The position information is calculated by the GPS module from the signal of the GPS satellites which are located around the earth. The 3-dimensional position is sent down to the GK-90C groundstation where it will be corrected with the stationary GPS signal (differential GPS).

After correction in the groundstation, the position information of the radiosonde is almost as exact as it would be by means of a radar, therefore, the pressure sensor for defining the height of the radiosonde can be omitted for a cost-saving reasons.

Flights with the differential C/A-code DFM-90 GPS radiosonde have shown that the error or the vertical position (height) is less than 20 meters, the error of the horizontal position is lower than 10 meters.

DFM-90 for scientific purposes or research tasks

The DFM-90 radiosonde has additional channels for direct inputs from supplementary sensors with resistances, capacitances and frequencies. Matching-up to sensors with the different electric properties is possible and provided for. A three-bit output for multiplexing greaty facilitates the use of complex sensor systems where several parameters have to be measured simultaneously.

Thanks to these features, the DFM-90 radiosonde has been used and established an excellent reputation as a multi-channel radiosonde with high reliability and flexibility.