Thank you for the excellent explanation, it all becomes quite clear !

I have made few tweak on your code and try to integrate my original code, which is to generate kml file for google display, here is my attempt, but unfortunately the code doesn't run as expected. I think the problem is at reading the file. i switch from using 'while' to 'foreach' to loop through the file, but it doesn't work. I must have done something silly. Any suggestions ?!

Also i have also replaced your 'next unless' statement to 'if', it should works the same. 

#!/usr/bin/perl
use strict;
use POSIX qw(ceil floor);

open(INPUT, $infile);
my @lines = <INPUT>;
close(INPUT);

open(OUTPUT, ">$outfile");

my $timeCounter = 0;
my $seconds = 0;
my $minutes = 0;
my $hours = 0;
my $comma = ",";
my $space = " ";

print OUTPUT "<?xml version=\"1.0\" encoding=\"UTF-8\"?>"."\n";
print OUTPUT "<kml xmlns=\"http://earth.google.com/kml/2.1\">"."\n";
print OUTPUT "<Folder>"."\n";
print OUTPUT "<LookAt><longitude>-0.45</longitude><latitude>51.4666667
+</latitude><altitude>1500</altitude><range>7000</range><tilt>65</tilt
+><heading>0</heading></LookAt>"."\n";


my @headers = split ' ', do{ my $raw = <INPUT>; $raw =~ tr[",][ ]; $ra
+w }; #"
printf @headers;
my %planes;

foreach my $currentLine(@lines)
{
    
    my @fields = split',', $currentLine;

    #--- At this point, we have the data from the current line. We nee
+d to convert this to appropriate kml elements
    
    
    my %row; @row{ @headers } = @fields;
    
    
    #--- Get all the elements
    my $rowid              = $row{rowid};
    my $aid             = $row{aircraft_id};    
    my $actual_date_time   = $row{actual_date_time};
    my $latitude           = $row{latitude};
    my $longitude          = $row{longitude}; 
    my $radio_altitude     = $row{radio_altitude};
    my $ground_speed       = $row{ground_speed};
    my $thrust_engine_1    = $row{thrust_engine_1};
    my $thrust_engine_2    = $row{thrust_engine_2};
    my $nox_total          = $row{nox_total};
    my $co_total           = $row{co_total};
    
    
    #--- Now, convert start and end times into UTC
    my @timeString = split(my $space,$actual_date_time);
    $actual_date_time = @timeString[0]."T".@timeString[1];

    #--- Determine the heading
    push @{ $planes{ $aid } }, \%row;
    
    if ( @{ $planes{ $aid} } > 1)
    {

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

    my $lon1 = $planes{ $aid }[ -2 ]{longitude};
    my $lon2 = $planes{ $aid }[ -1 ]{longitude};
    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 );
    my $heading = atan2( $y, $x ) * 57.2957795;
    }
    else 
    {
    my $heading= 0;
    }

    #--- (1) Determine the geometry
    my $icon = "./blue_plane.png";
    print OUTPUT "<Placemark><Style><IconStyle><scale>1.0</scale><head
+ing>";
    print OUTPUT my $heading;
    print OUTPUT "</heading><Icon><href>$icon</href></Icon></IconStyle
+></Style><Point><coordinates>";
    print OUTPUT $longitude.$comma.$latitude.$comma.$radio_altitude;
    print OUTPUT "</coordinates><altitudeMode>relativeToGround</altitu
+deMode></Point>";
    print OUTPUT "<TimeStamp><when>$actual_date_time</when></TimeStamp
+>";
    print OUTPUT "<description>"."ID:".$rowid."<hr/>"."time:".$actual_
+date_time."<hr/>"."Ground_speed:".$ground_speed."<hr/>"."Thrust_engin
+e_1:".$thrust_engine_1."<hr/>"."thrust_engine_2:".$thrust_engine_2."<
+hr/>"."nox_total:".$nox_total."<hr/>"."co_total:".$co_total."<hr/>"."
+longitude:".$longitude."<hr/>"."latitude:".$latitude."<hr/>"."radio_a
+ltitude:".$radio_altitude."<hr/></description>";
    print OUTPUT "</Placemark>"."\n";
    }


print OUTPUT "</Folder></kml>";

[download]

Thanks in Millions !

Si

In reply to Re^6: Calculate aircraft headings from GPS data for google kml display by hujunsimon
in thread Calculate aircraft headings from GPS data for google kml display by hujunsimon

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