添加地理坐标系函数

locaxis/locaxis.go

@@ -0,0 +1,100 @@
+package locaxis
+
+import (
+	"math"
+)
+
+// WGS84坐标系：即地球坐标系，国际上通用的坐标系。
+// GCJ02坐标系：即火星坐标系，WGS84坐标系经加密后的坐标系。Google Maps，高德在用。
+// BD09坐标系：即百度坐标系，GCJ02坐标系经加密后的坐标系。
+
+const (
+	XPi    = math.Pi * 3000.0 / 180.0
+	OFFSET = 0.00669342162296594323
+	AXIS   = 6378245.0
+)
+
+// BD2GCJ 百度坐标系->火星坐标系
+func BD2GCJ(lon float64, lat float64) (float64, float64) {
+	x := lon - 0.0065
+	y := lat - 0.006
+
+	z := math.Sqrt(x*x+y*y) - 0.00002*math.Sin(y*XPi)
+	theta := math.Atan2(y, x) - 0.000003*math.Cos(x*XPi)
+
+	return z * math.Cos(theta), z * math.Sin(theta)
+}
+
+// GCJ2BD 火星坐标系->百度坐标系
+func GCJ2BD(lon, lat float64) (float64, float64) {
+	z := math.Sqrt(lon*lon+lat*lat) + 0.00002*math.Sin(lat*XPi)
+	theta := math.Atan2(lat, lon) + 0.000003*math.Cos(lon*XPi)
+
+	return z*math.Cos(theta) + 0.0065, z*math.Sin(theta) + 0.006
+}
+
+// WGS2GCJ WGS84坐标系->火星坐标系
+func WGS2GCJ(lon float64, lat float64) (float64, float64) {
+	if isOutOfChina(lon, lat) {
+		return lon, lat
+	}
+
+	return delta(lon, lat)
+}
+
+// GCJ2WGS 火星坐标系->WGS84坐标系
+func GCJ2WGS(lon float64, lat float64) (float64, float64) {
+	if isOutOfChina(lon, lat) {
+		return lon, lat
+	}
+
+	mgLon, mgLat := delta(lon, lat)
+	return lon*2 - mgLon, lat*2 - mgLat
+}
+
+// BD2WGS 百度坐标系->WGS84坐标系
+func BD2WGS(lon float64, lat float64) (float64, float64) {
+	lon, lat = BD2GCJ(lon, lat)
+	return GCJ2WGS(lon, lat)
+}
+
+// WGS2BD WGS84坐标系->百度坐标系
+func WGS2BD(lon float64, lat float64) (float64, float64) {
+	lon, lat = WGS2GCJ(lon, lat)
+	return GCJ2BD(lon, lat)
+}
+
+func delta(lon float64, lat float64) (float64, float64) {
+	dLat := transformLat(lon-105.0, lat-35.0)
+	dLon := transformLng(lon-105.0, lat-35.0)
+
+	radLat := lat / 180.0 * math.Pi
+	magic := math.Sin(radLat)
+	magic = 1 - OFFSET*magic*magic
+	sqrtMagic := math.Sqrt(magic)
+
+	dLat = (dLat * 180.0) / ((AXIS * (1 - OFFSET)) / (magic * sqrtMagic) * math.Pi)
+	dLon = (dLon * 180.0) / (AXIS / sqrtMagic * math.Cos(radLat) * math.Pi)
+
+	return lon + dLon, lat + dLat
+}
+
+func transformLat(lon float64, lat float64) float64 {
+	var ret = -100.0 + 2.0*lon + 3.0*lat + 0.2*lat*lat + 0.1*lon*lat + 0.2*math.Sqrt(math.Abs(lon))
+	ret += (20.0*math.Sin(6.0*lon*math.Pi) + 20.0*math.Sin(2.0*lon*math.Pi)) * 2.0 / 3.0
+	ret += (20.0*math.Sin(lat*math.Pi) + 40.0*math.Sin(lat/3.0*math.Pi)) * 2.0 / 3.0
+	ret += (160.0*math.Sin(lat/12.0*math.Pi) + 320*math.Sin(lat*math.Pi/30.0)) * 2.0 / 3.0
+	return ret
+}
+
+func transformLng(lon float64, lat float64) float64 {
+	var ret = 300.0 + lon + 2.0*lat + 0.1*lon*lon + 0.1*lon*lat + 0.1*math.Sqrt(math.Abs(lon))
+	ret += (20.0*math.Sin(6.0*lon*math.Pi) + 20.0*math.Sin(2.0*lon*math.Pi)) * 2.0 / 3.0
+	ret += (20.0*math.Sin(lon*math.Pi) + 40.0*math.Sin(lon/3.0*math.Pi)) * 2.0 / 3.0
+	ret += (150.0*math.Sin(lon/12.0*math.Pi) + 300.0*math.Sin(lon/30.0*math.Pi)) * 2.0 / 3.0
+	return ret
+}
+
+func isOutOfChina(lon float64, lat float64) bool {
+	return !(lon > 73.66 && lon < 135.05 && lat > 3.86 && lat < 53.55)
+}