Doppler log is a precise instrument, which is used to measure ship velocity and calculate its voyage on the theory of Doppler Effect of sound wave in water. It has been an important equipment of ship navigation system for many years. In this thesis, we researched on the signal processing in testing the velocity of Doppler log and its implementation.The main tasks of this thesis are:1. This thesis studied the measurement methods of frequency in signal processing used in testing Doppler log's velocity. Compa...