Introduction

ION MagNav Workshop 2023, Monterey, CA

Aaron Nielsen and Rick Saltus

The views expressed in this article are those of the author and do not necessarily reflect the official policy or position of the United States Government, Department of Defense, United States Air Force or Air University.

Distribution A: Authorized for public release. Distribution is unlimited. Case No. 2023-0427.

Workshop introduction and agenda

• Introduction
• Background
• Magnetic maps
• Magnetic measurements and sensors
• Tutorial
• Lunch
• Compensation and calibration
• Navigation algorithms
• Wrap-up
  • discussion
• Social

Agenda

https://rpubs.com/friendly/test-newcommands https://quarto.org/docs/authoring/markdown-basics.html#equations

https://stackoverflow.com/questions/41362012/how-to-insert-font-awesome-icons-in-mathjax

Font-Awesome will only work for html type output

$$

$$

Background and Problem description

• Magnetic anomaly navigation (MagNav) overview

Magnetic Anomaly Navigation Overview

https://rpubs.com/friendly/test-newcommands https://quarto.org/docs/authoring/markdown-basics.html#equations

https://stackoverflow.com/questions/41362012/how-to-insert-font-awesome-icons-in-mathjax

Font-Awesome will only work for html type output

$$

$$

Refrigerator magnet

Earth’s core field (compass)

Crustal magnetic anomaly

1 000 000 nT

50 000 nT https://www.ncei.noaa.gov/products/world-magnetic-model (Chulliat 2020)

Range \(\pm\) 500 nT
Resolution \(\sim\) 1 nT https://mrdata.usgs.gov/magnetic/ (Bankey et al. 2002)

Requirements for MagNav

• Maps
• Sensors
• Platform Calibration
• Navigation Algorithms

Maps

Map-based navigation

• Features are required to navigate
• Magnetic anomaly closely tied to geology
  • less variation in coastal region
  • direction variation in Central Valley
  • more structure in Sierra Nevada mountains
• Area and direction of travel make a difference
  (Roberts and Jachens 2000)

Map coverage required - Earth Magnetic Anomaly Grid 2-arcsec v3

(Meyer, Chulliat, and Saltus 2017)

Sensors

Sensors

Vaquier towed magnetometer, National Museum of American History (Smithsonian Institution, n.d.) Ca. 1946

TwinLeaf uSAM

Platform calibration

An airplane is a big magnet that flies

\(|\vec{B}_\text{sensor}| = |\vec{B}_{\oplus}+ \vec{B}_\text{anomaly}+ \vec{B}_\class{fa fa-plane}{}|\)

Aircraft Calibration

Sensor placement and installation

• Engineered location
  • Stinger
• Survey for placement
• Non-magnetic fasteners

Degaussing

Algorithms

Sander Geophysics, Ltd

Navigation algorithms

Navigation algorithms

• Inertial navigation aiding

• Map-matching

  • Kalman filter
  • contour matching/Correlation processing

Inertial Navigation

• Inertial Measurement Unit (IMU)
  • measures accelerations \(\vec{f}\)
  • measures rotation rates \(\dot{\vec{\theta}}\)
• To get position from accleration, you have to integrate twice
  • continuously adds noise to your position estimate
• Drifting position estimate needs to be corrected
  • MagNav!

Map matching

• Sequential measurement Kalman filtering
• Contour matching/Correlation processing

References

Return

Main Page

Bankey, Viki, Alejandro Cuevas, David Daniels, Carol A. Finn, Israel Hernandez, Patricia Hill, Robert Kucks, et al. 2002. “Digital Data Grids for the Magnetic Anomaly Map of North America.” U.S. Department of the Interior, U.S. Geological Survey; Online; US Geological Survey. https://doi.org/10.3133/ofr02414.

Chulliat, A.;W. Brown;P. Alken;C. Beggan;M. Nair;G. Cox;A. Woods;S. Macmillan;B. Meyer;M. Paniccia; 2020. “The US/UK World Magnetic Model for 2020-2025 : Technical Report.” National Centers for Environmental Information (U.S.);British Geological Survey. https://doi.org/10.25923/ytk1-yx35.

Meyer, B., A. Chulliat, and R. Saltus. 2017. “Derivation and Error Analysis of the Earth Magnetic Anomaly Grid at 2 Arc Min Resolution Version 3 (EMAG2v3).” Geochemistry, Geophysics, Geosystems 18 (12): 4522–37. https://doi.org/10.1002/2017gc007280.

Roberts, Carter W., and Robert C. Jachens. 2000. “Preliminary Aeromagnetic Anomaly Map of California.” United States Geologic Survey. https://pubs.usgs.gov/of/1999/0440/.

Smithsonian Institution. n.d. “Developing Inertial Navigation.” On-line. https://timeandnavigation.si.edu/satellite-navigation/reliable-global-navigation/inertial-navigation/developing-inertial-navigation.