Magnetic Disturbance
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    17 years
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My wife and another woman were traveling by vehicle in northern Minnesota yesterday and I received a text from her stating:
"...Her GPS in truck goofs up on the (Iron) Range. The iron messing with it. Google fine tho..."
That reminded me when I took Ground School for Pilots (Private Ground School) fall of 1979, we had some discussion of the Magnetic Disturbance in northern Minnesota, which is also known as the Iron Range.
So, I checked the 2021-2022 Minnesota Aeronautical Chart on-line and there are several entries related to this:
"Magnetic disturbance of as much as 12° exists at ground level between Tower and Ely.
Magnetic disturbance of 8° exists at Grand Marais; other large disturbances exist at Pigeon Point, Pie Island, Welcome Island, Thunder Cape, Point Porphyny, Peninsula Harbor, and as great as 50° at Magnet and Pie Islands.
Magnetic disturbance of as much as 18° exists along the north shore at ground level and lake level from Duluth to Grand Marais."
So, what are the worst experiences you have had with Magnetic Disturbance adversely affecting your GPS receiver's performance?
During my wife's trip, the vehicle navigation system showed them at a different location, off-road, but her smartphone, likely using Google Maps, seemed to be relatively unaffected.
https://www.dot.state.mn.us/aero/aeronauticalchart/documents...
magnetic compass
A magnetic disturbance should affect a magnetic compass but it has no effect on a GPS.
Every marine chart has the magnetic deviation for that area posted. The chart has magnetic north and true north. When navigating by compass, magnetic north is used.
Solar Flares
What Dobs said above is true for GPSr's which use satellites to determine direction. Some units, mostly handhelds, also have a magnetic compass which is subject to surface as well as atmospheric abnormalities.
It is more likely the GPS disruption you mention is due to recent solar flare activity:
https://tech.hindustantimes.com/tech/news/beware-massive-sol...
http://support.optisurface.com/knowledgebase/articles/107773...
Starlink troubles
Many Starlink users reported unusual service interruptions this morning. Some have speculated that one way or another the solar flare activity was part or all of the issue.
On the other hand, while the Starlink User Terminal has an honest-to-goodness GPS receiver built in, I'm entirely sure it does not care a whit about either magnetic declination (the systematic positional error between magnetic north and true north, you can find a note for it on Geological Survey maps), nor magnetic deviation (local variation from the expected declination).
personal GPS user since 1992
GPS is unaffected by magnets and magnetic disturbances
My wife and another woman were traveling by vehicle in northern Minnesota yesterday and I received a text from her stating:
"...Her GPS in truck goofs up on the (Iron) Range. The iron messing with it. Google fine tho..."
Magnetic disturbances affect compasses, NOT GPS. GPS does not rely on magnetic fields and are immune to iron, magnets, etc. GPS relies on data signals and precise timing of those signals which are controlled by atomic clocks in the satellites and on the ground.
There have been a lot of military exercises recently that MAY affect GPS in your area. Some of these are well publicized in advance. Others can only be found in notices to airmen.
Good reason to stuff some
Good reason to stuff some legacy paper maps into the deepest recess of the car/truck. Probably never need to use them but they're there if gps goes kaput.
My only issue with a garmin gps was many years back (2009/10?). Back in the old nuvi days. I was somewhere between the IL/IN state line and indianapolis on some back road near i65. The gps shutdown and refused to boot back up. I putzed with it for a good 30 min before it came back. On subsequent trips, I took a spare gps with, loaded with the same map data and route files.
In the old days, one would tape a route sheet the their gas tank. Miss one turn and the whole route becomes useless.
Most magnetic anomily in my area
There is an area around Kingston Ontario Canada that has a Magnetic Anomily marked on nautical charts of 27° W to 3° E.
As noted above, this affects compass readings, not GPS signals.
Interruption of GPS signals may occur due to not having a clear view of the sky, travelling thru an area with poor GPS satelite coverage, or perhaps thru an area which creates a "Faraday box" effect (ie an iron bridge).
enclosures
or perhaps thru an area which creates a "Faraday box" effect (ie an iron bridge).
or a tunnel, or just a parking garage.
personal GPS user since 1992
Magnetic Disturbance
My wife and I traveled through that area yesterday. She was surprised that my Garmin Drive Smart seemed unaffected in the area!
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Good reason to stuff some legacy paper maps into the deepest recess of the car/truck. Probably never need to use them but they're there if gps goes kaput.
My only issue with a garmin gps was many years back (2009/10?). Back in the old nuvi days. I was somewhere between the IL/IN state line and indianapolis on some back road near i65. The gps shutdown and refused to boot back up. I putzed with it for a good 30 min before it came back. On subsequent trips, I took a spare gps with, loaded with the same map data and route files.
In the old days, one would tape a route sheet the their gas tank. Miss one turn and the whole route becomes useless.
And good idea to download maps onto your smartphone. Both Google Maps and Apple Maps can do this. Since your phone has built-in GPS receiver, it can match the GPS data to the map data to navigate -- even where there is no cellular service.