Added Haversine helper functions

position/haversine.go

@@ -0,0 +1,21 @@
+package position
+
+import "math"
+
+const (
+	earthRadius = float64(6371)
+)
+
+func Haversine(lonFrom float64, latFrom float64, lonTo float64, latTo float64) (distance float64) {
+	var deltaLat = (latTo - latFrom) * (math.Pi / 180)
+	var deltaLon = (lonTo - lonFrom) * (math.Pi / 180)
+
+	var a = math.Sin(deltaLat/2)*math.Sin(deltaLat/2) +
+		math.Cos(latFrom*(math.Pi/180))*math.Cos(latTo*(math.Pi/180))*
+			math.Sin(deltaLon/2)*math.Sin(deltaLon/2)
+	var c = 2 * math.Atan2(math.Sqrt(a), math.Sqrt(1-a))
+
+	distance = earthRadius * c
+
+	return
+}

position/haversine_test.go

@@ -0,0 +1,34 @@
+package position_test
+
+import (
+	. "github.com/Luzifer/go_helpers/position"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Haversine", func() {
+
+	var testCases = []struct {
+		SourceLat float64
+		SourceLon float64
+		DestLat   float64
+		DestLon   float64
+		Distance  float64
+	}{
+		{50.066389, -5.714722, 58.643889, -3.070000, 968.8535441168448},
+		{50.063995, -5.609464, 53.553027, 9.993782, 1137.894906816002},
+		{53.553027, 9.993782, 53.554528, 9.991357, 0.23133816528015647},
+		{50, 9, 51, 9, 111.19492664455873},
+		{0, 9, 0, 10, 111.19492664455873},
+		{1, 0, -1, 0, 222.38985328911747},
+	}
+
+	It("should have the documented distance", func() {
+		for i := range testCases {
+			tc := testCases[i]
+			Expect(Haversine(tc.SourceLon, tc.SourceLat, tc.DestLon, tc.DestLat)).To(Equal(tc.Distance))
+		}
+	})
+
+})

position/position_suite_test.go

@@ -0,0 +1,13 @@
+package position_test
+
+import (
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+
+	"testing"
+)
+
+func TestPosition(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "Position Suite")
+}