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The article explains that the WMM is "used widely in civilian navigation systems. For example, WMM is pre-installed in Android and iOS devices to correct for the magnetic declination.". However, it remains a mystery *why* these navigation systems, or Android devices, need this information. Those navigation systems typically use GPS, not magnetic fields. The only use for a compass I am familiar with together with GPS is to tell which direction you're facing when you start driving. But for that, even the crudest compass with no correction - and definitely not one that is updated every five years or less - is needed. So I'm still at a loss what the WMM is good for in civilian navigation, and I think the article should explain this better. Nyh (talk) 10:01, 6 February 2019 (UTC)Reply

https://geomag.bgs.ac.uk/education/smartphones.html Even if they don't do some ready reckoning to update the position when GPS is lost or inaccurate, smart phones adjust the measured compass bearing based on the model to determine true north. Flannelot (talk) 17:08, 9 February 2025 (UTC) Flannelot (talk) 17:07, 9 February 2025 (UTC)Reply

WMM accounts for when the GPS received signal is interrupted by interference, because the signal is weak and exists within the noise floor, causing the “lock” on center frequencies to drop—thus, losing real-time continuous data. AnyaArisohn (talk) 14:36, 6 February 2019 (UTC)Reply