During the last six months, I have cooperated with the hot air balloon club Ballongveteranerna to create an electronic solution to measuring winds at low altitudes, called Windsond. The development is sponsored by the Swedish Airsport Federation.
Wind conditions are of paramount importance for hot air ballooning, where the balloon drifts with the wind. The only means of flight path control lies in choosing the altitude. Interestingly enough, the wind direction and speed can differ a great deal at different altitudes so precise control is possible for a skilled pilot.
Windsond consists of a GPS, battery, microcontroller and radio transmitter. By attaching a Windsond to the small pilot balloon, a computer with a radio receiver can track the ascent without human involvement and present graphs of wind speed, direction and temperature. Once the sond reaches an altitude of 1000 m, it detaches from the balloon and slowly falls to the ground where it beeps and blinks to assist recovery. So far, we have released three balloons with Windsond. The software can be further polished but system basicly works well. Good radio reception was demonstrated from 2 km altitude and 5 km ground distance.
In mid-August, we will travel to the World Hot Air Balloon Championship to use Windsond for the two Swedish teams. The championship will transpire in Battle Creek, Michigan, USA.
I will continue to improve Windsond to offer it as a commercial product for reusable, cheap and easy low-altitude weather measurement.
Also see the dedicated Windsond page.