GPSLatitude

[gch]

Hi,
I'm playing with exiftool (thanks for this awesome tool!!) for a while and read some EXIF documentation (http://www.exiftool.org/TagNames/EXIF.html), I'm coding a little tool, and I'm in a front of something...

I'm trying to understand how exiftool can compute this value :

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GPS Latitude                    : 0 deg 23' 58.91" S


The "S", I get it.
"0 deg 23'", I get it to.
but what about the 58.91" value ?

I explain : using the command below :

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$ exiftool -v3 IMG_8394.CR2 | grep -A5 -i "gps"


The concerned values are :

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| | 1)  GPSLatitudeRef = S
| |     - Tag 0x0001 (2 bytes, string[2]):
| |        11072: 53 00                                           [S.]      <-- the famous "S" value, no problem here.
| | 2)  GPSLatitude = 0 23.9818 0 (0/1 239818/10000 0/1)
| |     - Tag 0x0002 (24 bytes, rational64u[3]):
| |        111d6: 00 00 00 00 01 00 00 00 ca a8 03 00 10 27 00 00 [.............'..]
| |        111e6: 00 00 00 00 01 00 00 00                         [........]
[...]


In 2)
the first 8 bytes 00 00 00 00 01 00 00 00 represent 0/1
the second 8 bytes ca a8 03 00 10 27 00 00 represent 239818/10000, so 23.9818...
the third 8 bytes 00 00 00 00 01 00 00 00 represent 0/1

So I totally understand the results "GPSLatitude = 0 23.9818 0 (0/1 239818/10000 0/1)" returned by the commande exiftool -v3.

But I don't find a way to get how we can compute the last part : "58.91".

Someone could explain this to me ? It will be really appreciated.

Another question, but not so important, just curiosity:
The below command :

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$exiftool -htmlDump img.CR2 > output.html

display those values (0/1 239818/10000 0/1) and not "0 deg 23' 58.91" S", it's this the normal behavior ? I'm using exiftool 9.76 under MacOSX.

.

[Phil Harvey]

By default, ExifTool reports coordinates in degrees, minutes, and seconds, but this may be changed with the -c or -n options.

If this doesn't answer your question, please let me know.

- Phil

[gch]

Well, that didn't answer my question, but I've figured it out.
Thanks anyway =)

In my previous sample :

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| | 1)  GPSLatitudeRef = S
| |     - Tag 0x0001 (2 bytes, string[2]):
| |        11072: 53 00
| | 2)  GPSLatitude = 0 23.9818 0 (0/1 239818/10000 0/1)
| |     - Tag 0x0002 (24 bytes, rational64u[3]):
| |        111d6: 00 00 00 00 01 00 00 00 ca a8 03 00 10 27 00 00 [.............'..]
| |        111e6: 00 00 00 00 01 00 00 00                         [........]


Where:

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d = 00 00 00 00 01 00 00 00 = 0/1 = 0
m = ca a8 03 00 10 27 00 00 = 239818/10000 = 23.9818
s = 00 00 00 00 01 00 00 00 = 0/1 = 0


By applying the formula http://en.wikipedia.org/wiki/Geographic_coordinate_conversion

The final result is 0 deg 23' 58.91" S.