diff --git a/Photo.cs b/Photo.cs
index e6e6ab1..258e2a9 100644
--- a/Photo.cs
+++ b/Photo.cs
@@ -9,6 +9,88 @@ using System.Xml.Linq;
 
 namespace SemiColinGames;
 
+// https://exiftool.org/TagNames/GPS.html
+public struct GpsInfo {
+  public byte[] VersionId;
+  public string Status;
+  public string Datestamp;
+  public Rational[] Timestamp;
+  public Rational[] Latitude;
+  public string LatitudeRef;
+  public Rational[] Longitude;
+  public string LongitudeRef;
+  public Rational Altitude;
+  public byte AltitudeRef;
+
+  // GpsStatus? DateStamp and TimeStamp?
+  public static GpsInfo? ParseExif(ExifProfile exif) {
+    GpsInfo gps;
+
+    IExifValue<byte[]>? versionId;
+    IExifValue<string>? status;
+    IExifValue<string>? datestamp;
+    IExifValue<Rational[]>? timestamp;
+    IExifValue<Rational[]>? latitude;
+    IExifValue<string>? latitudeRef;
+    IExifValue<Rational[]>? longitude;
+    IExifValue<string>? longitudeRef;
+    IExifValue<Rational>? altitude;
+    IExifValue<byte>? altitudeRef;
+
+    if (!exif.TryGetValue(ExifTag.GPSVersionID, out versionId)) {
+      return null;
+    }
+    gps.VersionId = versionId.Value ?? throw new NullReferenceException();
+
+    if (!exif.TryGetValue(ExifTag.GPSStatus, out status)) {
+      return null;
+    }
+    gps.Status = status.Value ?? throw new NullReferenceException();
+
+    if (!exif.TryGetValue(ExifTag.GPSDateStamp, out datestamp)) {
+      return null;
+    }
+    gps.Datestamp = datestamp.Value ?? throw new NullReferenceException();
+
+    if (!exif.TryGetValue(ExifTag.GPSTimestamp, out timestamp)) {
+      return null;
+    }
+    gps.Timestamp = timestamp.Value ?? throw new NullReferenceException();
+
+    if (!exif.TryGetValue(ExifTag.GPSLatitude, out latitude)) {
+      return null;
+    }
+    gps.Latitude = latitude.Value ?? throw new NullReferenceException();
+
+    if (!exif.TryGetValue(ExifTag.GPSLatitudeRef, out latitudeRef)) {
+      return null;
+    }
+    gps.LatitudeRef = latitudeRef.Value ?? throw new NullReferenceException();
+
+    if (!exif.TryGetValue(ExifTag.GPSLongitude, out longitude)) {
+      return null;
+    }
+    gps.Longitude = longitude.Value ?? throw new NullReferenceException();
+
+    if (!exif.TryGetValue(ExifTag.GPSLongitudeRef, out longitudeRef)) {
+      return null;
+    }
+    gps.LongitudeRef = longitudeRef.Value ?? throw new NullReferenceException();
+
+    if (!exif.TryGetValue(ExifTag.GPSAltitude, out altitude)) {
+      return null;
+    }
+    gps.Altitude = altitude.Value;
+
+    if (!exif.TryGetValue(ExifTag.GPSAltitudeRef, out altitudeRef)) {
+      return null;
+    }
+    gps.AltitudeRef = altitudeRef.Value;
+
+    return gps;
+  }
+}
+
 public class Photo {
   public string Filename;
   public bool Loaded = false;
@@ -24,8 +106,7 @@ public class Photo {
   public string IsoSpeed = "<unk>";
   public int Rating = 0;
   public ushort Orientation = 1;
-  public Rational[]? GpsLatitude = null;
-  public Rational[]? GpsLongitude = null;
+  public GpsInfo? Gps = null;
   public Rectangle CropRectangle = Rectangle.Empty;
 
