you may not
copy or deliver this message to anyone.  You should destroy this message and
kindly notify the sender by reply email.  Information contained in this
message that does not relate to the business of ITT is neither endorsed by
nor attributable to ITT. 
************************************