Compensation of magnetic data for autonomous underwater vehicle mapping surveys

• US 10,132,956 B2
• Filed: 09/21/2015
• Issued: 11/20/2018
• Est. Priority Date: 10/01/2014
• Status: Active Grant

• Current Assignee: Ocean Floor Geophysics, Inc.
• Original Assignee: Ocean Floor Geophysics, Inc.
• Inventors: Kowalczyk, Peter
• Primary Examiner(s): Tran, Khoi H
• Assistant Examiner(s): Peche, Jorge O
• Application Number:
  US14/860,099
• Publication Number:
  US 20160097875A1
• Time in Patent Office: 1,156 Days
• CPC Class Codes: B63G 2008/004 autonomously operating
• CPC Class Codes: B63G 8/001 Underwater vessels adapted for special purposes, e.g. unmanned underwater vessels; Equipment specially adapted therefor, e.g. docking stations self-propelled or direction controlled diving chambers with mechanical link to a base B63C11/42
• CPC Class Codes: B63G 8/34 Camouflage for other vessels B63G13/02; in general F41H3/00
• CPC Class Codes: B63H 23/00 Transmitting power from propulsion power plant to propulsive elements adaptation of transmission to allow adjustment in direction of propellers B63H5/125; transmission between wind motors and propulsive elements B63H13/00; in outboard propulsion units B63H20/14; adaptation of transmission to allow adjustment of location of propellers B63H20/08
• CPC Class Codes: G01V 3/165 operating with magnetic or electric fields produced or modified by the object or by the detecting device with electromagnetic waves G01V3/17
• CPC Class Codes: G01V 3/38 Processing data, e.g. for analysis, for interpretation, for correction
• CPC Class Codes: G01V 3/40 specially adapted for measuring magnetic field characteristics of the earth
• CPC Class Codes: G05D 1/048 specially adapted for water vehicles

Abstract

Embodiments of the present invention are generally related to compensation of magnetic data, and, in particular, to a system and method for compensation of magnetic data as collected during autonomous underwater vehicle mapping surveys.

Claims

1. A method for magnetic data compensation comprising:

providing at least one magnetometer mounted on a subsea vehicle;

maneuvering the subsea vehicle at a first altitude above a seafloor and at a first heading;

receiving, by a microprocessor, a first set of raw magnetic data from the at least one magnetometer based on the maneuvering;

receiving, by the microprocessor, subsea vehicle state data and subsea vehicle performance data concurrently with the receiving of the first set of raw magnetic data; and

processing, by the microprocessor, the subsea vehicle state data, the subsea vehicle performance data, and the first set of raw magnetic data to produce magnetic compensation coefficients, wherein the produced magnetic compensation coefficients do not reference the Earth'"'"'s geodetic frame of reference.

2. The method of claim 1, wherein the produced magnetic compensation coefficients reference a frame of reference comprising the at least one magnetometer and the subsea vehicle.

3. The method of claim 1, wherein the processing is independent of an ambient magnetic field so that influence of the ambient magnetic field is not taken into account.

4. The method of claim 1, further comprising performing a subsea mapping and receiving a second set of raw magnetic data output from the at least one magnetometer while performing the subsea mapping.

5. The method of claim 4, further comprising applying the magnetic compensation coefficients to the second set of raw magnetic data to produce compensated magnetic survey data.

6. The method of claim 1, further comprising maneuvering the subsea vehicle at a second altitude above the seafloor at the first heading.

7. The method of claim 4, further comprising maneuvering the subsea vehicle at a second altitude above the seafloor, wherein the subsea mapping is performed at a survey altitude above the seafloor, the survey altitude between and including the first altitude and the second altitude.

8. The method of claim 1, further comprising maneuvering the subsea vehicle at a second altitude above the seafloor at a second heading.

9. The method of claim 1, further comprising maneuvering the subsea vehicle at the first altitude above the seafloor at a heading 180 degrees from the first heading.

