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High Definition Geomagnetic Model Receives Update

Model now incorporates satellite data collected over nine-year span

Silhouette of an oil well operating against a skyline at dawn.
Courtesy of

On November 15, 2022, NCEI’s High Definition Geomagnetic Model (HDGM) received its annual update. Along with software adjustments and routine corrections made to accurately represent Earth’s magnetic field, nine years’ worth of data collected from the Swarm satellite mission were incorporated. With this overhaul, the HDGM will be accurate until December 31, 2023.

The purpose of the HDGM is to serve as a model of the Earth’s geomagnetic field. More than 90 percent of our planet’s magnetism is produced by the shifting of electrically charged molten metals within its outer core. Other factors include currents in the ionosphere (part of the Earth’s atmosphere that reflects radio waves), magnetic metals in and on the planet’s surface, and space weather events. Due to the transitory nature of these forces, the geomagnetic field is in a state of constant flux and is regularly strengthening and weakening.

The unpredictability of Earth’s magnetism can cause difficulties for any sector that involves directional drilling, such as the gas and oil industries. Directional drilling operations cannot make use of the Global Positioning System (GPS) since GPS signals do not penetrate the ground. Instead, Earth's natural magnetic and gravity fields are used to find the orientation of the drill-bit. Because drilling hardware is often situated deep underground where magnetic field variations are stronger at small spatial scales, wells may be bored hundreds of meters off of the intended mark. Hence, accurate knowledge of the local magnetic field is important for estimating the wellbore path.

Uses for the HDGM

The HDGM serves as a solution to the issues that geomagnetic variations can cause. It is an authoritative source for those seeking to drill safely, accurately, and cost-efficiently. Well planners utilize the program to compute magnetic reference values, and are also able to integrate the model directly into their directional drilling software. The HDGM allows for precise positioning so that wells can be bored near each other in resource-rich areas with less risk of intersecting. 

Annual updates set the HDGM apart from other magnetic models in terms of accuracy, including the widely used International Geomagnetic Reference Field (IGRF), which only provides averages based on data collected over a five-year period. The former includes not only this, but also calculations regarding more immediate changes to the geomagnetic field, small-scale variations of magnetism in the Earth’s crust collected from satellites and marine surveys, and an annually averaged disturbance field. Crustal data drawn from magnetic trackline and grid data is archived by NCEI, which serves as the world’s largest repository of such information.

New “Real Time” Data

The HDGM Real Time (RT) is an iteration of the base HDGM software that allows for access to pertinent data with greater immediacy. Developed through a collaboration between NOAA and the University of Colorado, the HDGM-RT is unique among all other magnetic models in its ability to provide a live forecast of the Earth’s magnetosphere. This is accomplished by the incorporation of data collected from a series of solar wind-observing satellites and land-based monitoring stations, as well as cutting-edge machine learning algorithms that predict likely changes in the geomagnetic field. 

In addition, the HDGM-RT is able to track daily changes in the ionosphere at mid and low latitudes. At the cost of the necessity of an internet connection, the HDGM-RT allows for more efficient drilling during adverse space weather conditions by enabling live course correction.