wp-gpx-maps/wp-gpx-maps_Utils.php

<?php
	function getPoints($gpxPath,$gpxOffset = 10)
	{
		$points = array();
		$dist=0;
		
		$lastLat=0;
		$lastLon=0;
		$lastEle=0;
		$lastOffset=0;
			
		//Default Offset = 10 mt
		if (!($gpxOffset > 0))
		{
			$gpxOffset = 10;
		}
		
		$realGpxPath = substr (__FILE__, 0, strrpos(__FILE__,'/wp-content/')).$gpxPath;
		
		if (file_exists($realGpxPath))
		{
			
			$gpx = simplexml_load_file($realGpxPath);	
			$gpx->registerXPathNamespace('10', 'http://www.topografix.com/GPX/1/0'); 
			$gpx->registerXPathNamespace('11', 'http://www.topografix.com/GPX/1/1'); 
			
			foreach($gpx->xpath('//trkpt | //10:trkpt | //11:trkpt') as $trkpt){ 
				$lat = $trkpt['lat'];
				$lon = $trkpt['lon'];
				$ele = $trkpt->ele;
				if ($lastLat == 0 && $lastLon == 0)
				{
					//Base Case
					array_push($points, array((float)$lat,(float)$lon,(float)round($ele,1),(float)round($dist,1)));
					$lastLat=$lat;
					$lastLon=$lon;
					$lastEle=$ele;				
				}
				else
				{
					//Normal Case
					$offset = calculateDistance($lat, $lon, $ele,$lastLat, $lastLon, $lastEle);
					$dist = $dist + $offset;
					if (((float) $offset + (float) $lastOffset) > $gpxOffset)
					{
						//Bigger Offset -> write coordinate
						$lastOffset=0;
						array_push($points, array((float)$lat,(float)$lon,(float)round($ele,1),(float)round($dist,1)));
					}
					else
					{
						//Smoller Offset -> continue..
						$lastOffset= (float) $lastOffset + (float) $offset ;
					}
				}
				$lastLat=$lat;
				$lastLon=$lon;
				$lastEle=$ele;
			}
		}
		else
		{
			array_push($points, array((float)0,(float)0,(float)0,(float)0));
		}
		// riduco l'array a circa 200 punti per non appensantire la pagina(mappa e grafico)!
		$count=sizeof($points);
		if ($count>200)
		{
			$f = round($count/200);
			if ($f>1)
				for($i=$count;$i>0;$i--)
					if ($i % $f != 0)
						unset($points[$i]);
		}
		return $points;
	}
	
	function toRadians($degrees)
	{
		return $degrees * 3.1415926535897932385 / 180;
	}	
	
	function calculateDistance($lat1,$lon1,$ele1,$lat2,$lon2,$ele2)
	{
		//Distance in meters
		$dLat = toRadians((float) $lat2 - (float) $lat1);
		$dLng = toRadians((float) $lon2 - (float) $lon1);
		$a = (float) ( sin($dLat / 2) * sin($dLat / 2)) +  (float) ( cos( toRadians($lat1)) * cos( toRadians($lat2)) * sin($dLng / 2) * sin($dLng / 2) );
		$dist = 2 * 3958.75 * atan2(sqrt($a), sqrt(1 - (float) $a));
		return sqrt(pow($dist * 1609.00, 2) + pow((float) $lat1 - (float)$lat2, 2));	
	}
?>