Common coordinate system

  • Wgs84 coordinate system

This is the universal international coordinate system, also known as the Earth coordinate system. GPS and Beidou system use the WGS coordinate system. Google Maps uses the WGS coordinate system (except for China), which is also used by OpenStreetMap

  • Gcj02 coordinate system

It is a coordinate system of geographic information system formulated by the State Bureau of Surveying and Mapping of China. The coordinate system encrypted by WGS84 coordinate system, also known as Mars coordinate system, is GCJ02 geographical coordinate system used by Google Map of China, Tencent map and Gaode Map.

  • BD09 coordinate system

Namely baidu coordinate system, GCJ02 coordinate system after encryption, created by Baidu, Baidu Map uses this coordinate system

The transformation code

/** * Determine whether the latitude and longitude is outside China */
function isLocationOutOfChina(latitude, longitude) {
	if (longitude < 72.004 || longitude > 137.8347 || latitude < 0.8293 || latitude > 55.8271)
	  return true;
	return false;
  }
  
  
  /** * Convert WGS-84(international standard) to GCJ-02(Mars coordinates): */
  function transformFromWGSToGCJ(latitude, longitude) {
	var lat = "";
	var lon = "";
	var ee = 0.00669342162296594323;
	var a = 6378245.0;
	var pi = 3.14159265358979324;
  
	if (isLocationOutOfChina(latitude, longitude)) {
	  lat = latitude;
	  lon = longitude;
	}
	else {
	  var adjustLat = transformLatWithXY(longitude - 105.0, latitude - 35.0);
	  var adjustLon = transformLonWithXY(longitude - 105.0, latitude - 35.0);
	  var radLat = latitude / 180.0 * pi;
	  var magic = Math.sin(radLat);
	  magic = 1 - ee * magic * magic;
	  var sqrtMagic = Math.sqrt(magic);
	  adjustLat = (adjustLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * pi);
	  adjustLon = (adjustLon * 180.0) / (a / sqrtMagic * Math.cos(radLat) * pi);
	  latitude = latitude + adjustLat;
	  longitude = longitude + adjustLon;
	}
	return { latitude: latitude, longitude: longitude };
  
  }
  
  /** * change gCJ-02 (Mars coordinates) to Baidu coordinates: */
  function transformFromGCJToBaidu(latitude, longitude) {  
	var pi = 3.14159265358979324 * 3000.0 / 180.0;
  
	var z = Math.sqrt(longitude * longitude + latitude * latitude) + 0.00002 * Math.sin(latitude * pi);
	var theta = Math.atan2(latitude, longitude) + 0.000003 * Math.cos(longitude * pi);
	var a_latitude = (z * Math.sin(theta) + 0.006);
	var a_longitude = (z * Math.cos(theta) + 0.0065);
  
	return { latitude: a_latitude, longitude: a_longitude };
  }
  
  /** * Change the baidu coordinates to GCJ-02(Mars coordinates): */
  function transformFromBaiduToGCJ(latitude, longitude) {
	var xPi = 3.14159265358979323846264338327950288 * 3000.0 / 180.0;
  
	var x = longitude - 0.0065;
	var y = latitude - 0.006;
	var z = Math.sqrt(x * x + y * y) - 0.00002 * Math.sin(y * xPi);
	var theta = Math.atan2(y, x) - 0.000003 * Math.cos(x * xPi);
	var a_latitude = z * Math.sin(theta);
	var a_longitude = z * Math.cos(theta);
  
	return { latitude: a_latitude, longitude: a_longitude };
  }
  
  /** * Change gCJ-02 (Mars coordinates) to WGS-84: */
  function transformFromGCJToWGS(latitude, longitude) {
	var threshold = 0.00001;
  
	// The boundary
	var minLat = latitude - 0.5;
	var maxLat = latitude + 0.5;
	var minLng = longitude - 0.5;
	var maxLng = longitude + 0.5;
  
	var delta = 1;
	var maxIteration = 30;
  
	while (true) {
	  var leftBottom = transformFromWGSToGCJ(minLat, minLng);
	  var rightBottom = transformFromWGSToGCJ(minLat, maxLng);
	  var leftUp = transformFromWGSToGCJ(maxLat, minLng);
	  var midPoint = transformFromWGSToGCJ((minLat + maxLat) / 2, (minLng + maxLng) / 2);
	  delta = Math.abs(midPoint.latitude - latitude) + Math.abs(midPoint.longitude - longitude);
  
	  if (maxIteration-- <= 0 || delta <= threshold) {
		return { latitude: (minLat + maxLat) / 2.longitude: (minLng + maxLng) / 2 };
	  }
  
	  if (isContains({ latitude: latitude, longitude: longitude }, leftBottom, midPoint)) {
		maxLat = (minLat + maxLat) / 2;
		maxLng = (minLng + maxLng) / 2;
	  }
	  else if (isContains({ latitude: latitude, longitude: longitude }, rightBottom, midPoint)) {
		maxLat = (minLat + maxLat) / 2;
		minLng = (minLng + maxLng) / 2;
	  }
	  else if (isContains({ latitude: latitude, longitude: longitude }, leftUp, midPoint)) {
		minLat = (minLat + maxLat) / 2;
		maxLng = (minLng + maxLng) / 2;
	  }
	  else {
		minLat = (minLat + maxLat) / 2;
		minLng = (minLng + maxLng) / 2; }}}function isContains(point, p1, p2) {
	return (point.latitude >= Math.min(p1.latitude, p2.latitude) && point.latitude <= Math.max(p1.latitude, p2.latitude)) && (point.longitude >= Math.min(p1.longitude, p2.longitude) && point.longitude <= Math.max(p1.longitude, p2.longitude));
  }
  
  function transformLatWithXY(x, y) {
	var pi = 3.14159265358979324;
	var lat = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y + 0.2 * Math.sqrt(Math.abs(x));
	lat += (20.0 * Math.sin(6.0 * x * pi) + 20.0 * Math.sin(2.0 * x * pi)) * 2.0 / 3.0;
	lat += (20.0 * Math.sin(y * pi) + 40.0 * Math.sin(y / 3.0 * pi)) * 2.0 / 3.0;
	lat += (160.0 * Math.sin(y / 12.0 * pi) + 320 * Math.sin(y * pi / 30.0)) * 2.0 / 3.0;
	return lat;
  }
  
  function transformLonWithXY(x, y) {
	var pi = 3.14159265358979324;
	var lon = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1 * Math.sqrt(Math.abs(x));
	lon += (20.0 * Math.sin(6.0 * x * pi) + 20.0 * Math.sin(2.0 * x * pi)) * 2.0 / 3.0;
	lon += (20.0 * Math.sin(x * pi) + 40.0 * Math.sin(x / 3.0 * pi)) * 2.0 / 3.0;
	lon += (150.0 * Math.sin(x / 12.0 * pi) + 300.0 * Math.sin(x / 30.0 * pi)) * 2.0 / 3.0;
	return lon;
  }
  
  
  
  module.exports = {
	isLocationOutOfChina: isLocationOutOfChina,
	transformFromWGSToGCJ: transformFromWGSToGCJ,
	transformFromGCJToBaidu: transformFromGCJToBaidu,
	transformFromBaiduToGCJ: transformFromBaiduToGCJ,
	transformFromGCJToWGS: transformFromGCJToWGS
  }
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The original address: blog.csdn.net/lfq88/artic…