Underwater Optical Positioning With Beacon Scaling in Low Visibility
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Solution Overview
Problem
Current underwater positioning systems face challenges in achieving accurate positioning and orientation of objects due to limitations in satellite positioning, drift issues with unaided Inertial Navigation systems, and inaccuracies in acoustic and photogrammetric methods, especially in turbid or low-visibility conditions.
Innovation Solution
An underwater positioning system utilizing an active light source, such as LEDs, in conjunction with an imaging device and Inertial Navigation System (INS), which provides high accuracy by determining the angle and position of light sources, and uses scaling elements like calibrated bars or depth sensors to establish a reference frame, even in low visibility conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acoustic positioning systems are used underwater, then positioning can be achieved, but accuracy degrades with increasing water depth and is affected by noise and multipath effects
Solution Approach 1:
The patent replaces acoustic positioning systems with an optical imaging system that uses a camera to capture images of light sources on beacons. This substitution eliminates the problems of acoustic noise and multipath effects, providing more reliable and accurate positioning data throughout the water column without degradation with depth.
Solution Approach 2:
The patent introduces passive optical beacons with light sources as intermediaries between the rover and the positioning system. These beacons are deployed on the seabed and serve as reference points that the rover's camera can observe, enabling indirect positioning measurement that avoids direct acoustic interactions with the environment.
2Measurement precision
If LBL arrays of transponders are deployed on the seabed, then acoustic positioning can be achieved, but the system becomes expensive and requires costly deployment and calibration
Solution Approach 1:
The patent uses simple, inexpensive passive beacons with light sources instead of complex acoustic transponders. These beacons can be easily deployed on the seabed and do not require expensive calibration procedures, significantly reducing both equipment costs and deployment complexity while maintaining positioning accuracy.
Solution Approach 2:
The patent extracts only the essential function of positioning reference points from the complex LBL system, removing the need for acoustic transponders and their associated complexity. The simplified beacons provide sufficient reference information for the optical imaging system to achieve accurate positioning without the overhead of full LBL arrays.
3Measurement precision
If photogrammetry is used for underwater surveying, then relative positions can be determined, but the method requires relatively good visibility and significant processing power
Solution Approach 1:
The patent uses passive light sources on beacons that are prepared in advance and deployed on the seabed. These pre-positioned light sources provide consistent visual reference points that can be observed by the rover's camera, enabling photogrammetric measurements to proceed even in reduced visibility conditions without requiring significant additional processing power.
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
The system achieves precise positioning and orientation with accuracies better than 0.05 degrees and 1 millimeter error per meter, reducing drift and improving reliability in turbid or low-visibility environments by using active light sources and multiple sensors for redundancy.
Implementation Method 1
Propagation of light underwater has, however, serious limitations compared to propagation in air or free space and only green to blue light can propagate a substantial distance
Implementation Method 2
an imaging device for observing the light source and for determining direction data representing a direction or change in direction of the light source with respect to the imaging device
Data Source
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AI summary
An underwater positioning system (501) provides position information for a rover that is moveable underwater in a reference frame. The system includes a light source (530), a beacon (504), and scaling element (512, 528). The light source is moveable together with the rover between different positions with respect to the reference frame. The beacon includes an underwater imaging device (510) and is deployable in the water at a fixed position with respect to the reference frame. The underwater imaging device observes the light source at the different positions and determines direction data representing a direction or change in direction of the light source with respect to the imaging device. The scaling element provides scaling data representative of a distance between the imaging device and the light source.