Re^4: Calculate aircraft headings from GPS data for google kml display

Awesome man, thanks for the tips, that's very helpful !

However, i have few more questions regarding your clever code, :-)!

first, what does following few lines of code do ? i think the first one is to trim the raw data and put it into array, but i never saw lots of expressions you put there before, can you give a bit hint, especially the # at the end, :-)!

my @headers = split ' ', do{ my $raw = <DATA>; $raw =~ tr[",][ ]; $raw
+ }; #"
$line =~ tr[",][ ]; #"
push @{ $planes{ $aid } }, \%row;

next unless @{ $planes{ $aid } } > 1;
[download]

second, i understand the key method is to get it into a hash dictionary, by using:

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

But this does not seem to pick up the right number, i did a printf to check, it seems always 0.

third, for the heading calculations, i think the math is fine, because the data represents the aircrafts at the take-off or landing stage, so most of heading should be 90 or 180 degree. also i don't need it to be that accurate, it's only for display purpose on the google earth. i did a check on one pair of coordinates by using your formula, it seems work fine.

    my $lats1=51.4774704;
    my $lats2=51.4774704;
    my $lons1=-0.458850861;
    my $lons2=-0.459365845;
    my $dlats = $lats2 - $lats1;
    my $dlons= $lons2 - $lons1;
    
    my $y1 = sin( $dlons / 180 ) * cos( $lats2 /180 );
    my $x1 = cos( $lats1 /180 ) * sin( $lats2/180 ) - sin( $lats1/180 
+) * cos( $lats2/180 ) * cos( $dlons/180 );
    
    printf  "heading: %d\n", atan2( $y1, $x1 ) * 57.2957795
[download]

I also upload more data here, in case you want to check !

