The dropsonde is more rugged and heavier than the radiosonde since it must sustain a high wind speed at release. Because of its weight, the use of the dropsonde is limited to oceans where it is unlikely that it will do damage when it falls to the surface. A dropsonde equipped with a wind measuring device is a dropwindsonde. Omega signals are emitted from eight transmitters on the globe. These signals are used for precise positioning of ships and aircraft.
Loran signals are more accurate, but they are available only on coasts with much sea traffic.
Omega signals are precisely timed, so the locaion of a transmitter can be determined by the difference in time of signal arrival. This is archived by measuring the frequency shift of the base signals, much as Doppler radar provides the speed of various objects. A base station, which monitors the dropwindsonde, may be on board the aircraft that launched the sondde. A moving platform can be used since the timing of sognals at the sonde does not depend on the motion of the base station. These sensors include radiosonde sensors and lidar.