diff --git a/android/src/main/java/com/lodev09/exify/ExifyModule.kt b/android/src/main/java/com/lodev09/exify/ExifyModule.kt
index f6fbe8d..6d8fb86 100644
--- a/android/src/main/java/com/lodev09/exify/ExifyModule.kt
+++ b/android/src/main/java/com/lodev09/exify/ExifyModule.kt
@@ -42,7 +42,7 @@ class ExifyModule(
     // On Android Q+, request ACCESS_MEDIA_LOCATION for unredacted GPS data
     if (scheme == "content" && Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q &&
       ContextCompat.checkSelfPermission(context, Manifest.permission.ACCESS_MEDIA_LOCATION) !=
-        PackageManager.PERMISSION_GRANTED
+      PackageManager.PERMISSION_GRANTED
     ) {
       val activity = context.currentActivity as? PermissionAwareActivity
       if (activity != null) {
@@ -156,14 +156,46 @@ class ExifyModule(
           tags.hasKey(ExifInterface.TAG_GPS_LATITUDE) &&
           tags.hasKey(ExifInterface.TAG_GPS_LONGITUDE)
         ) {
-          exif.setLatLong(
-            tags.getDouble(ExifInterface.TAG_GPS_LATITUDE),
-            tags.getDouble(ExifInterface.TAG_GPS_LONGITUDE),
-          )
+          val hasExplicitRef =
+            tags.hasKey(ExifInterface.TAG_GPS_LATITUDE_REF) ||
+              tags.hasKey(ExifInterface.TAG_GPS_LONGITUDE_REF)
+
+          if (hasExplicitRef) {
+            val lat = tags.getDouble(ExifInterface.TAG_GPS_LATITUDE)
+            val lng = tags.getDouble(ExifInterface.TAG_GPS_LONGITUDE)
+            val latRef =
+              if (tags.hasKey(ExifInterface.TAG_GPS_LATITUDE_REF)) {
+                tags.getString(ExifInterface.TAG_GPS_LATITUDE_REF)
+              } else {
+                if (lat >= 0) "N" else "S"
+              }
+            val lngRef =
+              if (tags.hasKey(ExifInterface.TAG_GPS_LONGITUDE_REF)) {
+                tags.getString(ExifInterface.TAG_GPS_LONGITUDE_REF)
+              } else {
+                if (lng >= 0) "E" else "W"
+              }
+
+            exif.setAttribute(ExifInterface.TAG_GPS_LATITUDE, ExifyUtils.decimalToDms(Math.abs(lat)))
+            exif.setAttribute(ExifInterface.TAG_GPS_LATITUDE_REF, latRef)
+            exif.setAttribute(ExifInterface.TAG_GPS_LONGITUDE, ExifyUtils.decimalToDms(Math.abs(lng)))
+            exif.setAttribute(ExifInterface.TAG_GPS_LONGITUDE_REF, lngRef)
+          } else {
+            exif.setLatLong(
+              tags.getDouble(ExifInterface.TAG_GPS_LATITUDE),
+              tags.getDouble(ExifInterface.TAG_GPS_LONGITUDE),
+            )
+          }
         }
 
         if (tags.hasKey(ExifInterface.TAG_GPS_ALTITUDE)) {
-          exif.setAltitude(tags.getDouble(ExifInterface.TAG_GPS_ALTITUDE))
+          val alt = tags.getDouble(ExifInterface.TAG_GPS_ALTITUDE)
+          if (tags.hasKey(ExifInterface.TAG_GPS_ALTITUDE_REF)) {
+            exif.setAttribute(ExifInterface.TAG_GPS_ALTITUDE, ExifyUtils.decimalToRational(Math.abs(alt)))
+            exif.setAttribute(ExifInterface.TAG_GPS_ALTITUDE_REF, tags.getInt(ExifInterface.TAG_GPS_ALTITUDE_REF).toString())
+          } else {
+            exif.setAltitude(alt)
+          }
         }
 
         params.putString("uri", uri)
diff --git a/android/src/main/java/com/lodev09/exify/ExifyUtils.kt b/android/src/main/java/com/lodev09/exify/ExifyUtils.kt
index 3e331ee..6421bd1 100644
--- a/android/src/main/java/com/lodev09/exify/ExifyUtils.kt
+++ b/android/src/main/java/com/lodev09/exify/ExifyUtils.kt
@@ -46,4 +46,19 @@ object ExifyUtils {
 
