Talk:Winkel Tripel projection

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What does "tripel" mean, though?

It's German for "triple". -- 85.119.130.132 13:59, 15 August 2006 (UTC)

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Tripel is a German term meaning a combination of three elements. Winkel choose the name Tripel because he had developed a compromise projection; it does not eliminate area, direction or distance distortions; rather, it tries to minimize the sum of all three AceT 11:21, 20 June 2006 (UTC)

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I had a question: Can someone help me with the symbols & structure of the formulas?
I found the answer, so it looks to me only fair to share it with you all:

The formulas: α = arccos (cos φ cos (λ/2)) w = 0 if sin α = 0 otherwise w = 1 / sin α x = R(λ cos φ0 + 2wα cos φ sin (λ/2)) / 2 y = R(φ + wα sin φ) / 2

Explanation symbols: φ0 = ±arccos 2/π (+ or -, result is the same) R = Radius ("pick a value") λ = longitude φ = latitude

For those who use Perl:
use Math::Trig qw(deg2rad pi acos);
sub winkel(){
  my ($cx,$cy,$Radius) = @_;
  my ($cxp, $cyp, $lat0, $wee, $alpha, $cxR, $cyR);
  $lat0 = acos(2/pi);

  $cxR=deg2rad($cx);
  $cyR=deg2rad(-$cy);

  $alpha = acos(cos($cyR)*cos($cxR/2));
  if ( sin($alpha) == 0 ) { $wee = 0 }
  else                         { $wee = 1/sin($alpha) }
  $cxp = $Radius*($cxR*cos($lat0) + 2*$wee*$alpha*cos($cyR)*sin($cxR/2)) / 2;
  $cyp = $Radius*($cyR + $wee*$alpha*sin($cyR)) / 2;

  return($cxp,$cyp);
}
(also with thanks to Jarkko Hietaniemi who worked on Math::Trig ) AceT 19:37, 10 July 2006 (UTC)