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 NOAA > NESDIS > NGDC > MGGD & STP > Geomagnetism

High Definition Geomagnetic Model

Directional drillers use the Earth’s magnetic field as a natural reference frame to orient the drill bit. The azimuth of the bottom-hole assembly is inferred by comparing the magnetic field measured while drilling (MWD) with a geomagnetic reference field. Crustal magnetic anomalies constitute a significant source of error in directional drilling, if not accounted for in the geomagnetic reference field. To meet increasing demand for accurate geomagnetic referencing, the U.S. National Geophysical Data Center (NGDC) produces the High Definition Geomagnetic Model (HDGM) which accounts for long-wavelength crustal magnetic anomalies. HDGM significantly reduces geomagnetic referencing errors.

The HDGM model includes:

Main field
Secular variation
Crustal field to degree 720
Basic model for external field
Compatible with major well planning software

The HDGM model is:

Updated annually (current version is HDGM2014)
Available as an NGDC product at annual charge of $20,060.
Big Boat

Geomagnetic declination maps for two drill sites (red crosses) at the Caspian Sea. The standard approach (left) does not account for crustal anomalies and therefore is unrealistically smooth. The advanced approach (middle) shows the long-wavelength crustal distortion accounted for by the global HDGM model. The best solution (right) makes additional use of an aeromagnetic survey to fully account for local distortion of the geomagnetic field.

For further details and case studies see:

Email us at to purchase the model.

New Features with the HDGM2014 Release:

Simple error model integrated into software
Automatic value testing on Graphical User Interface

Maus, S., M. C. Nair, B. Poedjono, S. Okewunmi, J. D. Fairhead, U. Barckhausen, P. R. Milligan, J. Matzka,
High Definition Geomagnetic Models: A New Perspective for Improved Wellbore Positioning, IADC/SPE Drilling Conference and Exhibition, 6-8 March 2012, San Diego, California, USA, isbn: 978-1-61399-186-2, doi: 10.2118/151436-MS, March, 2012.
Available for download at:

Recording of the conference presentation available at:, search for keyword "151436"

License-holders for HDGM
AIM Directional Services
Baker Hughes
Cathedral Energy Services
Crescent Directional Drilling
Devon Energy
Downhole Drilling Services
Ensign Directional Services
Integrity Directional Services
Hunt Advanced Drilling Technologies
Leam Drilling Systems
Magnetic Variation Services LLC
Mostar Directional Technologies
Occidental Oil and Gas
Phoenix Technology Services
Pioneer Natural Resources
Scientific Drilling International
Wellbenders Directional Services LLC