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Re: [Paparazzi-devel] Trajectory pivoting in flight plan and wind direct

From: Martin Mueller
Subject: Re: [Paparazzi-devel] Trajectory pivoting in flight plan and wind direction/speed
Date: Fri, 05 Nov 2010 22:14:29 +0100
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv: Gecko/20101027 Thunderbird/3.0.10

Hi Roman,

First one: My flight plan trajectories are defined and each of them include a 
lot of points. I am looking for the way to pivot the trajectories including all 
the points about one point, so that the first part of the trajectory is always 
directed against the wind flow direction. Of course the wind direction will be 
defined before each flight. So I need to change all trajectories as I described 
before. Have anybody used something like this? Have you any ideas how to do it?

have a look at nav_cube.c. It contains some trigonometric functions to turn predefined lines/points around a center point.

Second one: I need to define on some way the direction and speed of the wind in the 
altitudes my flights carried out. As I can see GCS show me some data about wind speed and 
direction. But I ask me how precise is it? And what methods will be used to calculate it? 
I had an idea to calculate the wind speed and wind direction using ground speed (GPS), 
truth airspeed (Airspeed sensor) and drift distance, so as it was done in the "stone 
times" by the pilots. Another idea is to use a balloon with an anemometer, but the 
models I could use together with a balloon are quite expensive. Any ideas for how to 
measure the wind speed and direction in different altitudes using paparazzi equipment? Or 
some alternative methods?

The wind estimation is done in the gcs laptop with See that OCAML file for some theory and links. It uses the ground speed and statistic methods assuming that the true airspeed of the aircraft remains fairly constant throughout the measurement. The comparison with a tethered ballon showed that it is pretty accurate

There is another approach in the MatrixPilot that might be interesting to try\.googlecode\.com&sa=N&cd=1&ct=rc

Would be great if you could implement the classic approach with the airspeed, groundspeed and maybe a magnetic sensor.


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