GPX interleave

gistfile1.php

<?php

$inputFile = 'file.gpx';
$start = '2015-01-24 08:46:05';
$speed = '19';



function dist(
    $latitudeFrom, $longitudeFrom, $latitudeTo, $longitudeTo, $earthRadius = 6371000) {

      // convert from degrees to radians
      $latFrom = deg2rad($latitudeFrom);
      $lonFrom = deg2rad($longitudeFrom);
      $latTo = deg2rad($latitudeTo);
      $lonTo = deg2rad($longitudeTo);

      $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;
}

$gps = file_get_contents($inputFile);
$start = @strtotime($start);
$speed = $speed / 3.6; // m/s

$last = false;
foreach (preg_split("#\s*\n\s*#", $gps) as $line) {
    $regs = array();
    if (preg_match('#<trkpt\s*lat="(.*?)"\s*lon="(.*?)"/>#', $line, $regs)) {

        if ($lastLat) {
            $dist = dist($lastLat, $lastLon, $regs[1], $regs[2]);
            $diff = $dist / ($speed * rand(8,12) / 10);
            $start += round($diff);
            echo "<trkpt lat=\"$regs[1]\" lon=\"$regs[2]\"><time>".@date('c', $start)."</time></trkpt>";
        } else {
            echo $regs[0];
        }
        $lastLat = $regs[1];
        $lastLon = $regs[2];
        echo "\n";
    }
}