PHP code for forward and inverse calculation of longitude and latitude BL and Cartesian coordinates XY

This article mainly introduces the PHP code for forward and inverse calculations of longitude and latitude BL and rectangular coordinates The 54 coordinates of Beijing are divided into 6 degree zones. If you need to use other coordinates, you can modify the parameters $_a, $_f.

Convert latitude and longitude to XY:

<?php
	function BLtoXY($latitude, $longitude)
	{
            $_a = 6378245.0;
        $_f = 1.0 / 298.3;
        $zoneWide = 6;
        $PI = 3.14159265353846;
        $iPI = 0.0174532925199433; //3.1415926535898/180.0; 
        //ZoneWide = 6; //6度带宽 
        $ProjNo = floor($longitude / $zoneWide);
        $longitude0 = $ProjNo * $zoneWide + $zoneWide / 2;
        $longitude0 = $longitude0 * $iPI;
        $latitude0 = 0;
        $longitude1 = $longitude * $iPI; //经度转换为弧度
        $latitude1 = $latitude * $iPI; //纬度转换为弧度
        $e2 = 2 * $_f - $_f * $_f;
        $ee = $e2 * (1.0 - $e2);
        $NN = $_a / sqrt(1.0 - $e2 * sin($latitude1) * sin($latitude1));
        $T = tan($latitude1) * tan($latitude1);
        $C = $ee * cos($latitude1) * cos($latitude1);
        $A = ($longitude1 - $longitude0) * cos($latitude1);
        $M = $_a * ((1 - $e2 / 4 - 3 * $e2 * $e2 / 64 - 5 * $e2 * $e2 * $e2 / 256) * $latitude1 - (3 * $e2 / 8 + 3 * $e2 * $e2 / 32 + 45 * $e2 * $e2 * $e2 / 1024) * sin(2 * $latitude1) + (15 * $e2 * $e2 / 256 + 45 * $e2 * $e2 * $e2 / 1024) * sin(4 * $latitude1) - (35 * $e2 * $e2 * $e2 / 3072) * sin(6 * $latitude1));
        $xval = $NN * ($A + (1 - $T + $C) * $A * $A * $A / 6 + (5 - 18 * $T + $T * $T + 72 * $C - 58 * $ee) * $A * $A * $A * $A * $A / 120);
        $yval = $M + $NN * tan($latitude1) * ($A * $A / 2 + (5 - $T + 9 * $C + 4 * $C * $C) * $A * $A * $A * $A / 24 + (61 - 58 * $T + $T * $T + 600 * $C - 330 * $ee) * $A * $A * $A * $A * $A * $A / 720);
        $X0 = 1000000 * ($ProjNo + 1) + 500000;
        $Y0 = 0;
        $X = round(($xval + $X0) * 100) / 100.0;
            $Y = round(($yval + $Y0) * 100) / 100.0;
		return array($X, $Y);
	}
	$lng = $_GET["lng"];
	$lat = $_GET["lat"];
	$XY = BLtoXY($lat, $lng);
	echo json_encode($XY);
?>

#PHP uses the longitude and latitude between two points to calculate the straight-line distance between two points

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