     return tags
   }
+
+  @JvmStatic
+  fun decimalToDms(decimal: Double): String {
+    val degrees = decimal.toInt()
+    val minutesDecimal = (decimal - degrees) * 60
+    val minutes = minutesDecimal.toInt()
+    val seconds = ((minutesDecimal - minutes) * 60 * 10000).toLong()
+    return "$degrees/1,$minutes/1,$seconds/10000"
+  }
+
+  @JvmStatic
+  fun decimalToRational(value: Double): String {
+    val numerator = (value * 10000).toLong()
+    return "$numerator/10000"
+  }
 }
diff --git a/example/src/App.tsx b/example/src/App.tsx
index 46d1d6c..f8a54d6 100644
--- a/example/src/App.tsx
+++ b/example/src/App.tsx
@@ -40,8 +40,10 @@ export default function App() {
   const writeExif = async (uri: string) => {
     const [lng, lat] = mockPosition();
     const tags: ExifTags = {
-      GPSLatitude: lat,
-      GPSLongitude: lng,
+      GPSLatitude: Math.abs(lat),
+      GPSLatitudeRef: lat >= 0 ? 'N' : 'S',
+      GPSLongitude: Math.abs(lng),
+      GPSLongitudeRef: lng >= 0 ? 'E' : 'W',
       GPSTimeStamp: '10:10:10',
       GPSDateStamp: '2024:10:10',
       GPSDOP: 5.0,
@@ -61,6 +63,18 @@ export default function App() {
     return result;
   };
 
+  const readWriteRoundTrip = async (uri: string) => {
+    const tags = await Exify.read(uri);
+    if (!tags) return;
+
+    console.log('roundTrip read:', json(tags));
+    const result = await Exify.write(uri, tags);
+    console.log('roundTrip write:', json(result));
+
+    const verify = await Exify.read(uri);
+    console.log('roundTrip verify:', json(verify));
+  };
+
   const takePhoto = async () => {
     if (!cameraRef.current) return;
 
@@ -79,27 +93,42 @@ export default function App() {
     await readExif(asset.uri);
   };
 
-  const openLibrary = async () => {
+  const pickImage = async () => {
     const result = await ImagePicker.launchImageLibraryAsync({
       mediaTypes: ['images'],
       quality: 1,
     });
 
-    if (result.canceled) return;
+    if (result.canceled) return null;
 
     const asset = result.assets[0];
-    if (!asset) return;
+    if (!asset) return null;
 
     const uri =
       Platform.OS === 'ios' && asset.assetId
         ? `ph://${asset.assetId}`
         : asset.uri;
 
-    console.log('openLibrary:', uri);
     setPreview(asset.uri);
+    return uri;
+  };
+
+  const openLibrary = async () => {
+    const uri = await pickImage();
+    if (!uri) return;
+
+    console.log('openLibrary:', uri);
     await readExif(uri);
   };
 
+  const testRoundTrip = async () => {
+    const uri = await pickImage();
+    if (!uri) return;
+
+    console.log('testRoundTrip:', uri);
+    await readWriteRoundTrip(uri);
+  };
+
   const openUrl = async () => {
     const defaultUrl =
       'https://raw.githubusercontent.com/ianare/exif-samples/master/jpg/gps/DSCN0010.jpg';
@@ -139,7 +168,11 @@ export default function App() {
       <CameraView ref={cameraRef} style={styles.camera} facing="back" />
       <PromptSheet ref={promptRef} />
       <View style={styles.controls}>
-        <Pressable onPress={openLibrary} style={styles.previewButton}>
+        <Pressable
+          onPress={openLibrary}
+          onLongPress={testRoundTrip}
+          style={styles.sideButton}
+        >
           {preview && (
             <Image source={{ uri: preview }} style={styles.preview} />
           )}
@@ -147,7 +180,7 @@ export default function App() {
         <Pressable onPress={takePhoto} style={styles.captureButton}>
           <View style={styles.captureInner} />
         </Pressable>
-        <Pressable onPress={openUrl} style={styles.urlButton}>
+        <Pressable onPress={openUrl} style={styles.sideButton}>
           <Text style={styles.urlLabel}>URL</Text>
         </Pressable>
       </View>
@@ -180,11 +213,15 @@ const styles = StyleSheet.create({
     backgroundColor: '#000',
     width: '100%',
   },
-  previewButton: {
+  sideButton: {
     width: 50,
     height: 50,
     borderRadius: 8,
     backgroundColor: '#333',
+    borderWidth: 1,
+    borderColor: '#555',
+    alignItems: 'center',
+    justifyContent: 'center',
     overflow: 'hidden',
   },
   preview: {
@@ -206,14 +243,6 @@ const styles = StyleSheet.create({
     borderRadius: 29,
     backgroundColor: '#fff',
   },
-  urlButton: {
-    width: 50,
-    height: 50,
-    borderRadius: 8,
-    backgroundColor: '#333',
-    alignItems: 'center',
-    justifyContent: 'center',
-  },
   urlLabel: {
     color: '#fff',
     fontSize: 13,
diff --git a/ios/Exify.mm b/ios/Exify.mm
index ee850ad..dbfc4e7 100644
--- a/ios/Exify.mm
+++ b/ios/Exify.mm
@@ -3,14 +3,13 @@
 static NSSet *tiffKeys;
 
