Patent ID: 8755250
Filing Date: 2014-06-17
Classification: G01S

Abstract:
1. A method of determining the velocity of an underwater object moving parallel to an underwater line array of a plurality of N equally spaced acoustic sensors that are part of an active sonar system comprising: making contact with the underwater object with a narrow band continuous wave pulse from the active sonar system at a frequency f determining the range R of the object from the line array with a shorter pulse from the active sonar system centered at a frequency f receiving a frequency f calculating the frequency shift (T plotting a line of frequency shift versus acoustic sensor for the measured Doppler shifts of a plurality of interior acoustic sensors to allow for confirmation of any difference in frequency using a linear least squares fit of the frequency shifts and to determine whether there is a measurable variation in the Doppler shift of the entire line array; calculating the variation in Doppler shift of the entire line array of N acoustic sensors, based on the frequency shift of the first acoustic sensor and the Nth acoustic sensor of the line array of N acoustic sensors, expressed as and determining the velocity of the underwater object according to the equation wherein c is the speed of sound in water and wherein Δθ is equal to the length of the line array of N acoustic sensors divided by the range R of the underwater object.