Measurement of Speed Through Water
The relevant issue with monitoring and measuring ship performance is the measurement of speed through the water. In 2016 an ADCP was mounted on a US Navy ship for the purposes of a hull monitoring program. At the onset of the program a baseline trial was completed to both determine the clean hull performance of the ship and the performance of the ADCP on a surface ship. The trial included completing reciprocals using standard calculations and ’triangles’ using more advanced calculations to calculate speed through the water. The results from the ADCP, maneuvers, EMLog, and surface based HFRadar corrections are compared in this report and examined for agreement and repeatability. The ADCP performed successfully showing strong agreement and repeatability though strong concerns still exist for long term viability. The EMLog was found to have issues beyond calibration offsets. The surface based HFRadar appears to be a passable correction method that may be of more benefit for measurement of ship maneuvers. The new method for analyzing GPS/INS speed over the ground data presented in this report is shown to have good agreement with the ADCP with the added advantage over the classic calculation by generating an associated uncertainty with the speed.