How to Find Points Within a Radius Using Latitude and Longitude?

Determining Proximity within a Radius Given Latitudes and Longitudes

Envision a scenario where a form allows users to input their longitude and latitude. Simultaneously, a database contains a table housing a comprehensive list of geographic coordinates. The task at hand involves identifying any points within a 15-mile radius of the user's coordinates.

Solution:

To achieve this, we leverage the concept of distance calculation between two points using a specific formula:

function get_distance($latitude1, $longitude1, $latitude2, $longitude2, $unit = 'Mi') {
    $theta = $longitude1 - $longitude2;
    $distance = (sin(deg2rad($latitude1)) * sin(deg2rad($latitude2))) +
                (cos(deg2rad($latitude1)) * cos(deg2rad($latitude2)) *
                cos(deg2rad($theta)));
    $distance = acos($distance);
    $distance = rad2deg($distance);
    $distance = $distance * 60 * 1.1515;
    switch($unit) {
        case 'Mi':
            break;
        case 'Km' :
            $distance = $distance * 1.609344;
    }
    return (round($distance,2));
}

Alternatively, a database query can be utilized:

$query = "SELECT *,(((acos(sin((".$latitude."*pi()/180)) *
            sin((`Latitude`*pi()/180))+cos((".$latitude."*pi()/180)) *
            cos((`Latitude`*pi()/180)) * cos(((".$longitude."- `Longitude`)*
            pi()/180))))*180/pi())*60*1.1515
        ) as distance
        FROM `MyTable`
        HAVING distance >= ".$distance.";

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