[Proj] degree to radian conversions

Charles Karney charles.karney at sri.com
Thu Aug 13 15:46:03 EST 2015

I just submitted a pull request for proj.4 to correct the values of the
constants used in degree/radian conversions.  The important change was
to use


instead of


as the value of pi/180 used to convert degrees to radians in dmstor.c.
The new value is substantial closer to the true value...

   cos(90 * .0174532925199432958) =  6.1e-17
   cos(90 * .0174532925199433)    = -3.8e-16

Needless to say, some of the tests now fail.  Particularly because
proj.4 used to round 90 deg to an illegal latitude (larger than pi/2).

However the changes for the healpix checks are inexplicably large.

It would be good if someone could figure out why the healpix results
change so much.


More information about the Proj mailing list