Patent ID: 9119383
Filing Date: 2015-09-01
Classification: A01K,G01S

Abstract:
1. A method for determining difference in distance from a reference point to at least two sensor modules all of which are located under water, wherein the sensor modules are in signal connection with each other in that they comprise means for sending and receiving acoustic signals, and wherein the reference point comprises a hydrophone for receiving acoustic signals from the sensor modules the method comprising: sending a first acoustic signal from the first sensor module to the second sensor module; sending a second acoustic signal from the second sensor module to the first sensor module and the hydrophone either immediately, or following a set time delay after the second sensor module receives the first acoustic signal sent from the first sensor module; measuring in the first sensor module a time value T sending an acoustic data signal, comprising the time value T measuring arrival times of received acoustic signals on the hydrophone at the reference point; and determining the difference in distance values from the reference point to each of the sensor modules by calculating this difference in a calculating unit connected to the hydrophone at the reference point based on measured arrival times of acoustic signals on the hydrophone and on the time value T