LADCP Inertial Navigation Correction for Ocean Current Precision
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current LADCP ocean current observation methods face challenges in achieving real-time, high-precision correction of current velocity and direction due to limitations in bottom tracking technology, leading to large measurement errors and inefficiencies in ocean current profile measurement.
Innovation Solution
An LADCP and combined inertial navigation system observation system that includes a lowered acoustic Doppler current profiler, a combined inertial navigation system host, data processing unit, wireless transmission module, and GNSS antennas, which performs real-time high-precision corrections using GNSS orientation data, roll angle, pitch angle, and course angular rate to improve measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If bottom tracking technology is used to obtain LADCP velocity relative to seabed, then ocean current velocity can be calculated, but measurement precision is poor except near bottom layer and three-dimensional movement velocity cannot be accurately calculated during lowering process
Solution Approach 1:
The patent combines LADCP with inertial navigation system (INS) and GNSS to create an integrated observation system. The INS provides continuous three-dimensional velocity data throughout the lowering process, while GNSS provides surface position reference. This merging resolves the limitation of bottom tracking technology by providing multiple independent measurement methods that work together across the entire water column.
Solution Approach 2:
The inertial navigation system acts as an intermediary between the LADCP and the seabed reference frame. Instead of directly tracking the seabed (which only works near the bottom), the INS measures the instrument's own motion through accelerometers and gyroscopes, providing velocity data at all depths without requiring seabed contact.
2Measurement precision
If LADCP is lowered to seabed to obtain to-bottom tracking data, then measurement coverage is improved, but working time is extended and working efficiency is reduced
Solution Approach 1:
The patent applies partial action by using inertial navigation data for the entire lowering process rather than requiring complete descent to the seabed for bottom tracking. The system can obtain sufficient measurement data without necessarily reaching the bottom, allowing earlier termination of the lowering operation and improved working efficiency.
3Ease of operation
If surveying ship is used as platform for LADCP measurement, then measurement capability is provided, but ferromagnetic object interference greatly impacts flow direction measurement of LADCP
Solution Approach 1:
The inertial navigation system's gyroscope acts as an intermediary for direction measurement, replacing the LADCP's magnetic compass. The gyroscope measures rotation and orientation without being affected by the surveying ship's ferromagnetic interference, providing accurate flow direction data despite the hostile magnetic environment.
4Measurement precision
If magnetic compass on LADCP is used to measure flow direction, then direction measurement is provided, but measurement precision is poor due to surveying ship's ferromagnetic interference
Solution Approach 1:
The patent replaces the magnetic compass (which relies on magnetic field interaction) with an inertial navigation system using gyroscopes and accelerometers. This mechanical/inertial system measures direction and motion through physical principles unrelated to magnetism, eliminating susceptibility to ferromagnetic interference from the surveying ship.
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 enhances the precision of flow velocity and direction measurements, reducing working costs and increasing efficiency in ocean current profile observation.
Implementation Method 1
LADCP (Lowered Acoustic Doppler Current Profiler, lowered acoustic Doppler current profiler) is a current profile measurement method that appeared in the 1990s
Implementation Method 2
The first GNSS antenna and the second GNSS antenna receive a GNSS satellite signal and transmit the GNSS satellite signal to the combined inertial navigation system host
Implementation Method 3
The combined inertial navigation system host observes a GNSS position, GNSS orientation data, three-axis acceleration data, a three-axis gyroscope angular velocity, a roll angle, a pitch angle, and a course angular rate
Data Source
AI summary
An LADCP and combined inertial navigation system combined observation system and method. The system includes an LADCP, combined inertial navigation system host, data processing unit, wireless transmission module, voltage-resistant wireless antenna, battery cabin, first and second GNSS antennae and an instrument support. The data processing unit is connected to the LADCP and the system host through serial ports to obtain ocean current profile measurement data, a GNSS position, GNSS orientation data, three-axis acceleration data, a three-axis gyroscope angular velocity, a roll angle, a pitch angle and a course angular rate. Real-time high-precision correction is performed on a three-dimensional flow velocity of an ocean current profile observed by the LADCP based on the orientation data, roll angle, pitch angle and the course angular rate. Accordingly, measurement precision of flow velocity and flow direction by the LADCP is improved, and working costs to carry out profile flow observation are reduced.