   private static long touchCounter = 0;
@@ -93,7 +174,6 @@ public class Photo {
     string filename = System.IO.Path.Combine(directory, System.IO.Path.GetFileName(Filename));
     Console.WriteLine("saving " + filename);
     // FIXME: add comments / captions as ImageDescription?
-    // FIXME: strip some Exif tags for privacy reasons?
     // FIXME: warn if the file already exists?
     using (Image<Rgba32> image = await Image.LoadAsync<Rgba32>(Filename)) {
       Util.RotateImageFromExif(image, Orientation);
@@ -112,8 +192,20 @@ public class Photo {
         "{0:D4}:{1:D2}:{2:D2} {3:D2}:{4:D2}:{5:D2}",
         now.Year, now.Month, now.Day, now.Hour, now.Minute, now.Second);
       exif.SetValue<string>(ExifTag.DateTime, datetime);
-      exif.SetValue<Rational[]>(ExifTag.GPSLatitude, GpsLatitude);
-      exif.SetValue<Rational[]>(ExifTag.GPSLongitude, GpsLongitude);
+
+      if (Gps != null) {
+        GpsInfo gps = (GpsInfo) Gps;
+        exif.SetValue<byte[]>(ExifTag.GPSVersionID, gps.VersionId);
+        exif.SetValue<string>(ExifTag.GPSStatus, gps.Status);
+        exif.SetValue<string>(ExifTag.GPSDateStamp, gps.Datestamp);
+        exif.SetValue<Rational[]>(ExifTag.GPSTimestamp, gps.Timestamp);
+        exif.SetValue<Rational[]>(ExifTag.GPSLatitude, gps.Latitude);
+        exif.SetValue<string>(ExifTag.GPSLatitudeRef, gps.LatitudeRef);
+        exif.SetValue<Rational[]>(ExifTag.GPSLongitude, gps.Longitude);
+        exif.SetValue<string>(ExifTag.GPSLongitudeRef, gps.LongitudeRef);
+        exif.SetValue<Rational>(ExifTag.GPSAltitude, gps.Altitude);
+        exif.SetValue<byte>(ExifTag.GPSAltitudeRef, gps.AltitudeRef);
+      }
 
       image.Metadata.XmpProfile = UpdateXmp(image.Metadata.XmpProfile);
 
@@ -272,15 +364,7 @@ public class Photo {
       }
     }
 
-    IExifValue<Rational[]>? gpsLatitude;
-    if (exifs.TryGetValue(ExifTag.GPSLatitude, out gpsLatitude)) {
-      GpsLatitude = gpsLatitude.Value;
-    }
-
-    IExifValue<Rational[]>? gpsLongitude;
-    if (exifs.TryGetValue(ExifTag.GPSLongitude, out gpsLongitude)) {
-      GpsLongitude = gpsLongitude.Value;
-    }
+    Gps = GpsInfo.ParseExif(exifs);
   }
 
   public string GetShortLensModel(string lensModel) {
diff --git a/Program.cs b/Program.cs
index d027409..be8ca54 100644
--- a/Program.cs
+++ b/Program.cs
@@ -386,8 +386,8 @@ public class Game : GameWindow {
     geometry = new UiGeometry(nwSettings.Size, STAR_FILLED.Size.X);
   }
 
-  private static string outputRoot = @"c:\users\colin\desktop\totte-output";
-  // private static string outputRoot = @"c:\users\colin\pictures\photos";
+  // private static string outputRoot = @"c:\users\colin\desktop\totte-output";
+  private static string outputRoot = @"c:\users\colin\pictures\photos";
 
   private static Texture TEXTURE_WHITE = new(new Image<Rgba32>(1, 1, new Rgba32(255, 255, 255)));
   private static Texture TEXTURE_BLACK = new(new Image<Rgba32>(1, 1, new Rgba32(0, 0, 0)));
@@ -687,8 +687,8 @@ public class Game : GameWindow {
     // string[] files = Directory.GetFiles(@"c:\users\colin\desktop\photos-test\");
     // string[] files = Directory.GetFiles(@"c:\users\colin\pictures\photos\2023\07\14\");
     // string[] files = Directory.GetFiles(@"c:\users\colin\pictures\photos\2023\07\23\");
-    string[] files = Directory.GetFiles(@"G:\DCIM\100EOSR6\");
-    // string[] files = Directory.GetFiles(@"c:\users\colin\desktop\totte-output\2023\07\31");
+    // string[] files = Directory.GetFiles(@"G:\DCIM\100EOSR6\");
+    string[] files = Directory.GetFiles(@"c:\users\colin\desktop\totte-output\2023\08\29");
     // string[] files = Directory.GetFiles(@"c:\users\colin\desktop\import");
     // string[] files = Directory.GetFiles(@"C:\Users\colin\Pictures\photos\2018\06\23");
     // string[] files = Directory.GetFiles(@"C:\Users\colin\Desktop\Germany all\104D7000");
@@ -705,17 +705,15 @@ public class Game : GameWindow {
     allPhotos.Sort(ComparePhotosByDate);
 
     // Fix up photos with missing GPS.
-    Rational[]? lastLatitude = null;
-    Rational[]? lastLongitude = null;
+    GpsInfo? lastGps = null;
     foreach (Photo p in allPhotos) {
-      if (p.GpsLatitude != null && p.GpsLongitude != null) {
-        lastLatitude = p.GpsLatitude;
-        lastLongitude = p.GpsLongitude;
+      if (p.Gps != null) {
+        lastGps = p.Gps;
       }
-      if (p.GpsLatitude == null || p.GpsLongitude == null) {
+      if (p.Gps == null) {
+        // FIXME: should we take from the photo immediately _before_, or after?
         Console.WriteLine("fixing GPS for " + p.Filename);
-        p.GpsLatitude = lastLatitude;
-        p.GpsLongitude = lastLongitude;
+        p.Gps = lastGps;
       }
     }
     photos = allPhotos;