True, we don't care where the needle points - we need polar north, it's entirely dependent on longitude, and in our usual case, stere centred on south pole, a simple special case.
Cheers, Mike On Tue, 29 Jun 2021, 01:06 Andrew C Aitchison, <and...@aitchison.me.uk> wrote: > On Fri, 25 Jun 2021, Michael Sumner wrote: > > > Hello, we're using `gdaldem aspect` on polar grid products and we need to > > convert the grid-oriented directions to compass oriented ones, > > location-specific directions, where "compass north" is dependent on > > longitude. > > I am curious; in the terminology of the British Ordnance Survey maps, > you are converting from "Grid North" but are you trying > to convert to "True North" or to "Magnetic North" ? > > -- > Andrew C. Aitchison Kendal, UK > and...@aitchison.me.uk >
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