php - How can I calculate distance travelled for a user's journey? -

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in database, have few thousand rows latitude , longitude stores.

in php, how can calculate total distance user has travelled on journey stored in database recorded latitude , longitude points?

is there mathematical equation can reference or something? in system performing calculation on queue , caching user's journey won't change after system has recorded efficiency isn't issue.

i ideally output total of distance travelled in miles.

thanks!

update: here code sample of have done far.

$distance = 0; $earthradius = 6371;  for($i = 0; $i < $journey->data->count(); $i++) {     $currentdata = $journey->data->get($i);     $previousdata = $journey->data->get($i-1);      if($previousdata == null) continue;      $dlat = deg2rad($currentdata->latitude - $previousdata->latitude);     $dlon = deg2rad($currentdata->longitude - $previousdata->longitude);     $a = sin($dlat / 2) * sin($dlat / 2) +           cos(deg2rad($currentdata->latitude)) *           cos(deg2rad($previousdata->latitude)) *           sin($dlon / 2) * sin($dlon / 2);     $c = 2 * atan2(sqrt($a), sqrt(1 - $a));     $distance += $earthradius * $c; }  // $distance should total in kilometers?

is correct?


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