Seismic Streamer Shape Correction with Inertial Magnetic Compensation
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Solution Overview
Problem
Magnetic anomalies in the Earth's field cause errors in magnetic compass readings on seismic streamers, leading to inaccurate positioning of hydrophones and seismic signal correlation on marine charts, particularly near magnetic poles or in high latitudes.
Innovation Solution
A non-magnetic inertial reference direction device, such as a gyroscope, is used to correct magnetic compass readings by providing a reference direction independent of the Earth's magnetic field, allowing for accurate estimation of hydrophone locations using a towed 'fish' equipped with a reference magnetic compass and inertial sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic compasses are used to measure direction in seismic streamers, then the system can determine streamer shape and hydrophone locations, but magnetic anomalies in the Earth's field cause measurement errors that lead to inaccurate positioning
Solution Approach 1:
The patent introduces a non-magnetic inertial reference direction device (gyroscope) as an intermediary to provide a stable reference direction that is not affected by magnetic anomalies. This intermediary device measures the aiming direction of the vessel independently of the Earth's magnetic field, allowing the system to correct compass measurements by comparing them against the inertial reference, thereby eliminating the harmful effect of magnetic anomalies on positioning accuracy
Solution Approach 2:
The patent replaces the magnetic-based measurement system with an inertial mechanical system (gyroscope) that operates independently of magnetic fields. The inertial reference direction device provides a stable reference that is not subject to magnetic anomalies, and this mechanical/inertial system substitutes for the vulnerable magnetic compass system in providing accurate directional reference for hydrophone positioning
2Ease of operation
If magnetic compass readings are used without correction, then the system is simpler to operate, but positioning accuracy deteriorates near magnetic poles or in areas with magnetic anomalies
Solution Approach 1:
The system performs self-correction by automatically comparing magnetic compass readings with the inertial reference direction from the gyroscope and applying corrections to the compass measurements. This self-service mechanism maintains positioning accuracy without requiring manual intervention or complex external calibration procedures, thus preserving ease of operation while eliminating positioning errors in magnetic anomaly areas
Solution Approach 2:
The patent implements a feedback mechanism where the inertial reference direction device continuously provides reference measurements that are compared with magnetic compass readings. The system uses this feedback to automatically correct compass measurements and compensate for magnetic anomalies, maintaining high positioning accuracy without requiring manual calibration or complex operational procedures from the user
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
Corrects magnetic compass measurements to align with marine chart north, enabling precise hydrophone positioning and accurate seismic signal correlation, reducing errors caused by magnetic anomalies.
Implementation Method 1
an inertial reference direction device configured to measure a first deviation of an aiming direction of the instrument assembly vessel from a set reference direction
Implementation Method 2
a reference magnetic compass configured to measure a second deviation of an aiming direction of the instrument assembly vessel from a direction of an ambient magnetic field
Implementation Method 3
A non-magnetic inertial reference direction device, such as a gyroscope, is used to correct magnetic compass readings by providing a reference direction independent of the Earth's magnetic field
Data Source
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AI summary
An apparatus for correcting for deviation of an ambient magnetic field direction from a reference direction in a marine environment includes: an instrument assembly vessel configured to move through the marine environment; an inertial reference direction device disposed on the instrument assembly vessel and configured to measure a deviation of an aiming direction of the instrument assembly vessel from the reference direction; a reference magnetic compass disposed on the instrument assembly vessel and configured to measure a direction of the ambient magnetic field direction with respect to the aiming direction of the instrument assembly vessel and to transmit the measured direction; and a processor configured to receive the measured deviation and the measured direction and to calculate the deviation of the ambient magnetic field direction from the reference direction using the received measured deviation and direction.