Haversine naive implementation

main.go

package main

import (
	"fmt"
	"math"
)

var (
	EARTH_RADIUS = 6378100.0 
)

func ToRad(angle float64) float64 {
	return angle * (math.Pi / 180.0)
}

// Original Implementation from: http://www.movable-type.co.uk/scripts/latlong.html
func Distance(lat1, lon1, lat2, lon2 float64) float64 {
	dLat := ToRad(lat2 - lat1)
	dLon := ToRad(lon2 - lon1)

	lat1Rad := ToRad(lat1)
	lat2Rad := ToRad(lat2)

	a1 := math.Sin(dLat/2) * math.Sin(dLat/2)
	a2 := math.Cos(lat1Rad) * math.Cos(lat2Rad) * math.Sin(dLon/2) * math.Sin(dLon/2)
	a := a1 + a2

	c := 2 * math.Atan2(math.Sqrt(a), math.Sqrt(1-a))

	return EARTH_RADIUS * c
}

func main() {
	fmt.Println(Distance(55.028665, 82.918797, 55.056734, 82.923219))
}