my $y # V, the vertical component of VH
my $x # H, the horizontal component of VH

# FUNCTION NAME: convert_geo_vh()
# INPUTS: double b (latitude)
#         double l (longitude)
# OUTPUT: double y (V, the vertical component of VH)
#         double x (H, the horizontal component of VH)
# PURPOSE:
# This function converts latitude and longitude (in radians) to
# V-H coordinates (unit of measure square root of 0.1 mile).
# This function returns V-H coordinates with two decimal places:
# VVVV.VV as the Y-coordinate and HHHH.HH as the X-coordinate.
# This is precise to only a "16.7 x 16.7"-foot square. The
# distortion inherent in a continent-wide projection makes any
# more than two decimal places meaningless. Thus, any conversion
# to or from V-H coordinates is only an approximate location.

sub convert_geo_vh() {
  my $b = shift;
  my $l = shift;

  my ($i, $v, $h);
  my ($h1, $v1, $e, $w, $e1, $w1);
  my ($xx, $yy, $zz, $p, $q);
  my ($kk, $ll, $k1, $k3, $k5, $k7, $k9);

  $k1 = 0.99435487 * $b;
  $k3 = 0.00336523 * $b * $b * $b;
  $k5 = 0.00065596 * $b * $b * $b * $b * $b;
  $k7 = 0.00005606 * $b * $b * $b * $b * $b * $b * $b;
  $k9 = 0.00000188 * $b * $b * $b * $b * $b * $b * $b * $b * $b;
  $kk = $k1 + $k3 - $k5 + $k7 - $k9;
  $xx = sin($kk);
  $ll = $l - 0.907571211;
  $yy = cos($kk) * sin($ll);
  $zz = cos($kk) * cos($ll);
  $e1 = (0.60933887 * $xx) + (0.40426992 * $yy) + (0.68210848 * $zz);
  if ($e1 > 1.0)
    $e1 = 1.0;
  $q = sqrt(fabs(1.0 - ($e1 * $e1)));
  $e = asin($q);
  $w1 = (0.6544921 * $xx) + (0.65517646 * $yy) + (0.3773379 * $zz);
  if ($w1 > 1.0)
    $w1 = 1.0;
  $q = sqrt(fabs(1.0 - ($w1 * $w1)));
  $w = asin($q);
  $h1 = (($e * $e) - ($w * $w) + 0.16) / 0.8;
  $v1 = sqrt(fabs(($e * $e) - ($h1 * $h1)));
  $i = (10.0*($xx - (0.73553336 * $yy) - (0.45738305 * $zz)) + 0.5);
  if ($i < 0)
    $i--;
  $p = $i;
  $p = $p / 100000000.0;
  if ($p < 0)
    $v1 *= -1.0;
  if ($p == 0)
    $v1 = 0.0;
  $v = ((6363.235 + (2893.0 * $h1) - (12141.19003 * $v1)) * 100.0 + 0.5);
  $h = ((2250.7 + (12141.19003 * $h1) + (2893.0 * $v1)) * 100.0 + 0.5);
  $y = $v / 100.0;
  $x = $h / 100.0;
  $c = 0.0;
  $k = 1.0;
  return;
}