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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!!!!!!
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))
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yan-foto commented Jun 22, 2018

It might be obvious, but for the sake of completeness:

import "math"

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