#   Copyright (C) 1996 Thomas R. Metcalf
#
#   This software is provided "as is" and is subject to change without
#   notice.  No warranty of any kind is made with regard to this software,
#   including, but not limited to, the implied warranties of
#   merchantability and fitness for a particular purpose.  The author shall
#   not be liable for any errors or for direct, indirect, special,
#   incidental or consequential damages in connection with the furnishing,
#   performance, or use of this software:  use it at your own risk.
#
#    This program is free software; you can redistribute it and/or
#    modify it under the terms of the GNU General Public
#    License as published by the Free Software Foundation; either
#    version 2 of the License, or (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
#    General Public License for more details.
#
#    You should have received a copy of the GNU General Public
#    License along with this library; if not, write to the Free
#    Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
#


sub ACOS {

# Compute the arc cosine
# Input: Cosine (forced to -1 <= cosine <= 1)
# Output: Angle in radians (0<angle<pi)

   my($cosine) = @_;
   my($argument);
   $argument = 1.0-$cosine**2;
   if ($argument<=0) {
      if ($cosine > 0) {0;} else {$pi;}
   } else {
      $piover2 - atan2($cosine/(sqrt($argument)),1);
   }
}

sub tan { sin($_[0]) / cos($_[0]) }


sub GCDISTANCE {

# Compute Great Circle distance between positions
# Input:  lat1, lon1, lat2, lon, all in decimal degrees
# Output: Distance in Nautical Miles, Initial Course

   my($latitude1,$longitude1,$latitude2,$longitude2) = @_;

   $latitude1 *= $dtor;
   $latitude2 *= $dtor;
   $longitude1 *= $dtor;
   $longitude2 *= $dtor;

   my $dlon = $longitude1-$longitude2;

   (&ACOS(sin($latitude1)*sin($latitude2) + 
         cos($latitude1)*cos($latitude2) *
         cos($dlon))*60/$dtor,
    atan2(sin($dlon),
          cos($latitude1)*tan($latitude2)-sin($latitude1)*cos($dlon))/$dtor);
}

