3D ultrasonic anemometer - plane airspeed = true wind speed?

Hello,
Is it possible dont predict wind speed but solve it.
For example by this:
3D ultrasonic anemometer(mount on the plane) - plane airspeed = true wind speed?

Any suggestions are welcome.

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Replies to This Discussion

TAS (true airspeed) is the vector sum of groundspeed and wind. So wind = TAS - groundspeed. TAS is usually measured using a Pitot-static system and a computer to correct for barometric effects. I don't know anything about 3D ultrasonic anemometers, so I can't comment on those. Groundspeed of course comes from a GPS.
Hi Recmaster,

Here is a method to determine air speed and wind speed from GPS, gyro, and accelerometer information, without the need for a pitot tube or any other sort of airflow measurements. It is presently incorporated in software of the UAV DevBoard, and works as follows:

1. Whenever the plane changes orientation, an accurate estimate of air speed magnitude is made by taking the ratio of the magnitude of the change in 3D ground speed vector, divided by the magnitude of the change in fuselage axis of the IMU, as seen in the earth frame.

2. From the airspeed and ground speed vector, wind speed vector is computed. There is stream of estimates, whenever the plane changes orientation, which are filtered.

3. Once the wind vector is known, MatrixPilot computes a high bandwidth estimate of the ground speed vector using "dead reckoning", which fuses gyro, accelerometer, and GPS information.

4. A high bandwidth estimate of airspeed vector is computed from ground speed and wind speed.

Attached is the track from a typical flight in windy conditions. The large yellow arrows indicate the wind vector field. The airplane icons indicate the orientation of the plane.

Best regards,
Bill Premerlani

Indicated airspeed (IAS) is measured by a pitot tube,   TAS is IAS corrected for density altitude. Density altitude is pressure altitude corrected for temperature.
"3D ultrasonic anemometer" - I'd like to know where to get one of those that doesn't cost a fortune and would fit in a small UAV......  I know the wind farm guys use such things but they look to cost \$\$\$\$\$\$ and be about the size of a microwave oven.

Hi,

what is the difference betwen Air Speed and Wind Speed?

Thanks.

Airspeed is typically the speed the aircraft is moving relative to the air it is in. (The speed of air moving over the body of the aircraft.) Wind speed it the speed the air is moving relative to the ground. Therefore, the speed the aircraft is moving relative to the ground (grounspeed, what GPS measures) is the vector sum of airspeed and wind speed.

When you are flying a kite the air hitting you in the face is the wind, it has a speed, wind speed. Lets call it 10 knots. The kite is behind you sat in a 10 knot breeze.

If we have a model aircraft it needs forward speed to create lift and fly. Lets say thats 20 knots. It airspeed.

If we fly that aircraft into the wind it would be pushing against that wind and its groundspeed, the speed it is making over the ground would be

20(airspeed) -10(wind) = 10 knots groundspeed

Turn the plane around so its flying downwind, or towards our kite on the string, then its 20 + 10 = 30 knots groundspeed

Air moves in three dimensions thermals have areas of lift and descent hills create lift all sorts of things.

So the real trick is measuring 3D wind, much like Bill does in the excellent UAV DevBoard project.

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