 __attribute__((constructor)) static void initTiffKeys(void) {
-  tiffKeys = [NSSet setWithObjects:@"Make", @"Model", @"Software", @"DateTime",
-                                   @"Artist", @"Copyright", @"ImageDescription",
-                                   @"Orientation", @"XResolution",
-                                   @"YResolution", @"ResolutionUnit",
-                                   @"Compression", @"PhotometricInterpretation",
-                                   @"TransferFunction", @"WhitePoint",
-                                   @"PrimaryChromaticities", @"HostComputer",
-                                   nil];
+  tiffKeys = [NSSet
+      setWithObjects:@"Make", @"Model", @"Software", @"DateTime", @"Artist",
+                     @"Copyright", @"ImageDescription", @"Orientation",
+                     @"XResolution", @"YResolution", @"ResolutionUnit",
+                     @"Compression", @"PhotometricInterpretation",
+                     @"TransferFunction", @"WhitePoint",
+                     @"PrimaryChromaticities", @"HostComputer", nil];
 }
 
 #pragma mark - Helpers
@@ -122,6 +121,11 @@ static void addTagEntries(CFStringRef dictionary, NSDictionary *metadata,
                                             kCGImagePropertyGPSDictionary]
                                    ?: @{}];
 
+  // Pre-read explicit GPS ref values so coordinate handlers can use them
+  NSString *latRef = tags[@"GPSLatitudeRef"];
+  NSString *lngRef = tags[@"GPSLongitudeRef"];
+  NSNumber *altRef = tags[@"GPSAltitudeRef"];
+
   for (NSString *key in tags) {
     id value = tags[key];
 
@@ -129,18 +133,21 @@ static void addTagEntries(CFStringRef dictionary, NSDictionary *metadata,
       double lat = [value doubleValue];
       gpsDict[(__bridge NSString *)kCGImagePropertyGPSLatitude] = @(fabs(lat));
       gpsDict[(__bridge NSString *)kCGImagePropertyGPSLatitudeRef] =
-          lat >= 0 ? @"N" : @"S";
+          latRef ?: (lat >= 0 ? @"N" : @"S");
     } else if ([key isEqualToString:@"GPSLongitude"]) {
       double lng = [value doubleValue];
-      gpsDict[(__bridge NSString *)kCGImagePropertyGPSLongitude] =
-          @(fabs(lng));
+      gpsDict[(__bridge NSString *)kCGImagePropertyGPSLongitude] = @(fabs(lng));
       gpsDict[(__bridge NSString *)kCGImagePropertyGPSLongitudeRef] =
-          lng >= 0 ? @"E" : @"W";
+          lngRef ?: (lng >= 0 ? @"E" : @"W");
     } else if ([key isEqualToString:@"GPSAltitude"]) {
       double alt = [value doubleValue];
       gpsDict[(__bridge NSString *)kCGImagePropertyGPSAltitude] = @(fabs(alt));
       gpsDict[(__bridge NSString *)kCGImagePropertyGPSAltitudeRef] =
-          @(alt >= 0 ? 0 : 1);
+          altRef ?: @(alt >= 0 ? 0 : 1);
+    } else if ([key isEqualToString:@"GPSLatitudeRef"] ||
+               [key isEqualToString:@"GPSLongitudeRef"] ||
+               [key isEqualToString:@"GPSAltitudeRef"]) {
+      // Already handled above
     } else if ([key hasPrefix:@"GPS"]) {
       gpsDict[[key substringFromIndex:3]] = value;
     } else if ([tiffKeys containsObject:key]) {