Degrees of variation (from North)

[nigelp]

I’d be interested as to whether a GPS such as Garmin suffers the same variation as a phone. Most phones use a magnetometer and are supposed to point magnetic North. I can set my iPhone to true North but I don’t know how or whether the geographical variations are built into the app. I don’t use the true north option.

I have a Garmin so I can try that. When I have used a map app or a GPS the bearing presented has been the same as the one from a map and compass. They are then using GPS information rather than just the compass.

 

[TLM]

SatNav gives you accurate time and varyingly accurate position in your chosen geoid. Everything else is derived from those.

A phone has a fluxgate compass that gives magnetic north.

Grid north is something that was decided when a geoid and the used projection were chosen. In Finland we have four grid norths depending on where you are (military uses one and for rescue service it apparently depends). We also have quite a few magnetic disturbances locally because of iron ores.

A map and street signs still go strong.

 

[Pattree]

This has been very interesting!
I no longer hike very far but if accurate navigation were to be important I have completely changed my practice. I shall advise my grandchildren accordingly:

I have switched the iPhone to True North. (I didn’t know that I could until this week) and I shall use the grat points to establish true north on the map. I currently only have 1:50,000 OS so I can fold the map quite small and still see between four and six points on any ten mile square.

Thanks guys - a great job, I’m very glad I asked.

 

[Suffolkrafter]

Fascinating thread. I've noticed my phone compass varies in accuracy, sometimes recoverable by calibrating, but not always. But for me the main value in a phone sat nav is in providing a location, and my phone has yet to provide me an inaccurate location. I tend not to use the phone so much for bearings.

 

[matarius777]

It doesn't stick, moves OK & works fine....
....but it is a little yellow & a bit like a "snow storm" if shaken because of the rust like debris.

I think I shall write a strongly worded letter to Silva, I expect better seeing as I've only used it for around 40 years.

I would do! I have one that my father bought around 1975, possible a few years earlier, that hasn’t gone discoloured or rusty. Mind you, it hasn’t really had much use, certainly not for the last 40/42 years. I actually just bought some OS Explorer maps last week to relearn how to navigate with a compass because I rediscovered his old Silva whilst clearing my late mothers house, also have my grandfather’s sighting compass from whenhe was in the Royal Artillery, WW1.