Geo Location functions

Geo.php

<?php

namespace Acme\Component\Utils;

class Geo
{
    const EARTH_RADIUS = 3959; // in miles

    /**
     * Given a $centre (latitude, longitude) co-ordinates and a
     * distance $radius (miles), returns a random point (latitude,longtitude)
     * which is within $radius meters of $centre.
     *
     * @param $latitude
     * @param $longitude
     * @param float $radius The radius (in meters).
     *
     * @return array
     */
    public static function generateRandomPoint($latitude, $longitude, $radius)
    {
        $centre = array($latitude, $longitude);
        $radius_earth = self::EARTH_RADIUS * 1609.344; // in meters

        // Pick random distance within $distance;
        $distance = lcg_value() * $radius;

        // Convert degrees to radians.
        $centre_rads = array_map('deg2rad', $centre);

        // First suppose our point is the north pole.
        // Find a random point $distance miles away
        $lat_rads = (pi() / 2) - $distance / $radius_earth;
        $lng_rads = lcg_value() * 2 * pi();

        // ($lat_rads,$lng_rads) is a point on the circle which is
        // $distance miles from the north pole. Convert to Cartesian
        $x1 = cos($lat_rads) * sin($lng_rads);
        $y1 = cos($lat_rads) * cos($lng_rads);
        $z1 = sin($lat_rads);

        // Rotate that sphere so that the north pole is now at $centre.

        // Rotate in x axis by $rot = (pi()/2) - $centre_rads[0];
        $rot = (pi() / 2) - $centre_rads[0];
        $x2 = $x1;
        $y2 = $y1 * cos($rot) + $z1 * sin($rot);
        $z2 = -$y1 * sin($rot) + $z1 * cos($rot);

        //Rotate in z axis by $rot = $centre_rads[1]
        $rot = $centre_rads[1];
        $x3 = $x2 * cos($rot) + $y2 * sin($rot);
        $y3 = -$x2 * sin($rot) + $y2 * cos($rot);
        $z3 = $z2;

        //Finally convert this point to polar co-ords
        $lng_rads = atan2($x3, $y3);
        $lat_rads = asin($z3);

        $return = array_map('rad2deg', array($lat_rads, $lng_rads));
        return array('latitude' => $return[0], 'longitude' => $return[1]);
    }

    /**
     * Return the boundaries of a square around a geo point according the specified distance
     *
     * @param $latitude
     * @param $longitude
     * @param int $distance
     * @return array
     */
    public static function getGeoBoundaries($latitude, $longitude, $distance=2000)
    {
        // earth's radius in km = ~6371
        $radius = self::EARTH_RADIUS * 1609.344;
        $return = array(
            'ref_lat' => $latitude,
            'ref_lng' => $longitude,
            'distance' => $distance,
            'max_lat' => null,
            'min_lat' => null,
            'max_lng' => null,
            'min_lng' => null,
        );

        // latitude boundaries
        $return['max_lat'] = $latitude + rad2deg($distance / $radius);
        $return['min_lat'] = $latitude - rad2deg($distance / $radius);

        // longitude boundaries (longitude gets smaller when latitude increases)
        $return['max_lng'] = $longitude + rad2deg($distance / $radius / cos(deg2rad($latitude)));
        $return['min_lng'] = $longitude - rad2deg($distance / $radius / cos(deg2rad($latitude)));

        return $return;
    }

    /**
     * Return the great-circle distance in meters between 2 geo points using the Vincenty formula (more precise)
     *
     * @param float $lat1
     * @param float $lng1
     * @param float $lat2
     * @param float $lng2
     *
     * @return float distance in meters
     */
    public static function distance($lat1, $lng1, $lat2, $lng2)
    {
        $earthRadius = self::EARTH_RADIUS * 1609.344;

        // convert from degrees to radians
        $latFrom = deg2rad($lat1);
        $lonFrom = deg2rad($lng1);
        $latTo = deg2rad($lat2);
        $lonTo = deg2rad($lng2);

        $lonDelta = $lonTo - $lonFrom;
        $a = pow(cos($latTo) * sin($lonDelta), 2) +
            pow(cos($latFrom) * sin($latTo) - sin($latFrom) * cos($latTo) * cos($lonDelta), 2);
        $b = sin($latFrom) * sin($latTo) + cos($latFrom) * cos($latTo) * cos($lonDelta);

        $angle = atan2(sqrt($a), $b);
        return $angle * $earthRadius;
    }
}