Patent ID: 6941196

Claim:
A modified three lobe search method of finding a vertical velocity of a vehicle, comprising: (a) transmitting at least three acoustic pulses from a vehicle submerged in water toward a bottom surface; (b) detecting a returned acoustic pulse due to each of the transmitted acoustic pulses on the vehicle, after the transmitted acoustic pulses are reflected toward the vehicle from the bottom surface; (c) generating a first cost function from a time that is related to said acoustic pulses; (d) obtaining an independently estimated vertical velocity of the vehicle; (e) performing Fletcher-Powell cardinal searches on the first cost function beginning with the independently estimated vertical velocity, to find a main lobe velocity at a minimum value of a lobe of the first cost; (f) adding a lobe spacing velocity increment to the main lobe velocity, to determine a first side lobe velocity; and (g) subtracting a lobe spacing velocity increment from the main lobe velocity, to determine a second side lobe velocity.