while working on a program to project NASA DEM data using a "flat earth" model, so that the FE proponents can see how their projection matches with views of the real earth, I had to decipher the azimuthal equidistant projection, which some FE proponents claim to be the actual form of the disk on which we reside. so I had to work out the formulas using pen and paper, because the results I was getting from their mathematical formulas seemed wrong.
while it may be specified by the statement "and the angle θ that line subtends from the vertical is the azimuth angle", I had to go through a lot of trial and error to ascertain that that meant "the prime meridian is shown by the line segment from the center of the circle down towards the bottom of the page". plus I was expecting the x and y results to be those of a unit circle, when in fact the formulae return values from 1 to π, the 180 degrees latitude from the north to the south pole; to get results from 0 to 1, which can then be mapped to screen dimensions, one must first divide x and y by pi.
Back to blog or home page
last updated 2017-06-21 00:59:58. served from tektonic.jcomeau.com