 kareem-h
4/15/2015 - 1:31 AM

## Golang functions to calculate the distance in meters between long,lat points on Earth.

Golang functions to calculate the distance in meters between long,lat points on Earth.

``````// haversin(θ) function
func hsin(theta float64) float64 {
return math.Pow(math.Sin(theta/2), 2)
}

// Distance function returns the distance (in meters) between two points of
//     a given longitude and latitude relatively accurately (using a spherical
//     approximation of the Earth) through the Haversin Distance Formula for
//     great arc distance on a sphere with accuracy for small distances
//
// point coordinates are supplied in degrees and converted into rad. in the func
//
// distance returned is METERS!!!!!!
// http://en.wikipedia.org/wiki/Haversine_formula
func Distance(lat1, lon1, lat2, lon2 float64) float64 {
// convert to radians
// must cast radius as float to multiply later
var la1, lo1, la2, lo2, r float64
la1 = lat1 * math.Pi / 180
lo1 = lon1 * math.Pi / 180
la2 = lat2 * math.Pi / 180
lo2 = lon2 * math.Pi / 180

r = 6378100 // Earth radius in METERS

// calculate
h := hsin(la2-la1) + math.Cos(la1)*math.Cos(la2)*hsin(lo2-lo1)

return 2 * r * math.Asin(math.Sqrt(h))
}``````