Index: includes/Exif.php
===================================================================
--- includes/Exif.php	(revision 61759)
+++ includes/Exif.php	(working copy)
@@ -255,13 +255,13 @@
 			'gps' => array(
 				'GPSVersionID' => Exif::BYTE,			# GPS tag version
 				'GPSLatitudeRef' => Exif::ASCII,		# North or South Latitude #p52-53
-				'GPSLatitude' => Exif::RATIONAL,		# Latitude
+				'GPSLatitude' => Exif::RATIONAL,		# Latitude (special workaround handling)
 				'GPSLongitudeRef' => Exif::ASCII,		# East or West Longitude #p53
-				'GPSLongitude' => Exif::RATIONAL,		# Longitude
-				'GPSAltitudeRef' => Exif::BYTE,		# Altitude reference
+				'GPSLongitude' => Exif::RATIONAL,		# Longitude (special workaround handling)
+				'GPSAltitudeRef' => Exif::BYTE,			# Altitude reference
 				'GPSAltitude' => Exif::RATIONAL,		# Altitude
 				'GPSTimeStamp' => Exif::RATIONAL,		# GPS time (atomic clock)
-				'GPSSatellites' => Exif::ASCII,		# Satellites used for measurement
+				'GPSSatellites' => Exif::ASCII,			# Satellites used for measurement
 				'GPSStatus' => Exif::ASCII,			# Receiver status #p54
 				'GPSMeasureMode' => Exif::ASCII,		# Measurement mode #p54-55
 				'GPSDOP' => Exif::RATIONAL,			# Measurement precision
@@ -273,16 +273,16 @@
 				'GPSImgDirection' => Exif::RATIONAL,		# Direction of image
 				'GPSMapDatum' => Exif::ASCII,			# Geodetic survey data used
 				'GPSDestLatitudeRef' => Exif::ASCII,		# Reference for latitude of destination #p56
-				'GPSDestLatitude' => Exif::RATIONAL,		# Latitude destination
+				'GPSDestLatitude' => Exif::RATIONAL,		# Latitude destination (special workaround handling)
 				'GPSDestLongitudeRef' => Exif::ASCII,		# Reference for longitude of destination #p57
-				'GPSDestLongitude' => Exif::RATIONAL,		# Longitude of destination
+				'GPSDestLongitude' => Exif::RATIONAL,		# Longitude of destination (special workaround handling)
 				'GPSDestBearingRef' => Exif::ASCII,		# Reference for bearing of destination #p57
 				'GPSDestBearing' => Exif::RATIONAL,		# Bearing of destination
 				'GPSDestDistanceRef' => Exif::ASCII,		# Reference for distance to destination #p57-58
 				'GPSDestDistance' => Exif::RATIONAL,		# Distance to destination
 				'GPSProcessingMethod' => Exif::UNDEFINED,	# Name of GPS processing method
 				'GPSAreaInformation' => Exif::UNDEFINED,	# Name of GPS area
-				'GPSDateStamp' => Exif::ASCII,		# GPS date
+				'GPSDateStamp' => Exif::ASCII,			# GPS date
 				'GPSDifferential' => Exif::SHORT,		# GPS differential correction
 			),
 		);
@@ -348,6 +348,39 @@
 			}
 		}
 
