HIGH SPEED VELOCITY LOG

Abstract

ABSTRACTAdvanced high speed ships (surface effect ships, hydrofoils and air cushioned vehicles) under development will operate at speeds which are considerably higher than conventionally hulled ships. Precise velocity sensing and measuring techniques that provide the required accuracy throughout their operating speed range do not currently exist.This paper will discuss the Navy's development of a High Speed Velocity Log (HSVL), which will provide self contained, two‐axis velocity measurement for these advanced high speed hulls.The system selected by the Navy for an exploratory development program uses microwave doppler radar technology. The paper will discuss reasons why an FM‐CW doppler radar technique was chosen over other candidate technologies. The doppler radar technique involves the transmission of narrow beam radar signals down toward the water surface. Frequency of backscattered energy from the water surface is compared with the frequency of transmission to determine the “doppler” frequency shift from which ship's velocity relative to the water surface is computed.The paper will present test results of the HSVL feasibility model aboard the hydrofoil USS High Point (PCH‐1) and aboard the Amphibious Assault Landing Craft Jeff (B). In addition, a summary of an intensive analysis phase to determine HSVL critical design parameters will be described.