When Compasses Misbehave

[blessmycottonsocks]

There is a known magnetic field anomaly over part of the south Atlantic, which may overlap at least part of the traditional Bermuda Triangle.
Hope the link works - a bit fiddly copying a URL on my phone.

https://www.google.com/url?sa=t&sou...8QFnoECCkQAQ&usg=AOvVaw0EK1haFgNfhDPwcb8Js1dK

 

[charliebrown]

I can’t remember where but I saw an article displaying planet earth not as a smooth round ball but as a strange irregular shape planet with bulges.

I assume that these bulges have different magnetic field.

I can not understand why 1945 Flight 19 of the five Avengers got lost.

They just had to fly into the afternoon sun or west.

A real mystery.

 

[blessmycottonsocks]

The British Geological Survey produces a detailed, zoomable map showing magnetic anomalies over the British Isles, with red and orange showing the strongest local magnetic fields and deep blue the weakest. As you can see, London and the area due south is mostly red or orange. South Cornwall and Devon also figure highly on magnetic anomalies.
Click the URL below and select [View map] for the fully detailed version.

https://webapps.bgs.ac.uk/data/maps/maps.cfc?method=viewRecord&mapId=12033

 

[blessmycottonsocks]

Here's a zoomed section, with the location of The Devil's Punchbowl approximately where I've marked the blue X.
As you can see, it's in an area with a significant local magnetic field, so compass deviations shouldn't come as a surprise:

 

[DrPaulLee]

Flight 19 got lost because they confused the lands near Great Sale Cay, which was near their flight path, with the Florida Keys, which were well to the south and away from their route.

 

[kamalktk]

I can’t remember where but I saw an article displaying planet earth not as a smooth round ball but as a strange irregular shape planet with bulges.

It's as smooth as a competition valid billiard ball. https://www.discovermagazine.com/the-sciences/ten-things-you-dont-know-about-the-earth

There is some debate if it's quite that smooth, but it's quite smooth even if it's not.

The composition isn't even though, and sensitive enough devices detect that.

 

[blessmycottonsocks]

I get the occasional email from Outdooractive, suggesting hiking and cycling routes within a reasonable distance of my home location.
Tonight's email was "The Devil's Punchbowl, Old A3, cursed Murder Stone, Gibbet Hill and the Temple of the 4 winds".

That latter feature refers to a somewhat mysterious and now ruined hunters' lodge, which I have never visited before.
I definitely feel the urge to hike this route and will take my trusty compass along to check for anomalies.

https://www.outdooractive.com/en/ro...You-240517-0900&utm_campaign=#dmdtab=oax-tab3

 

[SimonBurchell]

I get the occasional email from Outdooractive, suggesting hiking and cycling routes within a reasonable distance of my home location.
Tonight's email was "The Devil's Punchbowl, Old A3, cursed Murder Stone, Gibbet Hill and the Temple of the 4 winds".

That latter feature refers to a somewhat mysterious and now ruined hunters' lodge, which I have never visited before.
I definitely feel the urge to hike this route and will take my trusty compass along to check for anomalies.

View attachment 76898

https://www.outdooractive.com/en/ro...You-240517-0900&utm_campaign=#dmdtab=oax-tab3

There's just a foundation left there now, but a nice area to walk. I'll see if I can dig out a photo.

 

[Mikefule]

Not sure if I've posted this elsewhere, but a person I have met several times, a friend of my mother and stepfather for decades, was involved.

He is a former policeman who lost a leg in a motorcycle accident. He used to do a lot of sailing, I think mainly coastal, in a small cabin yacht.

As a navigation exercise, he used to sail by compass and dead reckoning to a fixed position such as a large navigational buoy.

He was frustrated that his wife could usually get to within yards of the buoy on compass alone, and he often missed it by a couple of hundred yards.

Eventually, he worked out that it was the metal in his artificial leg affecting the compass which was next to the helm.


That aside, compasses do not "point north". They align with the local magnetic field. Mostly, that means aligning with the magnetic field of the Earth which results in the compass pointing approximately north. Sometimes, it means aligning with a stronger local magnetic field. Thus, it is not the compass that is "behaving strangely" but the magnetic field that is unexpectedly aligned.