+		// Work around a bug in the definitions above: GPS coordinates may be arrays of degree-minutes-seconds
+		// If we find such a coordinate, we convert it here to single a fractional degree.
+		//   This work-around fixes bug 13172 without changing the metadata format at all. (But leaves the
+		// other fields in the metadata that also should be arrays untouched.)
+		foreach( array( 'GPSLatitude' => 90, 'GPSLongitude' => 180, 'GPSDestLatitude' => 90, 'GPSDestLongitude' => 180) as $gpsTag => $max) {
+			if( !array_key_exists( $gpsTag, $this->mFilteredExifData ) ) continue;
+			$data = $this->mFilteredExifData[$gpsTag];
+			if( !is_array( $data ) ) continue;
+			$val = 0;
+			$divisor = 1;
+			foreach( $data as $v ) {
+				$m = array();
+				if( !preg_match( '/^(\d+)\/(\d+)$/', $v, $m ) || $m[2] == 0 ) break;
+				$val += ( $m[1] / $m[2] ) / $divisor;
+				$divisor *= 60;
+				if( $divisor > 3600 ) break;
+			}
+			if( $val <= 0.0 ) {
+				$num = 0; $denom = 1;
+			} else {
+				// 7 digits is more than enough. It corresponds to an accuracy of about 1cm,
+				// which is more than the current GPS systems can deliver in terms of
+				// precision. Even if more precise locations should appear in the future
+				// in EXIF data, 1cm is surely precise enough to pinpoint a photographer's
+				// location.
+				$val = round( $val, 7 );
+				if ( $val > $max ) $val = $max;
+				$denom = 10000000; // 10**7
+				$num = intval( $val * $denom );
+			}
+			$this->mFilteredExifData[$gpsTag] = $num . "/" . $denom;
+		}
+		
 		foreach( $this->mFilteredExifData as $k => $v ) {
 			if ( !$this->validate($k, $v) ) {
 				$this->debug( $v, __FUNCTION__, "'$k' contained invalid data" );
@@ -613,6 +646,14 @@
 	var $mExif;
 
 	/**
+	 * Values for the geolocation coordinate references
+	 *
+	 * @var array
+	 * @private
+	 */
+	var $mGeoReferences;
+	
+	/**
 	 * Constructor
 	 *
 	 * @param $exif Array: the Exif data to format ( as returned by
@@ -620,6 +661,13 @@
 	 */
 	function FormatExif( $exif ) {
 		$this->mExif = $exif;
+		$this->mGeoReferences = array(
+			 'GPSLatitudeRef' => null
+			,'GPSLongitudeRef' => null
+			,'GPSDestLatitudeRef' => null
+			,'GPSDestLongitudeRef' => null
+			,'GPSAltitudeRef' => 0 // Default: above sea level
+		);
 	}
 
 	/**
@@ -638,6 +686,11 @@
 		$resolutionunit = !isset( $tags['ResolutionUnit'] ) || $tags['ResolutionUnit'] == 2 ? 2 : 3;
 		unset( $tags['ResolutionUnit'] );
 
+		foreach( $this->mGeoReferences as $gpsRefTag => $value) {
+			if( !array_key_exists( $gpsRefTag, $tags ) ) continue;
+			$this->mGeoReferences[$gpsRefTag] = $tags[$gpsRefTag];
+		}
+		
 		foreach( $tags as $tag => $val ) {
 			switch( $tag ) {
 			case 'Compression':
@@ -967,6 +1020,28 @@
 				}
 				break;
 
+			case 'GPSLatitude':
+			case 'GPSDestLatitude':
+			case 'GPSLongitude':
+			case 'GPSDestLongitude':
+				$tags[$tag] = $this->formatCoordinate( $val, $this->mGeoReferences[$tag . 'Ref'] );
+				break;
+
+			case 'GPSAltitudeRef':
+				switch( $val ) {
+				case 0: case 1:
+					$tags[$tag] = $this->msg( 'GPSAltitude', $val );
+					break;
+				default:
+					$tags[$tag] = $val;
+					break;
+				}
+				break;
+				
+			case 'GPSAltitude' :
+				$tags[$tag] = $this->msg( 'GPSAltitudeValue', $this->mGeoReferences[$tag . 'Ref'], $this->formatNum ( $val ) );
+				break;
+				
 			case 'GPSStatus':
 				switch( $val ) {
 				case 'A': case 'V':
@@ -990,7 +1065,6 @@
 				break;
 
 			case 'GPSSpeedRef':
-			case 'GPSDestDistanceRef':
 				switch( $val ) {
 				case 'K': case 'M': case 'N':
 					$tags[$tag] = $this->msg( 'GPSSpeed', $val );
@@ -1001,6 +1075,17 @@
 				}
 				break;
 
