Calculations to get correct EXIF GpsImgDirection depending on Orientation?
I took three photos with the iPhone 3GS, all standing in the same position and all facing east (i.e. 90º). When the button was on the right (Horizontal (normal) orientation), the direction in the EXIF tag (GpsImgDirection) is given as 351/1 or 351.
When the button was on the bottom (portrait or Rotate 90 CW orientation), the direction in the EXIF tag is given as 85/1 or 85. When the button was on the left (Rotate 180 orientation), the direction in the EXIF header is given as 194/1 or 194.
If I'm facing east for all photos, the direction should always be somewhere close to 90. Why not? And is there a calculation that needs to be made taking the orientation into consideration to get the accurate direction? Depending on the camera rotation/orientation, I seem to get a range of N/E/S/W values that don't necessarily correspond to the actual direction, and the calculation is not obvious to me. Any ideas?
When the button was on the bottom (portrait or Rotate 90 CW orientation), the direction in the EXIF tag is given as 85/1 or 85. When the button was on the left (Rotate 180 orientation), the direction in the EXIF header is given as 194/1 or 194.
If I'm facing east for all photos, the direction should always be somewhere close to 90. Why not? And is there a calculation that needs to be made taking the orientation into consideration to get the accurate direction? Depending on the camera rotation/orientation, I seem to get a range of N/E/S/W values that don't necessarily correspond to the actual direction, and the calculation is not obvious to me. Any ideas?
iphone 3Gs, iPhone OS 3.0.1
