Method for determining difference in distance

摘要

The invention consists of a method which comprises a plurality of steps for determining difference in distance from a reference point to at least two sensor modules 10, 20 that are located under water. The sensor modules 10, 20 comprise means for sending and receiving acoustic signals to each other and to a hydrophone 30 at the reference point. Connected to the hydrophone 30 is a calculating unit 40 that utilizes arrival time of the received signals from the sensor modules to determine difference in distance from the sensor modules (10, 20) to the reference point.

主权项

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 T1 it takes from when the first acoustic signal is sent from the first sensor module until the first sensor module receives the second acoustic signal sent from the second sensor module; sending an acoustic data signal, comprising the time value T1, from the first sensor module to the hydrophone either immediately, or following a set time delay after the first sensor module receives the second acoustic signal sent from the second sensor module; 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 T1 and optional set time delays.