sub LOCATIONS {
  my %locations;
  $locations{""} = "";
  $locations{"Acapulco, Mexico"} 	= "+16.50 +099.56 NEP 99999";
  $locations{"Agana, Guam"} 		= "+13.29 -144.48 NWP 99999";
  $locations{"Ahmenabad, India"}	= "+23.02 -072.35 NIN 99999";
  $locations{"Apalachicola, FL"}	= "+29.43 +085.01 NAT   250";
  $locations{"Atlantic City, NJ"} 	= "+39.45 +074.57 NAT 99999";
  $locations{"Auckland, New Zealand"} 	= "-37.01 -174.48 SWP 99999";
  $locations{"Baguio City, Philippines"}= "+16.25 -120.36 NWP   250";
  $locations{"Balboa, Panama"}          = "+08.57 +079.34 NEP   500";
  $locations{"Baltimore, MD"}		= "+39.11 +076.40 NAT   250";
  $locations{"Bangkok, Thailand"} 	= "+13.23 -100.36 NIN 99999";
  $locations{"Barahona, Dom. Rep."}	= "+18.13 +071.06 NAT   250";
  $locations{"Baton Rouge, LA"}		= "+30.30 +091.10 NAT   250";
  $locations{"Beaumont, TX"}		= "+30.00 +094.00 NAT   250";
  $locations{"Beef Island, BVI"}	= "+18.27 +064.32 NAT 99999";
  $locations{"Biloxi, MS"} 		= "+30.24 +088.55 NAT 99999";
  $locations{"Boca Raton, FL"}		= "+26.23 +080.09 NAT   250";
  $locations{"Bombay, India"} 		= "+19.07 -072.51 NIN 99999";
  $locations{"Boston, MA"} 		= "+42.00 +071.00 NAT 99999";
  $locations{"Bridgetown, Barbados"}	= "+13.06 +059.36 NAT 99999";
  $locations{"Broome, Australia"}       = "-17.56 -122.10 SIN 99999";
  $locations{"Brownsville, TX"} 	= "+25.54 +097.30 NAT 99999";
  $locations{"Cabo San Lucas, Mexico"} 	= "+22.52 +109.54 NEP 99999";
  $locations{"Cairns, Australia"}	= "-16.53 -145.45 SWP 99999";
  $locations{"Calcutta, India"}		= "+22.32 -088.20 NIN 99999";
  $locations{"Campeche, Mexico"}	= "+19.51 +090.33 NAT   250";
  $locations{"Cancun, Mexico"} 		= "+21.09 +086.45 NAT 99999";
  $locations{"Caracas, Venezuela"}	= "+10.36 +066.59 NAT 99999";
  $locations{"Cebu City, Philippines"} 	= "+10.18 -123.54 NWP 99999";
  $locations{"Charleston, SC"} 		= "+32.47 +079.55 NAT 99999";
  $locations{"Chittagong, Bangledesh"}	= "+22.21 -091.50 NIN 99999";
  $locations{"Coatzacoalcos, Mexico"}	= "+18.09 +094.25 NAT 99999";
  $locations{"Colon, Panama"}           = "+09.22 +079.54 NAT   500";
  $locations{"Da Nang, Vietnam"}	= "+16.04 -108.13 NWP 99999";
  $locations{"Diego Garcia"} 		= "-07.18 -072.24 SIN 99999";
  $locations{"Fort de France, Martinique"}= "+14.37 +061.05 NAT 99999";
  $locations{"Freeport, Bahamas"} 	= "+26.33 +078.42 NAT 99999";
  $locations{"Galveston, TX"} 		= "+29.17 +094.48 NAT 99999";
  $locations{"George Town, Malaysia"}	= "+05.25 -100.20 NIN 99999";
  $locations{"Grand Cayman, Cayman Is."}= "+19.17 +081.21 NAT 99999";
  $locations{"Guantanamo Bay, Cuba"}	= "+19.54 +075.09 NAT 99999";
  $locations{"Guatemala City, Guatemala"}= "+14.37 +090.31 NEP 99999";
  $locations{"Halifax, Nova Scotia"}	= "+44.40 +063.35 NAT 99999";
  $locations{"Hamilton, Bermuda"} 	= "+32.00 +064.00 NAT 99999";
  $locations{"Hamilton, New Zealand"} 	= "-37.51 -175.20 SWP 99999";
  $locations{"Hanoi, Vietnam"}		= "+21.02 -105.52 NWP 99999";
  $locations{"Havana, Cuba"} 		= "+23.07 +082.25 NAT 99999";
  $locations{"Hartford, CN"} 		= "+41.56 +072.41 NAT 99999";
  $locations{"Hilo, HI"}		= "+19.43 +155.04 NEP   250";
  $locations{"Ho Chi Minh, Vietnam"}	= "+10.47 -106.42 NWP 99999";
  $locations{"Hong Kong"} 		= "+22.30 -114.18 NWP 99999";
  $locations{"Honolulu, HI"} 		= "+21.21 +157.56 CNP 99999";
  $locations{"Jacksonville, FL"} 	= "+30.03 +081.42 NAT 99999";
  $locations{"Kadena AB, Okinawa"} 	= "+26.21 -127.46 NWP 99999";
  $locations{"Kagoshima, Japan"} 	= "+31.33 -130.33 NWP 99999";
  $locations{"Kahului, HI"}		= "+20.54 +156.26 NEP   250";
  $locations{"Karachi, Pakistan"}	= "+24.48 -066.59 NIN 99999";
  $locations{"Kennedy S.C., FL"} 	= "+28.62 +080.68 NAT 99999";
