#! perl -slw
use strict;
use Data::Dump qw[ pp ];

my @headers = split ' ', do{ my $raw = <DATA>; $raw =~ tr[",][ ]; $raw }; #"

my %planes;

while( my $line = <DATA> ) {
    my @fields = split ',', $line;
    my %row; @row{ @headers } = @fields;
    my $rowid = $row{ rowid };
    my $aid = $row{ aircraft_id };
    push @{ $planes{ $aid } }, \%row;

    next unless @{ $planes{ $aid } } > 1;

    my $lat1 = $planes{ $aid }[ -2 ]{ latitude };
    my $lat2 = $planes{ $aid }[ -1 ]{ latitude };
#    print "$lat1 $lat2";
    my $dlat = $lat2 - $lat1;

    my $lon1 = $planes{ $aid }[ -2 ]{ longitude };
    my $lon2 = $planes{ $aid }[ -1 ]{ longitude };
#    print "$lon1 $lon2";
    my $dlon = $lon2 - $lon1;

    my $y = sin( $dlon /180 ) * cos( $lat2 /180 );
    my $x = cos( $lat1 /180 ) * sin( $lat2 /180 ) - sin( $lat1 /180 ) * cos( $lat2 /180 ) * cos( $dlon /180 );

    printf "Aircraft: %d heading: %6.3f\n", $aid, atan2( $y, $x ) * 57.2957795;
#    <STDIN>;
}
__DATA__

##</code><code>##

C:\test>junk53
Aircraft: 685 heading: -90.000
Aircraft: 721 heading:  0.000
Aircraft: 704 heading:  0.000
Aircraft: 685 heading: -90.000
Aircraft: 709 heading:  0.000
Aircraft: 721 heading:  0.000
Aircraft: 685 heading: -90.000
Aircraft: 709 heading: 90.000
Aircraft: 704 heading:  0.000
Aircraft: 721 heading:  0.000
Aircraft: 685 heading: -90.000
Aircraft: 704 heading:  0.000
Aircraft: 709 heading: 90.000
Aircraft: 721 heading:  0.000
Aircraft: 709 heading:  0.000
Aircraft: 704 heading:  0.000
Aircraft: 685 heading: -90.000
Aircraft: 721 heading:  0.000
Aircraft: 709 heading: 90.000
Aircraft: 704 heading:  0.000
Aircraft: 685 heading: -90.000
Aircraft: 721 heading:  0.000
Aircraft: 709 heading: 90.000
Aircraft: 685 heading: -90.000
Aircraft: 704 heading:  0.000
Aircraft: 721 heading:  0.000
Aircraft: 685 heading: -90.000
Aircraft: 704 heading:  0.000
Aircraft: 709 heading: 90.000
Aircraft: 721 heading:  0.000
Aircraft: 709 heading:  0.000
Aircraft: 685 heading: -90.000
Aircraft: 704 heading:  0.000
Aircraft: 721 heading:  0.000
Aircraft: 685 heading: -90.000
Aircraft: 704 heading:  0.000
Aircraft: 709 heading: 90.000
Aircraft: 721 heading:  0.000
Aircraft: 704 heading:  0.000
Aircraft: 685 heading: -90.000
Aircraft: 709 heading: 90.000
Aircraft: 721 heading:  0.000
Aircraft: 704 heading:  0.000
Aircraft: 685 heading: -90.000
Aircraft: 709 heading:  0.000
Aircraft: 721 heading:  0.000
Aircraft: 709 heading: 90.000
Aircraft: 685 heading: -90.000