EXIF direction (compass) tags

Question

I would like to add the compass bearing/direction to the EXIF metadata of images, however I am quite confused about the many tags in ExifInterface and especially, which formats to use. Could anyone please explain to me for what the different tags are used and especially, in which format the information needs to be added (e.g. 132.00 or 132/100 ,...)?

I have read the documentation online, but I am still confused. Thanks for the help!

ExifInterface.TAG_GPS_IMG_DIRECTION

ExifInterface.TAG_GPS_IMG_DIRECTION_REF

ExifInterface.TAG_GPS_DIRECTION_MAGNETIC

ExifInterface.TAG_GPS_DIRECTION_TRUE

ExifInterface.TAG_GPS_DEST_BEARING

ExifInterface.TAG_GPS_DEST_BEARING_REF

Answer 1

I'm not familiar with ExifInterface but I can tell you the meaning of these tags according to the EXIF standard.

GPS_IMG_DIRECTION is the angle that the image is facing at those coordinates ranging from 0° to 359.99°
GPS_IMG_DIRECTION_REF is whether that direction is based upon True North (set to T) or Magnetic North (set to M)
GPS_DEST_BEARING and GPS_DEST_BEARING_REF are similar, but they detail the direction of travel needed in order to reach the destination (which, if known, would be set in GPSDestLatitude, GPSDestLatitudeRef, GPSDestLongitude, and GPSDestLongitudeRef). This is different from the actual current direction of travel, which is held in the GPSTrack and GPSTrackRef.

I'm not sure what TAG_GPS_DIRECTION_TRUE or TAG_GPS_DIRECTION_MAGNETIC are, as there isn't a matching entry in the EXIF standard as far as I can see. Any directional tag will have a matching reference tag detailing whether the direction is true North or magnetic North.