optimize const EARTH_R

freezzj · Jun 11, 2016 · e05c227 · e05c227
1 parent 784520c
commit e05c227
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Showing 5 changed files with 18 additions and 19 deletions.
diff --git a/c/transform.c b/c/transform.c
@@ -24,6 +24,8 @@ INLINE static int outOfChina(double lat, double lng) {
 	return 0;
 }
 
+#define EARTH_R 6378245.0
+
 void transform(double x, double y, double *lat, double *lng) {
 	double xy = x * y;
 	double absX = sqrt(fabs(x));
@@ -51,15 +53,14 @@ static void delta(double lat, double lng, double *dLat, double *dLng) {
 	if ((dLat == NULL) || (dLng == NULL)) {
 		return;
 	}
-	const double a = 6378245.0;
 	const double ee = 0.00669342162296594323;
 	transform(lng-105.0, lat-35.0, dLat, dLng);
 	double radLat = lat / 180.0 * M_PI;
 	double magic = sin(radLat);
 	magic = 1 - ee*magic*magic;
 	double sqrtMagic = sqrt(magic);
-	*dLat = (*dLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * M_PI);
-	*dLng = (*dLng * 180.0) / (a / sqrtMagic * cos(radLat) * M_PI);
+	*dLat = (*dLat * 180.0) / ((EARTH_R * (1 - ee)) / (magic * sqrtMagic) * M_PI);
+	*dLng = (*dLng * 180.0) / (EARTH_R / sqrtMagic * cos(radLat) * M_PI);
 }
 
 void wgs2gcj(double wgsLat, double wgsLng, double *gcjLat, double *gcjLng) {
@@ -126,7 +127,6 @@ void gcj2wgs_exact(double gcjLat, double gcjLng, double *wgsLat, double *wgsLng)
 }
 
 double distance(double latA, double lngA, double latB, double lngB) {
-	const double earthR = 6378137;
 	double arcLatA = latA * M_PI/180;
 	double arcLatB = latB * M_PI/180;
 	double x = cos(arcLatA) * cos(arcLatB) * cos((lngA-lngB)*M_PI/180);
@@ -139,5 +139,5 @@ double distance(double latA, double lngA, double latB, double lngB) {
 		s = -1;
 	}
 	double alpha = acos(s);
-	return alpha * earthR;
+	return alpha * EARTH_R;
 }
diff --git a/javascript/test.js b/javascript/test.js
@@ -5,7 +5,7 @@ var transform = require('./transform.js');
 var tests = [
 	// wgsLat, wgsLng, gcjLat, gcjLng
 	[31.1774276, 121.5272106, 31.17530398364597, 121.531541859215], // shanghai
-	[22.543847, 113.912316, 22.540796131694766, 113.9171764808363], // shenzhen
+	[22.543847, 113.912316, 22.540796131694766, 113.9171774808363], // shenzhen
 	[39.911954, 116.377817, 39.91334545536069, 116.38404722455657] // beijing
 ];
 

diff --git a/javascript/transform.js b/javascript/transform.js
@@ -7,6 +7,8 @@ if (typeof module === "object" && exports) {
 	exports = window["eviltransform"] = {};
 }
 
+var earthR = 6378137.0;
+
 function outOfChina(lat, lng) {
 	if ((lng < 72.004) || (lng > 137.8347)) {
 		return true;
@@ -43,15 +45,14 @@ function transform(x, y) {
 }
 
 function delta(lat, lng) {
-	var a = 6378137.0;
 	var ee = 0.00669342162296594323;
 	var d = transform(lng-105.0, lat-35.0);
 	var radLat = lat / 180.0 * Math.PI;
 	var magic = Math.sin(radLat);
 	magic = 1 - ee*magic*magic;
 	var sqrtMagic = Math.sqrt(magic);
-	d.lat = (d.lat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * Math.PI);
-	d.lng = (d.lng * 180.0) / (a / sqrtMagic * Math.cos(radLat) * Math.PI);
+	d.lat = (d.lat * 180.0) / ((earthR * (1 - ee)) / (magic * sqrtMagic) * Math.PI);
+	d.lng = (d.lng * 180.0) / (earthR / sqrtMagic * Math.cos(radLat) * Math.PI);
 	return d;
 }
 
