Ship docking distance data monitoring display - has two sonar units on dock and includes signal acceptability circuit

摘要

A display system for ship docking data has two distance measurement units placed a distance apart along the dock driving a measurement circuit unit producing signals corresp. to the distance and/or speeds of ship sections to the docking points. The system automatically eliminates errors caused by sonar echo signal loss due to excessive docking angle or ship displacement along the dock. An error detection device monitors the derived signals which are accepted if the acceptability criteria are met. If they suddenly fail the test a value based on previous valid signals is substituted.