World Magnetic Model 2025 released (and WMM2020 ending very soon!)

General
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If you’re using magnetometers and World Magnetic Model on your robots, pay attention!

The World Magnetic Model 2025 (with validity 2025-2030) has been released by NOAA a few days ago (they made it before DOGE starts biting :smiley: ).

What’s more important, WMM2020 validity ends on 31 Dec 2024. If you’re using the model and check for validity, it is time to update pretty fast! If you don’t check date validity, your model will probably still work fine, but the error would be larger and larger.

If you’re using GeographicLib, it hasn’t adopted the new model yet, but the data are already provided by a side-channel: How to apply WMM2025 model in GeographicLib? · Issue #34 · geographiclib/geographiclib · GitHub .

If you’re using magnetic_model ROS package, WMM2025 will be included in its next release.

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I’m pretty curious how many lawn-mowers will stop working in January :smiley:

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Oh whoa. This is like Y2K, but for AMRs. :grinning:

I know the earth’s magnetic field shifts over time and varies across the globe. I am curious, is there is a diff where I can see the net change in model accuracy?

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The model provides time derivatives, but those are only valid inside the validity time range.

For my place, declination is " 5.24° E ± 0.38° changing by 0.16° E per year ". So the accumulated error will probably not be that large. I’d expect extrapolation will make the error a bit larger.

You can compute declination yourself in this calculator: NCEI Geomagnetic Calculators .

And for viewing the historical development, there is a nice interactive map: Historical Declination Viewer . Unfortunately, it doesn’t show the change of the derivatives…