@@ -105,7 +106,6 @@ function gcj2wgs_exact(gcjLat, gcjLng) {
 exports.gcj2wgs_exact = gcj2wgs_exact;
 
 function distance(latA, lngA, latB, lngB) {
-	var earthR = 6371000;
 	var pi180 = Math.PI / 180;
 	var arcLatA = latA * pi180;
  	var arcLatB = latB * pi180;

diff --git a/python/eviltransform.py b/python/eviltransform.py
@@ -7,6 +7,7 @@
 __all__ = ['wgs2gcj', 'gcj2wgs', 'gcj2wgs_exact',
            'distance', 'gcj2bd', 'bd2gcj', 'wgs2bd', 'bd2wgs']
 
+earthR = 6378137.0
 
 def outOfChina(lat, lng):
     return not (72.004 <= lng <= 137.8347 and 0.8293 <= lat <= 55.8271)
@@ -38,15 +39,14 @@ def transform(x, y):
 
 
 def delta(lat, lng):
-    a = 6378137.0
     ee = 0.00669342162296594323
     dLat, dLng = transform(lng-105.0, lat-35.0)
     radLat = lat / 180.0 * math.pi
     magic = math.sin(radLat)
     magic = 1 - ee * magic * magic
     sqrtMagic = math.sqrt(magic)
-    dLat = (dLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * math.pi)
-    dLng = (dLng * 180.0) / (a / sqrtMagic * math.cos(radLat) * math.pi)
+    dLat = (dLat * 180.0) / ((earthR * (1 - ee)) / (magic * sqrtMagic) * math.pi)
+    dLng = (dLng * 180.0) / (earthR / sqrtMagic * math.cos(radLat) * math.pi)
     return dLat, dLng
 
 
@@ -94,7 +94,6 @@ def gcj2wgs_exact(gcjLat, gcjLng):
 
 
 def distance(latA, lngA, latB, lngB):
-    earthR = 6371000
     pi180 = math.pi / 180
     arcLatA = latA * pi180
     arcLatB = latB * pi180

diff --git a/rust/src/lib.rs b/rust/src/lib.rs
@@ -1,5 +1,7 @@
 use std::f64::consts::PI;
 
+const EARTH_R: f64 = 6378137.0;
+
 fn out_of_china(lat: f64, lng: f64) -> bool {
     if lng < 72.004 || lng > 137.8347 {
         return true
@@ -36,7 +38,6 @@ fn transform(x: f64, y: f64) -> (f64, f64) {
 }
 
 fn delta(lat: f64, lng: f64) -> (f64, f64) {
-	let a = 6378137.0;
 	let ee = 0.00669342162296594323;
 	let (d_lat, d_lng) = transform(lng-105.0, lat-35.0);
     let mut d_lat = d_lat;
@@ -45,8 +46,8 @@ fn delta(lat: f64, lng: f64) -> (f64, f64) {
 	let mut magic = (rad_lat).sin();
 	magic = 1.0 - ee*magic*magic;
 	let sqrt_magic = (magic).sqrt();
-	d_lat = (d_lat * 180.0) / ((a * (1.0 - ee)) / (magic * sqrt_magic) * PI);
-	d_lng = (d_lng * 180.0) / (a / sqrt_magic * (rad_lat).cos() * PI);
+	d_lat = (d_lat * 180.0) / ((EARTH_R * (1.0 - ee)) / (magic * sqrt_magic) * PI);
+	d_lng = (d_lng * 180.0) / (EARTH_R / sqrt_magic * (rad_lat).cos() * PI);
 	(d_lat, d_lng)
 }
 
@@ -105,7 +106,6 @@ pub fn gcj2wgs_exact(gcj_lat: f64, gcj_lng: f64) -> (f64, f64) {
 
 // distance calculate the distance between point(lat_a, lng_a) and point(lat_b, lng_b), unit in meter.
 pub fn distance(lat_a: f64, lng_a: f64, lat_b: f64, lng_b: f64) -> f64 {
-	const EARTH_R: f64 = 6371000.0;
 	let arc_lat_a = lat_a * PI / 180.0;
 	let arc_lat_b = lat_b * PI / 180.0;
 	let x = (arc_lat_a).cos() * (arc_lat_b).cos() * ((lng_a-lng_b)*PI/180.0).cos();
@@ -133,7 +133,7 @@ mod tests {
     		distance: f64,
     	}
         const TESTS: [Test; 1] = [
-    		Test{a_lat:31.17530398364597, a_lng:121.531541859215, b_lat:39.91334545536069, b_lng:116.38404722455657, distance:1076958.0}, // shanghai to beijing
+    		Test{a_lat:31.17530398364597, a_lng:121.531541859215, b_lat:39.91334545536069, b_lng:116.38404722455657, distance:1078164.0}, // shanghai to beijing
     	];
     	for test in TESTS.iter() {
     		let d = super::distance(test.a_lat, test.a_lng, test.b_lat, test.b_lng);