Magnetic Field AtlasExplore Earth's magnetic field with context.
The Magnetic Field Atlas is a public, interactive map of magnetic field strength, direction, and change. Search a place or postcode, compare dates, and inspect the South Atlantic Anomaly using open models and observations.
What does the map show?
The main map starts with total field intensity from IGRF-14 on 1 January 2025 at 0 km above the WGS84 ellipsoid. A change view compares values from the same model at two dates. Selected point values are calculated from model coefficients; coloured map cells have a separate display resolution.
Where is the South Atlantic Anomaly?
The atlas highlights a relatively weak-field region with an adjustable intensity contour. The default 26,000 nT line is a chosen map threshold, not a universal radiation boundary. The anomaly is especially relevant to spacecraft operations.
Can I compare my location?
Search a place or postcode, enter coordinates, or click the map. Postcodes are approximate reference points rather than precise boundaries. Results describe modelled conditions and trends, not local measurements at a home.
Does a weaker field mean an unhealthy place?
No residential health rating follows from field decline alone. The atlas does not rank postcodes as healthy or unhealthy. Read the USGS explanation of magnetic fields and human health for the scientific context.
Models, measurements, and sources
Model estimates, satellite and ground measurements, and historical reconstructions are labelled separately. Available layers include IGRF, CHAOS, WMM, and EMAG2. Each layer's catalogue entry explains its coverage, resolution, attribution, and limits. The map also includes volcanic geology as a separate optional layer.