Abstract: The sea-to-air monitoring system consists of an offshore monitoring platform and a shore-based ocean weather station. The former measures, at minute-level interval, wind speed, wind direction, number of satellites and other meteorological information at set location at sea and compresses those data. The compressed data is transmitted to the shore station through a second generation Beidou communication terminal. A unit vector averaging algorithm improved with probability and statistics theory is introduced to solve the 0°～360° crossing issue and improve the accuracy of wind direction measurement at lower wind speed. Since the bandwidth of Beidou communication channel is limited, an increment rounding dictionary encoding is used. The data compression rate of 36.0% with an accuracy of 97.8% is achieved.