DroneMapper.com: USGS Elevation Web Service PHP Integration

dronemapper_usgselev.php

<?php
/*
 * Uses CURL to return the elevation of a point via USGS Elevation Web Service.
 */
$lat = 41.9816730;
$lon = -106.0949550;

function checkEle($lat, $lon) {
  $ch = curl_init();
  curl_setopt($ch, CURLOPT_URL, "http://gisdata.usgs.gov/xmlwebservices2/elevation_service.asmx/getElevation?X_Value=" . $lon . "&Y_Value=" . $lat . "&Elevation_Units=METERS&Source_Layer=-1&Elevation_Only=true");
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
  curl_setopt($ch, CURLOPT_HEADER, 0);
  $retValue = curl_exec($ch);
  curl_close($ch);
  return $retValue;
}
print checkEle($lat, $lon);
?>