Development of Bias error Correcting Method for Ocean CurrentVelocity Measured by Using Electromagnetic Log with Dual‐axis Sensors

Abstract

The trajectory prediction of drifting matter is always important for rescue operations on the sea. The ocean current for the prediction is usually observed by ADCP equipped on vessels of Japan Coast Guard. Recently a newly built high‐speed vessel is equipped with an electromagnetic log with dual‐axis sensors (EM 2 log) taking the place of ADCP, not to spoil its navigational capability. So we were required the evaluation of the ocean current observed by using EM 2 log and the development of processing methods for it.As the results of sea trials, we found a conspicuous bias error included in measured ocean current velocity. The bias error includes misalignment error and scale error, which are also contained in the ocean current observed by ship board ADCP. Although the method to reduce bias error is basically the same with that for ADCP data, dataset for correction of bias error should be prepared for each vessel in various vessel‐speeds. This paper shows a solution method to determine the dataset, named ’Random Cruising Method’.