根据经纬度计算距离的公式、百度坐标转换成GPS坐标(PHP版)
<?php//百度坐标转换成GPS坐标$lnglat = '121.437518,31.224665';function FromBaiduToGpsXY($lnglat){// 经度,纬度$lnglat = explode(',',$lnglat);list($x,$y) = $lnglat;$Baidu_Server = "http://api.map.baidu.com/ag/coord/convert?from=0&to=4&x={$x}&y={$y}";$result = @file_get_contents($Baidu_Server);$json = json_decode($result);if($json->error == 0){$bx = base64_decode($json->x);$by = base64_decode($json->y);$GPS_x = 2 * $x - $bx;$GPS_y = 2 * $y - $by;return $GPS_x.','.$GPS_y;//经度,纬度} else return $lnglat;}/**********************************************/function fn_rad($d){return $d * pi() / 180.0;}// 2点间算法function P2PDistance($latlng1,$latlng2){// 纬度1,经度1 ~ 纬度2,经度2$latlng1 = explode(',',$latlng1);$latlng2 = explode(',',$latlng2);list($lat1,$lng1) = $latlng1;list($lat2,$lng2) = $latlng2;$EARTH_RADIUS = 6378.137;$radLat1 = fn_rad($lat1);$radLat2 = fn_rad($lat2);$a = $radLat1 - $radLat2; $b = fn_rad($lng1) - fn_rad($lng2);$s = 2 * asin(sqrt(pow(sin($a/2),2) + cos($radLat1)*cos($radLat2)*pow(sin($b/2),2)));$s = $s * $EARTH_RADIUS;$s = round($s * 10000) / 10000;return number_format($s,2);}echo '百度坐标: ',$lnglat,'<br><br>','转换后GPS坐标: ',FromBaiduToGpsXY($lnglat),'<br><br>';echo '转换前距离: ',P2PDistance('31.224286666667,121.420675','31.224665,121.437518'),'<br/>';echo '转换后距离: ',P2PDistance('31.224286666667,121.420675','31.220157068379,121.42647022694');?>