NOAA > NCEI (formerly NGDC) > Geomagnetic Data & Info > HDGM Home

High Definition Data Coverage

Map of 28 km magnetic anomaly resolution availability (purple).

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Improved Resolution

Example of improvement in declination off the coast of Brazil by using the high resolution HDGM.

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The High Definition Geomagnetic Model (HDGM) is a global, high resolution model of the Earth's geomagnetic main and crustal field, providing magnetic field values (total field, dip, and declination) at any point above or below the Earth's surface. Well planners can use HDGM to compute magnetic reference values at any point, as well as easily integrate HDGM into their directional drilling software. HDGM is updated annually to correctly model secular changes in the geomagnetic field.


- Easy integration with most well planning software
- High resolution crustal field to degree 720 providing accurate down-hole declination and dip values
- Main field and secular variation models spanning years 1900-present
- Average external field model to estimate disturbance field
- Uncertainty estimates using ISCWSA error model
- GUI executable and Excel interface
- C-language library source code included for custom development needs