crossTrackDistanceTo static method
Calculate the signed distance from a geographic point to the great circle defined by the start and end points, also known as cross-track distance.
The cross-track distance is the shortest distance from the point l1 to
the great circle defined by the line between start and end.
It can be negative or positive depending on whether the point is to
the left or right of the path.
l1 - The geographic point for which to calculate the cross-track
distance.
start - The starting point of the great circle path.
end - The ending point of the great circle path.
radius - (Optional) The radius of the Earth in meters. If not provided,
it defaults to the mean radius of the Earth
(approximately 6371 kilometers).
Returns the cross-track distance in meters. A positive value indicates
that the point l1 is to the right of the great circle path,
and a negative value
indicates that it is to the left.
Implementation
static num crossTrackDistanceTo(LatLng l1, LatLng start, LatLng end,
[num? radius]) {
// Calculate the radius of the Earth if not provided.
final R = radius ?? 6371e3;
// Calculate the distance between start and l1 in radians.
final distStartL1 = GeoPoints.distanceBetweenTwoGeoPoints(start, l1, R) / R;
// Calculate the initial bearing from start to l1 in radians.
final bearingStartL1 = degToRadian(
BearingBetweenTwoGeoPoints.bearingBetweenTwoGeoPoints(start, l1)
.toDouble());
// Calculate the initial bearing from start to end in radians.
final bearingStartEnd = degToRadian(
BearingBetweenTwoGeoPoints.bearingBetweenTwoGeoPoints(start, end)
.toDouble());
// Calculate the cross-track distance using the spherical law of sines.
final x = asin(sin(distStartL1) * sin(bearingStartL1 - bearingStartEnd));
// Return the cross-track distance in meters.
return x * R;
}