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**Arctic sea ice / Re: "Stupid" Questions :o**

« **on:**August 10, 2019, 12:23:40 AM »

Uniquorn, the formulae for orthographic projection are here:

https://en.wikipedia.org/wiki/Orthographic_projection_in_cartography

They are taken from a book for which the .pdf file is available online: https://ia802909.us.archive.org/34/items/Snyder1987MapProjectionsAWorkingManual/Snyder%201994%20Map_Projections_a_Working_Manual.pdf

They are actually simple though, and simplify still further when centred on the North Pole.

phi_0 = 90 degrees

lambda_0 = -45 degrees (example with 'Greenland down')

x = R cos(phi)sin(lambda+45)

y = -R cos(phi)cos(lambda+45)

R ~ size scale of your map. You will presumably have to calibrate it using known coordinates, e.g. Svalbard.

https://en.wikipedia.org/wiki/Orthographic_projection_in_cartography

They are taken from a book for which the .pdf file is available online: https://ia802909.us.archive.org/34/items/Snyder1987MapProjectionsAWorkingManual/Snyder%201994%20Map_Projections_a_Working_Manual.pdf

They are actually simple though, and simplify still further when centred on the North Pole.

phi_0 = 90 degrees

lambda_0 = -45 degrees (example with 'Greenland down')

x = R cos(phi)sin(lambda+45)

y = -R cos(phi)cos(lambda+45)

R ~ size scale of your map. You will presumably have to calibrate it using known coordinates, e.g. Svalbard.