  $locations{"Key West, FL"} 		= "+24.33 +081.45 NAT 99999";
  $locations{"Kingston, Jamaica"} 	= "+17.58 +076.48 NAT 99999";
  $locations{"Kitty Hawk, NC"}          = "+36.06 +075.42 NAT   250";
  $locations{"Kona, HI"}		= "+20.38 +156.00 NEP   250";
  $locations{"Kuala Terengganu, Malaysia"} = "+05.20 -103.08 NWP 99999";
  $locations{"Maracaibo, Venezuela"}	= "+10.39 +071.36 NAT 99999";
  $locations{"Mazatlan, Mexico"} 	= "+23.12 +106.25 NEP 99999";
  $locations{"Melbourne, FL"}		= "+28.04 +080.36 NAT   250";
  $locations{"Kwajalein, Marshall Is."} = "+08.44 -167.44 NWP 99999";
  $locations{"Lajes, Azores"}		= "+38.45 +027.05 NAT 99999";
  $locations{"La Paz, Mexico"}		= "+24.16 +110.25 NEP   250";
  $locations{"Lihue, HI"}		= "+21.59 +159.21 NEP   250";
  $locations{"Limon, Costa Rica"}	= "+10.00 +083.02 NAT   500";
  $locations{"Managua, Nicaragua"}	= "+12.10 +086.15 NEP   500";
  $locations{"Manila, Philippines"} 	= "+14.35 -120.59 NWP 99999";
  $locations{"Manzanillo, Mexico"}	= "+19.03 +104.20 NEP   250";
  $locations{"Miami, FL"} 		= "+25.45 +080.23 NAT 99999";
  $locations{"Mobile, AL"} 		= "+30.40 +088.05 NAT 99999";
  $locations{"Nantucket, MA"}		= "+41.17 +070.05 NAT   250";
  $locations{"Nassau, Bahamas"} 	= "+25.03 +077.28 NAT 99999";
  $locations{"New Orleans, LA"}		= "+30.00 +090.03 NAT 99999";
  $locations{"New York, NY"} 		= "+40.39 +073.47 NAT 99999";
  $locations{"Norfolk, VA"} 		= "+36.54 +076.12 NAT 99999";
  $locations{"Ocean City, MD"} 		= "+38.20 +075.05 NAT 99999";
  $locations{"Panama City, FL"}		= "+30.10 +085.41 NAT   250";
  $locations{"Pensacola, FL"} 		= "+30.26 +087.12 NAT 99999";
  $locations{"Perth, Australia"} 	= "-31.56 -115.57 SIN 99999";
  $locations{"Plaisance, Mauritius"}	= "-20.26 -057.40 SIN   250";
  $locations{"Port Au Prince, Haiti"}	= "+18.33 +072.20 NAT 99999";
  $locations{"Port Hedland, Australia"}	= "-20.19 -118.35 SIN   250";
  $locations{"Port Louis, Mauritius"} 	= "-20.00 -057.00 SIN 99999";
  $locations{"Port of Spain, Trinidad"} = "+10.40 +061.31 NAT 99999";
  $locations{"Puerto Cortes, Honduras"}	= "+15.48 +087.56 NAT   500";
  $locations{"Puerto Vallarta, Mexico"}	= "+20.40 +105.15 NEP 99999";
  $locations{"Puerto Lempira, Honduras"}= "+15.13 +083.47 NAT   500";
  $locations{"Pyongyang, Korea"}	= "+39.02 -125.41 NWP 99999";
  $locations{"Rangoon, Burma"}		= "+16.47 -096.09 NIN 99999";
  $locations{"Saint Pierre, Reunion"} 	= "-21.20 -055.29 SIN 99999";
  $locations{"Saipan, N. Mariana Is."}	= "+15.10 -145.40 NWP 99999";
  $locations{"Salina Cruz, Mexico"}	= "+16.10 +095.12 NEP 99999";
  $locations{"San Diego, CA"} 		= "+32.51 +117.07 NEP   500";
  $locations{"San Jose, Costa Rica"}	= "+09.56 +084.05 NEP   500";
  $locations{"San Juan, Puerto Rico"}	= "+18.29 +066.08 NAT 99999";
  $locations{"Santo Domingo, Dom. Rep."}= "+18.26 +069.40 NAT 99999";
  $locations{"San Salvador, El Salvador"}= "+13.42 +089.13 NEP 99999";
  $locations{"Savannah, GA"} 		= "+32.08 +081.12 NAT 99999";
  $locations{"Seoul, Korea"}		= "+37.34 -126.58 NWP 99999";
  $locations{"St. Thomas, USVI"} 	= "+18.20 +064.58 NAT 99999";
  $locations{"Subic Bay, Philippines"}	= "+14.48 -120.16 NWP 99999";
  $locations{"Sydney, Australia"}	= "-33.52 -151.12 SWP 99999";
  $locations{"Taipei, Taiwan"} 		= "+25.20 -121.31 NWP 99999";
  $locations{"Tampico, Mexico"}		= "+22.18 +097.52 NAT 99999";
  $locations{"Tehuantepec, Mexico"}	= "+16.20 +095.14 NEP    60";
  $locations{"Tokyo, Japan"}		= "+35.33 -139.47 NWP 99999";
  $locations{"Townsville, Australia"} 	= "-19.15 -146.45 SWP 99999";
  $locations{"Wellington, New Zealand"} = "-41.20 -174.48 SWP 99999";
  $locations{"Wilmington, NC"}		= "+34.10 +077.50 NAT 99999";
  $locations{"Yap, Caroline Is."} 	= "+09.29 -138.05 NWP 99999";
  %locations;
}

