diff --git a/lib/adapters/GPX.class.php b/lib/adapters/GPX.class.php
index 4a3cdb1e..139f1706 100644
--- a/lib/adapters/GPX.class.php
+++ b/lib/adapters/GPX.class.php
@@ -32,7 +32,7 @@ public function read($gpx) {
    * @return string The KML string representation of the input geometries
    */
   public function write(Geometry $geometry) {
-    return $this->geometryToGPX($geometry);
+    return '<gpx creator="geoPHP" version="1.0">'.$this->geometryToGPX($geometry).'</gpx>';
   }
   
   public function geomFromText($text) {
diff --git a/lib/adapters/KML.class.php b/lib/adapters/KML.class.php
index 63b19bdb..e4e1c9e1 100644
--- a/lib/adapters/KML.class.php
+++ b/lib/adapters/KML.class.php
@@ -71,16 +71,26 @@ protected function geomFromXML() {
     $geometries = array();
     $geom_types = geoPHP::geometryList();
     $placemark_elements = $this->xmlobj->getElementsByTagName('placemark');
-    foreach ($placemark_elements as $placemark) {
-      foreach ($placemark->childNodes as $child) {
-        // Node names are all the same, except for MultiGeometry, which maps to GeometryCollection
-        $node_name = $child->nodeName == 'multigeometry' ? 'geometrycollection' : $child->nodeName;
-        if (array_key_exists($node_name, $geom_types)) {
-          $function = 'parse'.$geom_types[$node_name];
-          $geometries[] = $this->$function($child);
+    if ($placemark_elements->length) {
+      foreach ($placemark_elements as $placemark) {
+        foreach ($placemark->childNodes as $child) {
+          // Node names are all the same, except for MultiGeometry, which maps to GeometryCollection
+          $node_name = $child->nodeName == 'multigeometry' ? 'geometrycollection' : $child->nodeName;
+          if (array_key_exists($node_name, $geom_types)) {
+            $function = 'parse'.$geom_types[$node_name];
+            $geometries[] = $this->$function($child);
+          }
         }
       }
     }
+    else {
+      // The document does not have a placemark, try to create a valid geometry from the root element
+      $node_name = $this->xmlobj->documentElement->nodeName == 'multigeometry' ? 'geometrycollection' : $this->xmlobj->documentElement->nodeName;
+      if (array_key_exists($node_name, $geom_types)) {
+        $function = 'parse'.$geom_types[$node_name];
+        $geometries[] = $this->$function($this->xmlobj->documentElement);
+      }
+    }
     return geoPHP::geometryReduce($geometries); 
   }
   
@@ -188,8 +198,11 @@ private function pointToKML($geom) {
     return "<Point><coordinates>".$geom->getX().",".$geom->getY()."</coordinates></Point>";
   }
 
-  private function linestringToKML($geom) {
-    $type = $geom->getGeomType();
+  private function linestringToKML($geom, $type = FALSE) {
+    if (!$type) {
+      $type = $geom->getGeomType();
+    }
+    
     $str = '<'. $type .'><coordinates>';
     $i=0;
     foreach ($geom->getComponents() as $comp) {
@@ -203,7 +216,7 @@ private function linestringToKML($geom) {
 
   public function polygonToKML($geom) {
     $components = $geom->getComponents();
-    $str = '<outerBoundaryIs>' . $this->linestringToKML($components[0]) . '</outerBoundaryIs>';
+    $str = '<outerBoundaryIs>' . $this->linestringToKML($components[0], 'LinearRing') . '</outerBoundaryIs>';
     foreach (array_slice($components, 1) as $comp) {
       $str .= '<innerBoundaryIs>' . $this->linestringToKML($comp) . '</innerBoundaryIs>';
     }
diff --git a/lib/geometry/Geometry.class.php b/lib/geometry/Geometry.class.php
index 679140b5..6d48756d 100644
--- a/lib/geometry/Geometry.class.php
+++ b/lib/geometry/Geometry.class.php
@@ -71,12 +71,13 @@ public function envelope() {
     
     $bbox = $this->getBBox();
     $points = array (
-      new Point($bbox['maxy'],$bbox['minx']),
-      new Point($bbox['maxy'],$bbox['maxx']),
-      new Point($bbox['miny'],$bbox['maxx']),
-      new Point($bbox['miny'],$bbox['minx']),
-      new Point($bbox['maxy'],$bbox['minx']),
+      new Point($bbox['maxx'],$bbox['miny']),
+      new Point($bbox['maxx'],$bbox['maxy']),
+      new Point($bbox['minx'],$bbox['maxy']),
+      new Point($bbox['minx'],$bbox['miny']),
+      new Point($bbox['maxx'],$bbox['miny']),
     );
+    
     $outer_boundary = new LineString($points);
     return new Polygon(array($outer_boundary));
   }
@@ -85,7 +86,6 @@ public function geometryType() {
     return $this->geom_type;
   }
   
-  
   // Public: Non-Standard -- Common to all geometries
   // ------------------------------------------------
   public function getGeoInterface() {
diff --git a/lib/geometry/Polygon.class.php b/lib/geometry/Polygon.class.php
index dbe45bf0..49a4a4ff 100644
--- a/lib/geometry/Polygon.class.php
+++ b/lib/geometry/Polygon.class.php
@@ -88,8 +88,8 @@ public function centroid() {
       $cn['y'] = $cn['y'] + ($p->getY() + $pts[$j]->getY()) * $P;
     }
     
-    $cn['x'] = - $cn['x'] / ( 6 * $a);
-    $cn['y'] = - $cn['y'] / ( 6 * $a);
+    $cn['x'] = $cn['x'] / ( 6 * $a);
+    $cn['y'] = $cn['y'] / ( 6 * $a);
         
     $centroid = new Point($cn['x'], $cn['y']);
     return $centroid;
diff --git a/tests/test.php b/tests/test.php
index 9496bb88..f00c814a 100644
--- a/tests/test.php
+++ b/tests/test.php
@@ -2,6 +2,13 @@
 
 include_once('../geoPHP.inc');
 
+if (geoPHP::geosInstalled()) {
+  print "GEOS is installed. ";
+}
+else {
+  print "GEOS is not installed. ";
+}
+
 foreach (scandir('./input') as $file) {
   $parts = explode('.',$file);
   if ($parts[0]) {
@@ -12,16 +19,7 @@
   }
 }
 
-function test_geometry($geometry) {
-  // Test adapter output
-  $geometry->out('wkt');
-  $geometry->out('wkb');
-  $geometry->out('kml');
-  $geometry->out('gpx');
-  $geometry->out('json');
-  
-  //Don't test google geocoder regularily. Uncomment to test
-  #$geometry->out('google_geocode');  
+function test_geometry($geometry, $test_adapters = TRUE) {
   
   // Test common functions
   $geometry->area();
@@ -98,6 +96,19 @@ function test_geometry($geometry) {
   $geometry->coordinateDimension();
   $geometry->z();
   $geometry->m();
+
+  // Test adapter output and input. Do a round-trip and re-test
+  if ($test_adapters) {
+    foreach (geoPHP::getAdapterMap() as $adapter_key => $adapter_class) {
+      if ($adapter != 'google_geocode') { //Don't test google geocoder regularily. Uncomment to test
+        $format = $geometry->out($adapter_key);
+        $adapter_loader = new $adapter_class();
+        $translated_geometry = $adapter_loader->read($format);
+        #test_geometry($translated_geometry, FALSE);
+      }
+    }
+  }
+  
 }
 
 print "Done! Test passes!";
\ No newline at end of file