// Bearing takes two points and finds the geographic bearing between them.
func Bearing(point1, point2 *Point) float64 {
lat1 := turfgoMath.DegreeToRad(point1.Lat)
lat2 := turfgoMath.DegreeToRad(point2.Lat)
lon1 := turfgoMath.DegreeToRad(point1.Lng)
lon2 := turfgoMath.DegreeToRad(point2.Lng)
a := math.Sin(lon2-lon1) * math.Cos(lat2)
b := math.Cos(lat1)*math.Sin(lat2) -
math.Sin(lat1)*math.Cos(lat2)*math.Cos(lon2-lon1)
return turfgoMath.RadToDegree(math.Atan2(a, b))
}
// Distance calculates the distance between two points in degress, radians, miles, or
// kilometers. This uses the Haversine formula to account for global curvature.
func Distance(point1 *Point, point2 *Point, unit string) (float64, error) {
radius, ok := R[unit]
if !ok {
return 0, fmt.Errorf(unitError, unit)
}
dLat := turfgoMath.DegreeToRad(point2.Lat - point1.Lat)
dLon := turfgoMath.DegreeToRad(point2.Lng - point1.Lng)
latRad1 := turfgoMath.DegreeToRad(point1.Lat)
latRad2 := turfgoMath.DegreeToRad(point2.Lat)
a := math.Sin(dLat/2)*math.Sin(dLat/2) +
math.Sin(dLon/2)*math.Sin(dLon/2)*math.Cos(latRad1)*math.Cos(latRad2)
c := 2 * math.Atan2(math.Sqrt(a), math.Sqrt(1-a))
return radius * c, nil
}
// Destination takes a Point and calculates the location of a destination point
// given a distance in degrees, radians, miles, or kilometers; and bearing in
// degrees. This uses the Haversine formula to account for global curvature.
func Destination(startingPoint *Point, distance float64, bearing float64, unit string) (*Point, error) {
radius, ok := R[unit]
if !ok {
return nil, fmt.Errorf(unitError, unit)
}
lat := turfgoMath.DegreeToRad(startingPoint.Lat)
lon := turfgoMath.DegreeToRad(startingPoint.Lng)
bearingRad := turfgoMath.DegreeToRad(bearing)
destLat := math.Asin(math.Sin(lat)*math.Cos(distance/radius) +
math.Cos(lat)*math.Sin(distance/radius)*math.Cos(bearingRad))
destLon := lon + math.Atan2(math.Sin(bearingRad)*math.Sin(distance/radius)*math.Cos(lat),
math.Cos(distance/radius)-math.Sin(lat)*math.Sin(destLat))
return &Point{turfgoMath.RadToDegree(destLat), turfgoMath.RadToDegree(destLon)}, nil
}
func translate(point *Point, horizontalDisplacement float64, verticalDisplacement float64) *Point {
latDisplacementRad := verticalDisplacement / R["m"]
longDisplacementRad := horizontalDisplacement / (R["m"] * math.Cos(turfgoMath.DegreeToRad(point.Lat)))
latDisplacement := turfgoMath.RadToDegree(latDisplacementRad)
longDisplacement := turfgoMath.RadToDegree(longDisplacementRad)
translatedPoint := NewPoint(point.Lat+latDisplacement, point.Lng+longDisplacement)
return translatedPoint
}
