Translate Exif DMS to DD Geolocation with Python

I am using the following code to extract the geolocation of an image taken with an iPhone:

from PIL import Image
from PIL.ExifTags import TAGS

def get_exif(fn):
    ret = {}
    i = