On estimating the quality of doppler sonar data

This paper describes efforts to determine the accuracy (bias) and precision of water velocity measurements obtained with the MPL Doppler Sonar System. Precision is well quantified by comparing velocity estimates from similar sonars pointed in parallel. It is found that 2-5 cm/sec rms precision is possible after averaging over only 15 returns ( seconds). The smaller velocity errors are associated with longer pulses, which have poorer range resolution. Bias in Doppler measurements has been investigated by intercomparison of Doppler and electromagnetic estimates of the vertical profile of horizontal velocity. For the relative velocities present during the intercomparison, which were less than 30 cm/sec, no bias was detectable. Further tests are necessary at higher, known, relative velocities to quantify bias errors.