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> Grid north is the blue line on an OS map that points to the North Pole. > True north is the direction of lines of longitude that also converge at the North Po
by wcerfgba 4y ago
> Grid north is the blue line on an OS map that points to the North Pole.
> True north is the direction of lines of longitude that also converge at the North Pole, but this varies from grid north as it reflects the curve of the earth.
> Magnetic north marks the north-ward line to the magnetic North Pole.
If these are all 'lines' (or circles/rings on the Earth, or vectors) wouldn't it be more accurate to say that they've all converged to a single 'line', rather than a point? And wouldn't that mean there's a band around the Earth where they all point the same way? In that case, there must be loads of other points where these different norths have aligned, so what's so special about this particular village? Or am I fundamentally misunderstanding the geometry of this?
- rawling 4y agohttps://en.wikipedia.org/wiki/Ordnance_Survey_National_Grid#/media/File:Ordnance_Survey_National_Grid.svg https://en.wikipedia.org/wiki/Ordnance_Survey_National_Grid#... It looks like there's a line where grid north and true north always agree. https://en.wikipedia.org/wiki/North_magnetic_pole#/media/File:IGRF_2000_magnetic_declination.gif https://en.wikipedia.org/wiki/North_magnetic_pole#/media/Fil... Looking at this, it looks like "places where magnetic north matches grid north" might not be a straight line, or might not be a line that goes straight up and down the grid? E: maybe the former is the border between the red and blue areas here? https://en.wikipedia.org/wiki/World_Magnetic_Model#/media/File:Wmm2010declination.png https://en.wikipedia.org/wiki/World_Magnetic_Model#/media/Fi...
- wcerfgba 4y agoWow I had no idea that magnetic north was so wibbly!