Global geomagnetic reference model / 2027
HDGM2027
High-resolution magnetic referencing for directional drilling.
HDGM2027 combines a degree-2160 global crustal-field model with a new location-dependent uncertainty model, bringing finer magnetic detail and more informative error estimates to established HDGM workflows.
What is new
A higher-resolution global magnetic reference.
HDGM2027 advances two linked capabilities: a degree-2160 crustal-field model that resolves finer global magnetic structure, and an uncertainty model informed by the coverage and quality of the magnetic surveys behind it. Together, they connect increased spatial detail with an assessment of where the global reference is supported by observations.
Global crustal field
Extending the resolution of global geomagnetic models.
HDGM2027 extends the global crustal-field model to ellipsoidal harmonic degree 2160, more than twice the maximum degree of HDGM2026. Its 10 arcmin spatial resolution corresponds to approximately 9 km half-wavelength at the equator. The new model represents finer crustal magnetic structure while retaining the established ISCWSA HRGM classification.
Harmonic degree ISCWSA model-class minima and HDGM releases
ISCWSA category thresholds are published in the geomagnetic reference-model definitions.
Model uncertainty
A new model for location-dependent uncertainty.
The uncertainty model uses the coverage and estimated errors of individual airborne and marine magnetic surveys, together with unresolved crustal structure, to estimate the crustal-field uncertainty at each location. This connects the finer resolution of HDGM2027 to the information available to support its use in the field.
The complete error model also includes main-field uncertainty and external-field terms that vary with location and geomagnetic activity. Estimates for total field, declination and inclination are provided for G0–G4 storm levels and all conditions in ISCWSA Revision 4 and 5 lookup tables.
Directional drilling
Using HDGM2027 on a well.
HDGM2027 supplies the geomagnetic reference values—total field, dip and declination—used in well planning, survey error models and magnetic-field quality checks. Its location-dependent uncertainty tables inform the applicable ISCWSA wellbore survey error model; storm-level selection, tool codes and anti-collision criteria remain with the operator.
HDGM2027 may be sufficient without additional local correction, depending on the operating area and survey requirements. Where magnetic survey data are available, IFR1 offers local crustal corrections at even higher spatial resolution. SWC provides corrections for time-varying magnetic disturbances. Monarch can help assess the appropriate reference based on local data, depth and the positioning-error budget.
Continue your HDGM workflow. HDGM2027 retains the established console format and DLL interface used by well-planning software. HDGM support is documented for Well Seeker, KellyDown, WellArchitect and Aspen Sysdrill; Monarch provides COMPASS installation guidance. Confirm your host-software version and uncertainty-term setup with Monarch.
Product details
Technical overview.
HDGM2027 retains the familiar HDGM delivery and integration approach. The product sheet provides technical specifications, uncertainty information and integration guidance.
Download technical product sheet PDF · 2 pages| Coverage | Global geomagnetic reference model |
|---|---|
| Crustal-field resolution | Degree 2160; 10 arcmin spatial resolution |
| Coefficient representation | Spherical harmonics to degree 2190 and maximum order 2160 (SH2190), representing the ellipsoidal-harmonic model (EH2160) without additional spatial resolution |
| Field outputs | Vector components, total field, declination and inclination |
| Uncertainty | Location- and activity-dependent estimates; ISCWSA Rev. 4 and Rev. 5 tables |
| Model period | Main field and secular variation: January 1, 1900 to December 31, 2027 |
| Interfaces | Windows application, Excel tool, coefficient files, DLL, console application and Web API |
Continuity and licensing
HDGM continues with Monarch.
HDGM2026 was the final HDGM model produced and distributed by NOAA/NESDIS. Monarch Magnetics now produces and licenses subsequent HDGM releases, building on the established HDGM software with new global modeling and uncertainty capabilities.
Monarch's co-founders, Arnaud Chulliat and Manoj Nair, have led HDGM development for more than a decade. HDGM2027 preserves the established coefficient-file format and familiar DLL and console workflows. Direct coefficient-file readers may need to accommodate the larger degree-2190 representation.
Former HDGM-RT users
HDGM2027 + SWC-Global
SWC-Global provides global time-varying magnetic-field corrections. Together with HDGM2027, it offers a continuity path for the disturbance-field component previously supplied through HDGM-RT.
View SWCHDGM2027 licensing
Integrate HDGM2027 into your surveying workflow.
Contact Monarch for licensing, software integration, uncertainty information or guidance on selecting the appropriate magnetic reference.