intersectionByPaths method

Coordinate? intersectionByPaths(Coordinate l1, Coordinate l2, num b1, num b2,)

calculate the geo point of intersection of two given paths

Implementation

Coordinate? intersectionByPaths(
    Coordinate l1, Coordinate l2, num b1, num b2) {
  num l1LatRadians = degToRadian(l1.y);
  num l1LngRadians = degToRadian(l1.x);
  num l2LatRadians = degToRadian(l2.y);
  num l2LngRadians = degToRadian(l2.x);
  num b1Radians = degToRadian(b1 as double);
  num b2Radians = degToRadian(b2 as double);
  var latRadiansDiff = l2LatRadians - l1LatRadians;
  var lngRadiansDiff = l2LngRadians - l1LngRadians;

  num angularDistance = 2 *
      math.asin(math.sqrt(
          math.sin(latRadiansDiff / 2) * math.sin(latRadiansDiff / 2) +
              math.cos(l1LatRadians) *
                  math.cos(l2LatRadians) *
                  math.sin(lngRadiansDiff / 2) *
                  math.sin(lngRadiansDiff / 2)));
  if (angularDistance == 0) return null;

  num initBearingX = math.acos((math.sin(l2LatRadians) -
          math.sin(l1LatRadians) * math.cos(angularDistance)) /
      (math.sin(angularDistance) * math.cos(l1LatRadians)));
  if (initBearingX.isNaN) initBearingX = 0;
  num initBearingY = math.acos((math.sin(l1LatRadians) -
          math.sin(l2LatRadians) * math.cos(angularDistance)) /
      (math.sin(angularDistance) * math.cos(l2LatRadians)));

  var finalBearingX = math.sin(l2LngRadians - l1LngRadians) > 0
      ? initBearingX
      : 2 * _PI - initBearingX;
  var finalBearingY = math.sin(l2LngRadians - l1LngRadians) > 0
      ? 2 * _PI - initBearingY
      : initBearingY;

  var angle1 = b1Radians - finalBearingX;
  var angle2 = finalBearingY - b2Radians;

  if (math.sin(angle1) == 0 && math.sin(angle2) == 0) return null;
  if (math.sin(angle1) * math.sin(angle2) < 0) return null;

  num angle3 = math.acos(-math.cos(angle1) * math.cos(angle2) +
      math.sin(angle1) * math.sin(angle2) * math.cos(angularDistance));
  num dst13 = math.atan2(
      math.sin(angularDistance) * math.sin(angle1) * math.sin(angle2),
      math.cos(angle2) + math.cos(angle1) * math.cos(angle3));
  num lat3 = math.asin(math.sin(l1LatRadians) * math.cos(dst13) +
      math.cos(l1LatRadians) * math.sin(dst13) * math.cos(b1Radians));
  num lngRadiansDiff13 = math.atan2(
      math.sin(b1Radians) * math.sin(dst13) * math.cos(l1LatRadians),
      math.cos(dst13) - math.sin(l1LatRadians) * math.sin(lat3));
  var l3LngRadians = l1LngRadians + lngRadiansDiff13;

  return Coordinate((radianToDeg(l3LngRadians as double) + 540) % 360 - 180,
      radianToDeg(lat3 as double));
}