+			case 'GPSDestDistanceRef':
+				switch( $val ) {
+				case 'K': case 'M': case 'N':
+					$tags[$tag] = $this->msg( 'GPSDestDistance', $val );
+					break;
+				default:
+					$tags[$tag] = $val;
+					break;
+				}
+				break;
+
 			case 'GPSTrackRef':
 			case 'GPSImgDirectionRef':
 			case 'GPSDestBearingRef':
@@ -1120,6 +1205,39 @@
 	}
 
 	/**
+	 * Format a coordinate value.
+	 *
+	 * @param $num Mixed: coordinate value in degrees
+	 * @param $direction String (optional): 'N', 'S', 'E', or 'W'
+	 * @return String: coordinate value in degrees, minutes and seconds
+	 * @private
+	 */
+	function formatCoordinate( $num, $direction=null ) {
+		global $wgContLang;
+		
+		$m = array();
+		if ( is_numeric( $num ) ) {
+			$den = 1;  // we use fmod() below so that $num can be a float too
+			$fnum = $this->formatNum( round ( $num, 7 ) );
+		} else if ( preg_match( '/^(\d+)\/(\d+)$/', $num, $m ) && $m[2] != 0 ) {
+			$num = $m[1]; $den = $m[2];
+			$fnum = $this->formatNum( round ( $num / $den , 7 ) );
+		} else {
+			return $this->formatNum( $num );
+		}
+		$deg = intval( $num / $den );
+		$num = 60 * fmod( $num, $den );
+		$min = intval( $num / $den );
+		$num = 60 * fmod( $num, $den );
+		// Limit seconds to at most 3 fractional digits: that's already in the
+		// millimeter range!
+		$sec = $this->formatNum( round ( $num / $den , 3 ) );
+		$tag = 'exif-coordinate-format';
+		if ( $direction != null ) $tag .= '-' . $wgContLang->lc( $direction );
+		return wfMsg( $tag, $deg, $min, $sec, $fnum );
+	}
+
+	/**
 	 * Calculate the greatest common divisor of two integers.
 	 *
 	 * @param $a Integer: FIXME
@@ -1145,6 +1263,7 @@
 		}
 		return $a;
 	}
+
 }
 
 /**
Index: languages/messages/MessagesEn.php
===================================================================
--- languages/messages/MessagesEn.php	(revision 61756)
+++ languages/messages/MessagesEn.php	(working copy)
@@ -3674,6 +3674,13 @@
 'exif-gpsdatestamp'                => 'GPS date',
 'exif-gpsdifferential'             => 'GPS differential correction',
 
+# Coordinate value in deg/min/sec, used for GPS location data. $4 is same in decimal degrees.
+'exif-coordinate-format'           => '$1° $2\' $3"',
+'exif-coordinate-format-n'         => '$1° $2\' $3" N',
+'exif-coordinate-format-s'         => '$1° $2\' $3" S',
+'exif-coordinate-format-e'         => '$1° $2\' $3" E',
+'exif-coordinate-format-w'         => '$1° $2\' $3" W',
+
 # Make & model, can be wikified in order to link to the camera and model name
 'exif-make-value'     => '$1', # do not translate or duplicate this message to other languages
 'exif-model-value'    => '$1', # do not translate or duplicate this message to other languages
@@ -3840,6 +3847,19 @@
 'exif-gpsspeed-m' => 'Miles per hour',
 'exif-gpsspeed-n' => 'Knots',
 
+# Pseudotags used for GPSDestDistanceRef
+'exif-gpsdestdistance-k' => 'Kilometers',
+'exif-gpsdestdistance-m' => 'Miles',
+'exif-gpsdestdistance-n' => 'Nautical miles',
+
+# Pseudotags used for GPSAltitudeRef
+'exif-gpsaltitude-0' => 'Meters above sea level',
+'exif-gpsaltitude-1' => 'Meters below sea level',
+
+# Pseudotags used for GPSAltitudeRef
+'exif-gpsaltitudevalue-0' => '+ $1 m',
+'exif-gpsaltitudevalue-1' => '- $1 m',
+
 # Pseudotags used for GPSTrackRef, GPSImgDirectionRef and GPSDestBearingRef
 'exif-gpsdirection-t' => 'True direction',
 'exif-gpsdirection-m' => 'Magnetic direction',