10. The method of claim 1, wherein the maneuvering step comprises maneuvering the subsea vehicle in a rectangular loop.

11. The method of claim 1, wherein the subsea vehicle state data comprises a depth of the subsea vehicle form the sea surface and an altitude of the subsea vehicle above the seafloor.

12. The method of claim 1, wherein the subsea vehicle performance data comprises variable thruster motor currents.

13. The method of claim 1, wherein the subsea vehicle comprises one of an ROV and an AUV.

14. The method of claim 1, wherein the maneuvering the subsea vehicle at the first altitude and at the first heading is part of a series of maneuvers that moves the subsea vehicle in one of a clockwise direction and a counter-clockwise direction in a first loop that comprises a first plurality of legs.

15. A system to produce compensated magnetic underwater survey data comprising:

at least one magnetometer configured to mount to a subsea vehicle;

a non-transitory computer readable medium including instructions;

a processor in communication with the non-transitory computer readable medium, the processor operable to execute the instructions to;

receive a first set of raw magnetic data from the at least one magnetometer;

receive subsea vehicle state data and subsea vehicle performance data concurrently with the receiving of the first set of raw magnetic data;

processing the subsea vehicle state data, the subsea vehicle performance data, and the first set of raw magnetic data to produce magnetic compensation coefficients;

receiving a second set of raw magnetic data output from the at least one magnetometer while performing the subsea mapping;

applying the magnetic compensation coefficients to the second set of raw magnetic data to produce compensated magnetic survey data;

wherein the first set of raw magnetic data is collected while the subsea vehicle maneuvers at a first altitude above a seafloor and a first heading;

wherein the second set of raw magnetic data is collected while the subsea vehicle is performing the subsea mapping; and

wherein the produced compensated magnetic survey data does not reference the Earth'"'"'s geodetic frame of reference.

16. The system of claim 15, wherein the magnetic compensation coefficients reference a frame of reference comprising the at least one magnetometer and the subsea vehicle.

17. The system of claim 15, wherein the processing is independent of an ambient magnetic field so that influence of the ambient magnetic field is not taken into account.

18. The system of claim 15, wherein the subsea vehicle state data comprises a depth of the subsea vehicle from the sea surface and an altitude of the subsea vehicle above the seafloor.

19. The system of claim 15, wherein the subsea vehicle performance data comprises variable thruster motor currents.

20. A method for magnetic data compensation comprising:

providing at least one magnetometer mounted on a subsea vehicle;

maneuvering the subsea vehicle at a first altitude above a seafloor and at a first heading;

receiving, by a microprocessor, a first set of raw magnetic data from the at least one magnetometer based on the maneuvering;

receiving, by the microprocessor, subsea vehicle state data and subsea vehicle performance data concurrently with the receiving of the first set of raw magnetic data; and

processing, by the microprocessor, the subsea vehicle state data, the subsea vehicle performance data, and the first set of raw magnetic data to produce magnetic compensation coefficients, wherein the produced magnetic compensation coefficients do not reference the Earth'"'"'s geodetic frame of reference,

wherein the maneuvering the subsea vehicle at the first altitude and at the first heading is part of a series of maneuvers that moves the subsea vehicle in one of a clockwise direction and a counter-clockwise direction in a first loop that comprises a first plurality of legs, and

wherein, subsequent to the subsea vehicle completing first plurality of legs, the series of maneuvers moves the subsea vehicle in the other of the clockwise direction and the counter-clockwise direction in a second loop comprising a second plurality of legs.

21. The method of claim 20, wherein each leg in the first plurality of legs and the second plurality of legs includes a first portion of the leg where the subsea vehicle moves at the first altitude and a second portion of the leg where the subsea vehicle moves at a second altitude, different from the first altitude.

22. The method of claim 20, wherein the second loop is a reversal of the first loop that follows the same path as the first loop in reverse, and wherein the first and second loops are rectangular.