sub DEG2DIRECTION {
   my ($c) = @_;
   my $tcourse;

   while ($c > 180) {$c -= 360;}
   while ($c < -180) {$c += 360;}

   if ($c > -11.25 && $c <= +11.25) {$tcourse = "N";}
   if ($c > +11.25 && $c <= +33.75) {$tcourse = "NNE";}
   if ($c > +33.75 && $c <= +56.25) {$tcourse = "NE";}
   if ($c > +56.25 && $c <= +78.75) {$tcourse = "ENE";}
   if ($c > +78.75 && $c <= +101.75) {$tcourse = "E";}
   if ($c > +101.75 && $c <= +123.75) {$tcourse = "ESE";}
   if ($c > +123.75 && $c <= +146.25) {$tcourse = "SE";}
   if ($c > +146.25 && $c <= +168.75) {$tcourse = "SSE";}
   if ($c > +168.75 || $c <= -168.75) {$tcourse = "S";}
   if ($c <= -146.25 && $c > -168.75) {$tcourse = "SSW";}
   if ($c <= -123.75 && $c > -146.25) {$tcourse = "SW";}
   if ($c <= -101.25 && $c > -123.75) {$tcourse = "WSW";}
   if ($c <= -78.75 && $c > -101.25) {$tcourse = "W";}
   if ($c <= -56.25 && $c > -78.75) {$tcourse = "WNW";}
   if ($c <= -33.75 && $c > -56.25) {$tcourse = "NW";}
   if ($c <= -11.25 && $c > -33.75) {$tcourse = "NNW";}
   #print "$c $tcourse\n";

   $tcourse;
}

sub GetLocString {
   my($lat,$lon) = @_;
   my $dmin = 999999.;
   my $locstring = "";
   my $locstring1 = "";
   my $locstringtemp= "";
   my $location,$obest,%secondbest,%dminsecond;
   foreach $location (keys(%locations)) {
      my ($lat,$lon,$o,$dthresh) = split(/\s+/,$locations{$location},4);
      $lat = int($lat) + ($lat-int($lat))*100.0/60.0;
      $lon = int($lon) + ($lon-int($lon))*100.0/60.0;
      my ($d,$c) = &GCDISTANCE($lat,$lon,$latnum,$lonnum);
      if ($d < $dthresh) {
         my $tcourse = &DEG2DIRECTION($c);
         my $dint = int($d + 0.5);
         my $locstringtemp = "$dint nmi $tcourse of $location";
         if ($obest eq "" || $d < $dmin) {
            # save old as the second best
            if ($obest ne "") {
               $secondbest{$obest} = $locstring;
               $dminsecond{$obest} = $dmin;
            }
            # set up best
            $dmin = $d;
            $obest = $o;
            $locstring = $locstringtemp;
         } elsif ($secondbest{$o} eq "" || $d < $dminsecond{$o}) {
            $secondbest{$o} = $locstringtemp;
            $dminsecond{$o} = $d;
         }
      }
   }
   $locstring1 = $secondbest{$obest};
   ($locstring,$locstring1);
}

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