That is 99.99999999999999780441116897988% error. 16 9's is better than any measuring instrument in existence. I think it'll do:)
-------- Paul Anderson -- VE3HOP On 2012-08-30, at 1:29 AM, Jim Gibson <jimsgib...@gmail.com> wrote: > > On Aug 29, 2012, at 5:53 PM, Chris Stinemetz wrote: > >> Just one question. If the two sets of coordinates are the same I was >> expecting the distance to be 0 miles. >> >> Instead I get: >> >> 2.19558883102012e-013 >> >> For the following example. >> >> #!/usr/bin/perl >> >> use strict; >> use warnings; >> >> use feature qw(say); >> use Geo::Ellipsoid; >> >> my $lat1 = 39.316858; >> my $lat2 = 39.316858; >> my $lon1 = -94.963194; >> my $lon2 = -94.963194; >> >> >> my $ellipsoid = Geo::Ellipsoid->new(units=>'degrees', dist=>'miles'); >> say $ellipsoid->range($lat1,$lon1,$lat2,$lon2); >> >> If it is the expected outcome would you please explain why? > > > Because floating-point arithmetic as done by limited precision computers is > always an approximation. An IEEE 754 double-precision 64-bit floating point > number uses a 53-bit fraction and therefore has about 16 decimal digits of > precision. So calculating zero within 13 digits (e-013) is pretty good. > > The calculation done by the Geo::Ellipsoid module is very complex and > involves sines, cosines, tangents, etc. Precision will be lost with each > floating-point operation. > > Have you worked out what 2e-13 miles is in inches? For all practical > purposes, it IS zero. > > > -- > To unsubscribe, e-mail: beginners-unsubscr...@perl.org > For additional commands, e-mail: beginners-h...@perl.org > http://learn.perl.org/ > > -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