_Data_

"rowid","aircraft_id","actual_date_time","latitude","longitude","radio
+_altitude","ground_speed","thrust_engine_1","thrust_engine_2","co2","
+nox"
11782888,685,2012-11-04 15:25:14,51.4774704,-0.458850861,-9.25,64.5,0.
+028000256,0.028713875,1.577894599,22.32443440
11782889,721,2012-11-04 15:25:15,51.47083282,-0.478762537,-7.0,0.0,0.0
+2504996,0.029270458,2.672078122,25.016723749
11782890,685,2012-11-04 15:25:15,51.4774704,-0.459365845,-9.5,60.75,0.
+028000256,0.029427142,1.590756897,22.13159408
11782891,709,2012-11-04 15:25:15,51.46648407,-0.468292236,-9.5,15.25,0
+.077369954,0.068239666,4.124230104,28.73529887
11782892,704,2012-11-04 15:25:15,51.46665573,-0.442199707,-9.0,0.75,0.
+033609102,0.033609102,2.074123446,51.09631094
11782893,721,2012-11-04 15:25:16,51.47083282,-0.478762537,-7.0,0.0,0.0
+2504996,0.029270458,2.678124860,24.952298408
11782894,704,2012-11-04 15:25:16,51.46665573,-0.442199707,-9.0,0.75,0.
+033609102,0.033609102,2.074123446,51.09631094
11782895,685,2012-11-04 15:25:16,51.4774704,-0.459880829,-9.5,57.25,0.
+028713875,0.029427142,1.603534644,21.93343790
11782896,709,2012-11-04 15:25:16,51.46648407,-0.468292236,-9.5,15.25,0
+.077369954,0.068239666,4.124230104,28.73529887
11782897,721,2012-11-04 15:25:17,51.47083282,-0.478762537,-7.0,0.0,0.0
+2504996,0.029270458,2.678553119,24.966366785
11782898,685,2012-11-04 15:25:17,51.4774704,-0.460224152,-9.5,54.0,0.0
+28713875,0.029427142,1.603534644,21.93343790
11782899,709,2012-11-04 15:25:17,51.46648407,-0.468120575,-9.25,15.5,0
+.077369954,0.068239666,4.124230104,28.73529887
11782900,704,2012-11-04 15:25:17,51.46665573,-0.442199707,-9.0,0.75,0.
+033609102,0.033609102,2.074123446,51.09631094
11782901,721,2012-11-04 15:25:18,51.47083282,-0.478762537,-7.0,0.0,0.0
+25653887,0.029270458,2.684827917,24.909981212
11782902,685,2012-11-04 15:25:18,51.4774704,-0.460567474,-9.5,50.5,0.0
+28713875,0.030140059,1.616481248,21.74572268
11782903,704,2012-11-04 15:25:18,51.46665573,-0.442199707,-9.0,0.75,0.
+033609102,0.033609102,2.074123446,51.09631094
11782904,709,2012-11-04 15:25:18,51.46648407,-0.467948914,-9.0,15.75,0
+.076671196,0.068239666,4.101445938,28.85420529
11782905,721,2012-11-04 15:25:19,51.47083282,-0.478762537,-7.0,0.0,0.0
+25653887,0.028668525,2.684902618,24.912091811
11782906,709,2012-11-04 15:25:19,51.46648407,-0.467948914,-9.0,16.0,0.
+076671196,0.068239666,4.101445938,28.85420529
11782907,704,2012-11-04 15:25:19,51.46665573,-0.442199707,-9.0,0.75,0.
+033609102,0.033609102,2.074123446,51.09631094
11782908,685,2012-11-04 15:25:19,51.4774704,-0.460910797,-9.5,47.25,0.
+029427142,0.030852625,1.642374213,21.37011001
11782909,721,2012-11-04 15:25:20,51.47083282,-0.478762537,-7.0,0.0,0.0
+2625748,0.028668525,2.722969965,24.583642373
11782910,709,2012-11-04 15:25:20,51.46648407,-0.467777252,-9.0,16.5,0.
+076671196,0.068239666,4.101445938,28.85420529
11782911,704,2012-11-04 15:25:20,51.46665573,-0.442199707,-9.0,0.75,0.
+033609102,0.033609102,2.074123446,51.09631094
11782912,685,2012-11-04 15:25:20,51.4774704,-0.46125412,-9.5,44.5,0.02
+9427142,0.030852625,1.642374213,21.37011001
11782913,721,2012-11-04 15:25:21,51.47083282,-0.478762537,-7.0,0.0,0.0
+28066262,0.029270458,2.781087133,24.122891683
11782914,709,2012-11-04 15:25:21,51.46648407,-0.467605591,-9.25,16.5,0
+.076671196,0.068239666,4.101445938,28.85420529
11782915,685,2012-11-04 15:25:21,51.4774704,-0.461597443,-9.5,41.75,0.
+029427142,0.030852625,1.642374213,21.37011001
11782916,704,2012-11-04 15:25:21,51.46665573,-0.442199707,-9.0,0.75,0.
+033609102,0.033609102,2.074123446,51.09631094
11782917,721,2012-11-04 15:25:22,51.47083282,-0.478762537,-7.0,0.0,0.0
+2987206,0.02987206,2.826355438,23.766313359
11782918,685,2012-11-04 15:25:22,51.4774704,-0.461940765,-9.5,39.5,0.0
+30140059,0.030852625,1.655320817,21.18239479
11782919,704,2012-11-04 15:25:22,51.46665573,-0.442199707,-9.0,0.75,0.
+033609102,0.033609102,2.074123446,51.09631094
11782920,709,2012-11-04 15:25:22,51.46648407,-0.467433929,-9.25,16.75,
+0.076671196,0.068945601,4.122771027,28.71316579
11782921,721,2012-11-04 15:25:23,51.47083282,-0.478762537,-7.0,0.0,0.0
+3167489,0.031074276,2.878496092,23.370307854
11782922,709,2012-11-04 15:25:23,51.46648407,-0.467433929,-9.0,17.0,0.
+077369954,0.068945601,4.145555193,28.59425937
11782923,685,2012-11-04 15:25:23,51.4774704,-0.462284088,-9.75,37.25,0
+.030140059,0.030852625,1.655320817,21.18239479
11782924,704,2012-11-04 15:25:23,51.46665573,-0.442199707,-9.0,0.75,0.
+033609102,0.033609102,2.074123446,51.09631094
11782925,721,2012-11-04 15:25:24,51.47083282,-0.478762537,-7.0,0.0,0.0
+3167489,0.03167489,2.891194602,23.261540959
11782926,685,2012-11-04 15:25:24,51.4774704,-0.46245575,-9.75,35.5,0.0
+29427142,0.031564842,1.655488701,21.19210642
11782927,704,2012-11-04 15:25:24,51.46665573,-0.442199707,-9.0,0.75,0.
+033609102,0.033609102,2.074123446,51.09631094
11782928,709,2012-11-04 15:25:24,51.46648407,-0.467262268,-9.25,17.5,0
+.077369954,0.068239666,4.124230104,28.73529887
11782929,721,2012-11-04 15:25:25,51.47083282,-0.478762537,-7.0,0.0,0.0
+3167489,0.032875134,2.897547209,23.208410778
11782930,704,2012-11-04 15:25:25,51.46665573,-0.442199707,-9.0,0.75,0.
+033609102,0.033609102,2.074123446,51.09631094
11782931,685,2012-11-04 15:25:25,51.4774704,-0.462799072,-9.5,34.5,0.0
+29427142,0.031564842,1.655488701,21.19210642
11782932,709,2012-11-04 15:25:25,51.46648407,-0.467090607,-9.25,17.75,
+0.077369954,0.068239666,4.124230104,28.73529887
11782933,721,2012-11-04 15:25:26,51.47083282,-0.478762537,-7.0,0.0,0.0
+3167489,0.033474765,2.904146185,23.161377706
11782934,704,2012-11-04 15:25:26,51.46665573,-0.442199707,-9.0,0.75,0.
+033609102,0.033609102,2.074123446,51.09631094
11782935,685,2012-11-04 15:25:26,51.4774704,-0.462970734,-9.5,33.75,0.
+029427142,0.031564842,1.655488701,21.19210642
11782936,709,2012-11-04 15:25:26,51.46648407,-0.467090607,-9.25,18.0,0
+.077369954,0.068239666,4.124230104,28.73529887
11782937,721,2012-11-04 15:25:27,51.47083282,-0.478762537,-7.0,0.0,0.0
+3167489,0.033474765,2.890677441,23.248813256
11782938,709,2012-11-04 15:25:27,51.46648407,-0.466918945,-9.0,18.25,0
+.077369954,0.068945601,4.145555193,28.59425937
11782939,685,2012-11-04 15:25:27,51.4774704,-0.463142395,-9.5,32.25,0.
+029427142,0.031564842,1.655488701,21.19210642
[download]

