On Wed, Oct 06, 2004 at 08:52:55 +0200, Holger Klawitter <[EMAIL PROTECTED]> wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On Sunday 03 October 2004 20:22, Bruno Wolff III wrote: > > Latitudes greater than 90 degrees have a reasonable > > meaning and it can be useful to use 0 to 180 instead of -90 to 90. > > Just a curious question: What is 100°N latitude supposed to mean?
It means 80 degrees north and longitude + 180 degrees. I shouldn't have used 0 to 180 as the example for latitude, because it really needs to range from 0 to 360, since 0 to 180 is all in the northern hemisphere. Longitude works similarly in that you can use 0 to 360 instead of -180 to +180. The advantage of this is that your application can do things like add degrees to a position and not have to check for wrapping around. You can get similar issues due to rounding after switching coordinate systems where you might get a value slightly greater than 90 degrees for latitude or get a value slightly greater than 180 degrees for longitude. As long as the principal values are returned when going from cartesian coordinates (which is how earth distance stores points) to latitude and longitude accepting values outside of the principal ones when going from spherical coordinates to cartesian coordinates isn't a problem. ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
