根据经纬度计算距离的公式、百度坐标转换成GPS坐标(PHP版)

 1 <?php
 2 //百度坐标转换成GPS坐标
 3 $lnglat = '121.437518,31.224665';
 4 function FromBaiduToGpsXY($lnglat){
 5 // 经度,纬度
 6 $lnglat = explode(',',$lnglat);
 7 list($x,$y) = $lnglat;
 8 $Baidu_Server = "http://api.map.baidu.com/ag/coord/convert?from=0&to=4&x={$x}&y={$y}";
 9 $result = @file_get_contents($Baidu_Server);
10 $json = json_decode($result);
11 if($json->error == 0)
12 {
13 $bx = base64_decode($json->x);    
14 $by = base64_decode($json->y);
15 $GPS_x = 2 * $x - $bx;
16 $GPS_y = 2 * $y - $by;
17 return $GPS_x.','.$GPS_y;//经度,纬度
18 }
19 else
20 return $lnglat;
21 }
22 /**********************************************/
23 function fn_rad($d)
24 {
25 return $d * pi() / 180.0;
26 }
27 // 2点间算法
28 function P2PDistance($latlng1,$latlng2)
29 {
30 // 纬度1,经度1 ~ 纬度2,经度2
31 $latlng1 = explode(',',$latlng1);
32 $latlng2 = explode(',',$latlng2);
33 list($lat1,$lng1) = $latlng1;
34 list($lat2,$lng2) = $latlng2;
35 $EARTH_RADIUS = 6378.137;
36 $radLat1 = fn_rad($lat1);
37 $radLat2 = fn_rad($lat2);
38 $a = $radLat1 - $radLat2;
39 $b = fn_rad($lng1) - fn_rad($lng2);
40 $s = 2 * asin(sqrt(pow(sin($a/2),2) + cos($radLat1)*cos($radLat2)*pow(sin($b/2),2)));
41 $s = $s * $EARTH_RADIUS;
42 $s = round($s * 10000) / 10000;
43 return number_format($s,2);
44 }
45 echo '百度坐标: ',$lnglat,'<br><br>','转换后GPS坐标: ',FromBaiduToGpsXY($lnglat),'<br><br>';
46 echo '转换前距离: ',P2PDistance('31.224286666667,121.420675','31.224665,121.437518'),'<br/>';
47 echo '转换后距离: ',P2PDistance('31.224286666667,121.420675','31.220157068379,121.42647022694');
48 ?>