Comment on Re^4: Calculate aircraft headings from GPS data for google kml display Select or Download Code

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Re^5: Calculate aircraft headings from GPS data for google kml display by BrowserUk (Patriarch) on Jun 10, 2014 at 21:20 UTC
can you give a bit hint, especially the # at the end, :-)! `my @headers = split ' ', do{ my $raw = <DATA>; $raw =~ tr[",][ ]; $raw }; #"` Read the header line into `$raw`; Get rid of the quotes and commas and replace with spaces; return the modified line to split and split on whitespace; The `#"` at the end is just a comment; it balances up the earlier ", and prevents it from screwing up the syntax highlighting in my editor. `$line =~ tr[",][ ]; #"` Same as above. (Though it was wrong for the rest of the lines, a C&P error correct below.) `push @{ $planes{ $aid } }, \%row;` push a reference to the hash constructed from teh most recent line into the array indexed by the aircraft id. `next unless @{ $planes{ $aid } } > 1;` If we don't have 2 or more lines (in the array) for this aircraft, we cannot calculate a bearing yet, so skip to the next line. A couple of corrections and a couple of tweaks: #! 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__ [download] With the extended dataset (still no course changes!), produces: 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 [download] With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l] [select]
Re^6: Calculate aircraft headings from GPS data for google kml display by hujunsimon (Sexton) on Jun 11, 2014 at 00:23 UTC
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	[reply] [d/l]
Re^7: Calculate aircraft headings from GPS data for google kml display by BrowserUk (Patriarch) on Jun 11, 2014 at 02:10 UTC
You're slurping the entire file into an array: `open(INPUT, $infile); my @lines = <INPUT>; close(INPUT);` [download] Which means by the time you reach where I loaded the header line: `my @headers = split ' ', do{ my $raw = <INPUT>; $raw =~ tr[",][ ]; $ra +w }; #"` [download] There is nothing left to read. Either shift the first line off of the array: `my @headers = split ' ', do{ my $raw = shift @lines; $raw =~ tr[",][ ] +; $raw }; #"` [download] Or don't slurp the file and revert to using while. With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l] [select]
Re^8: Calculate aircraft headings from GPS data for google kml display by hujunsimon (Sexton) on Jun 26, 2014 at 15:01 UTC