Getting GPS data from an image’s EXIF in C#

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According to the link posted above by tomfanning, property item 0x0002 is the latitude expressed as a PropertyTagTypeRational. The rational type is defined as…

Specifies that the value data member is an array of pairs of unsigned long integers. Each pair represents a fraction; the first integer is the numerator and the second integer is the denominator.

You are trying to parse it as a string when it’s actually just a series of bytes. According to the above, there should be 3 pairs of 32-bit unsigned integers packed into that byte array, which you can retrieve using the following:

uint degreesNumerator   = BitConverter.ToUInt32(propItem.Value, 0);
uint degreesDenominator = BitConverter.ToUInt32(propItem.Value, 4);
uint minutesNumerator   = BitConverter.ToUInt32(propItem.Value, 8);
uint minutesDenominator = BitConverter.ToUInt32(propItem.Value, 12);
uint secondsNumerator   = BitConverter.ToUInt32(propItem.Value, 16);
uint secondsDenominator = BitConverter.ToUInt32(propItem.Value, 20);

What you do with these values after you’ve got them is for you to work out 🙂 Here’s what the docs say:

Latitude is expressed as three rational values giving the degrees, minutes, and seconds respectively. When degrees, minutes, and seconds are expressed, the format is dd/1, mm/1, ss/1. When degrees and minutes are used and, for example, fractions of minutes are given up to two decimal places, the format is dd/1, mmmm/100, 0/1.

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