I like that you give the formula for the X-coordinate of a point on the Apianus II map, in terms of latitude. But, in the denominator, outside the square-root, shouldn’t that be Pi squared instead of just Pi?
X = 2*Lambda/Pi^2 * Sqrt(Pi^2 / 4 - phi^2)
And why not give the formula for the Y coordinate in terms of latitude:
Y = phi/Pi.
…where latitude (phi) & longitude (Lambda) are in radians, & the coordinates are expressed in terms of the height of the elliptical Apianus II map.
@RumplestiltskinCarto This is a user contributed notebook, and the author is unlikely to notice your post here. I recommend to leave a comment on the notebook itself and/or submit a suggestion with your corrections.
This is part of Observable’s notebook functionality itself. If you hover your mouse over left edge of a cell, you should see an icon popup that you can click on to leave a comment. Of course, you need to be signed in to do so.