guint64 metadata_read_int(FileData *fd, const gchar *key, guint64 fallback);
gdouble metadata_read_GPS_coord(FileData *fd, const gchar *key, gdouble fallback);
gdouble metadata_read_GPS_direction(FileData *fd, const gchar *key, gdouble fallback);
+gboolean metadata_write_GPS_coord(FileData *fd, const gchar *key, gdouble value);
gboolean metadata_append_string(FileData *fd, const gchar *key, const char *value);
gboolean metadata_append_list(FileData *fd, const gchar *key, const GList *values);