get distance between two coordinates in km

Question

So i'm trying to get the distance between to coordinates using php. I'm using these two functions:

locate user by ip
get image with gps coordinates

in locate user by ip i'm getting the latitude and longitude from the ip, and the putting them in $ lat1 and $ lon1

$ip = $_SERVER['REMOTE_ADDR'];
$details = json_decode(file_get_contents("http://ipinfo.io/{$ip}/json"));
$user_location = $details->loc;
$pieces = explode(",", $user_location);
$lat1 = $pieces[0];
$lon1 = $pieces[1];
$unit = "Km";

in get image i'm selecting the rows, and they all contain the latitude and longitude from the exif.

function get_image($db){
    $select = "id, image_name";
    $sql = "SELECT $select FROM images ORDER BY id DESC";
    $stmt = $db->prepare($sql);
    $stmt->execute();
    $spot = $stmt->fetchAll(PDO::FETCH_ASSOC);

    if(!$stmt -> rowCount()){
        echo "<div class='noSpots'>
                    <p>Sorry there seams to be nothing in your area</p>
              </div>";
    }
        return $spot;
}//spots_narrow ends here

so after these two functions I can now return four variables with the two latitudes and longitudes that i want to calculate the distance between.

- $ lat1
- $ lon1
- $ lat2
- $ lon2

https://developers.google.com/maps/articles/phpsqlsearch_v3 See `Finding Locations with MySQL` — chris85, Sep 25 '15 at 21:27

Jonathan Nazario · Answer 1 · 2015-09-27T03:40:12.360

1

You want to look at the Haversine Formula I'm not keen on PHP, but in pseudo php code this is how it goes:

$EarthRadius = 6371000; // radius in meters
$phi1 = deg2rad($lat1)
$phi2 = deg2rad($lat2)
$deltaLat = deg2rad($lat2 - $lat1)
$deltaLon = deg2rad($lon2 - $lon1)

var $a = sin($deltaLat/2) * sin($deltaLat/2) + cos($phi1) * cos($phi2) * sin($deltaLon / 2) * sin($deltaLon / 2);
var $c = 2 * atan2(sqrt($a), sqrt(1 - $a));

var $result = $EarthRadius * $c;

You should be able to find equivalent formulas for cos, sin, atan2 in PHP Math modules. There are also some other approximations but this should work quite fine.

edited Sep 27 '15 at 03:40

answered Sep 25 '15 at 21:34

Jonathan Nazario

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The above post will give you the distance in meters. – Jonathan Nazario Sep 25 '15 at 21:37
I can't seam to make it work? should i pass the $lat and $lon into $phi1 and $phi2? – user3426191 Sep 25 '15 at 22:06
I was writing pseudo code. Your $lat1 one will be my lat1, $lat2 -> lat2, etc... Also you would use the deg2rad formula to convert to radians. For example: $phi1 = deg2rad($lat1); I will update the post to fix this. – Jonathan Nazario Sep 27 '15 at 03:34

score 0 · Accepted Answer · answered Sep 25 '15 at 21:25

From http://rosettacode.org/wiki/Haversine_formula#PHP

class POI {
    private $latitude;
    private $longitude;
    public function __construct($latitude, $longitude) {
        $this->latitude = deg2rad($latitude);
        $this->longitude = deg2rad($longitude);
    }
    public function getLatitude() return $this->latitude;
    public function getLongitude() return $this->longitude;
    public function getDistanceInMetersTo(POI $other) {
        $radiusOfEarth = 6371000;// Earth's radius in meters.
        $diffLatitude = $other->getLatitude() - $this->latitude;
        $diffLongitude = $other->getLongitude() - $this->longitude;
        $a = sin($diffLatitude / 2) * sin($diffLatitude / 2) +
            cos($this->latitude) * cos($other->getLatitude()) *
            sin($diffLongitude / 2) * sin($diffLongitude / 2);
        $c = 2 * asin(sqrt($a));
        $distance = $radiusOfEarth * $c;
        return $distance;
    }
}

hi how to convert distance into km – Birjitsinh Zala Feb 07 '19 at 05:03 — Birjitsinh Zala, Feb 07 '19 at 05:03

get distance between two coordinates in km

2 Answers2