distanceCoordsHaversine function Null safety

double distanceCoordsHaversine(
  1. double latADeg,
  2. double longADeg,
  3. double latBDeg,
  4. double longBDeg,
  5. {dynamic earthRadiusMeters = EarthRadiusMeters.mean}
)

Calculates the distance in meters between point A at spherical (latitude, longitude) coordinates (latADeg, longADeg) and B at (latBDeg, longBDeg) - all in degrees, using the haversine formula.

earthRadiusMeters can be used to specify a radius to be used other than the mean earth radius.

The result is very accurate for a perfectly spherical earth and has up to about 0.3% error compared to the ellipsoidal shape of the earth. Based on https://www.movable-type.co.uk/scripts/latlong.html.

Implementation

double distanceCoordsHaversine(
    double latADeg, double longADeg, double latBDeg, double longBDeg,
    {earthRadiusMeters = EarthRadiusMeters.mean}) {
  final latARad = degToRad(latADeg);
  final latBRad = degToRad(latBDeg);
  final deltaLatRad =
      degToRad(deltaLatitudeAbs(latADeg, latBDeg)); // latBRad - latARad;
  final deltaLongRad =
      degToRad(deltaLongitudeAbs(longADeg, longBDeg)); //longBDeg - longADeg);

  final sinHalfDeltaLatRad = sin(deltaLatRad / 2);
  final sinHalfDeltaLongRad = sin(deltaLongRad / 2);
  final a = sinHalfDeltaLatRad * sinHalfDeltaLatRad +
      cos(latARad) * cos(latBRad) * sinHalfDeltaLongRad * sinHalfDeltaLongRad;
  final c = 2 * atan2(sqrt(a), sqrt(1 - a));

  return earthRadiusMeters * c;
}