Underwater Distance Difference Determination via Acoustic Time-of-Flight
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Accurate measurement of distance between underwater sensor modules and a reference point is challenging due to factors like line stretching, temperature variations, and sound wave propagation velocity changes, leading to inaccuracies in sound-based distance calculation methods.
Innovation Solution
The method involves sending acoustic signals between sensor modules and a hydrophone, measuring signal travel times, and adjusting sound velocity calculations based on temperature measurements along the sound path to determine precise differences in distance, using a calculating unit connected to the hydrophone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sound waves are used to measure distance under water, then distance measurement is enabled, but measurement precision deteriorates due to temperature variations affecting sound propagation velocity
Solution Approach 1:
A temperature sensor is introduced as an intermediary device to measure water temperature along the sound wave propagation path. The temperature data serves as a mediator to correct the sound propagation velocity, thereby eliminating the harmful effect of temperature variations on distance measurement precision.
Solution Approach 2:
The sound propagation velocity parameter is dynamically adjusted based on measured temperature values. By changing the velocity parameter according to actual temperature conditions, the system compensates for temperature-induced measurement errors and maintains high precision despite varying temperature conditions.
2Measurement precision
If a fixed sound velocity of 1500 m/s is used for calculations, then calculation simplicity is maintained, but measurement precision deteriorates due to inaccurate velocity values
Solution Approach 1:
The sound velocity value is changed from a fixed static parameter to a dynamic parameter that automatically adjusts based on measured temperature conditions. This dynamic adjustment maintains calculation simplicity while significantly improving measurement precision, as the system adapts the velocity value to current environmental conditions without requiring complex manual intervention.
3Measurement precision
If local temperature measurement at sensor module location is performed, then measurement simplicity is maintained, but measurement precision deteriorates due to temperature differences along the propagation path
Solution Approach 1:
The temperature measurement process is segmented into multiple discrete measurement points along the sound wave propagation path. Instead of measuring temperature at a single location, the system performs measurements at multiple segments along the propagation path, capturing temperature variations throughout the entire path and improving overall velocity calculation accuracy.
Solution Approach 2:
The temperature measurement approach transitions from a single-point measurement to a distributed measurement along the propagation path, adding the spatial dimension to temperature data collection. This dimensional expansion provides a more comprehensive picture of temperature conditions throughout the sound path, enabling more accurate velocity calculations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides greater accuracy in distance measurement, enabling precise positioning and adjustment of underwater equipment, such as trawls and seismic cables, by accounting for temperature variations and sound velocity changes.
Implementation Method 1
The principle of these devices is to emit a sound wave and measure the time it takes before the same sound wave is reflected
Implementation Method 2
sensor modules comprise means for sending and receiving acoustic signals
Implementation Method 3
the sound propagation velocity is dependent on a number of factors such as water temperature, salt content, pressure, etc.
Data Source
AI summary
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 utilises 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.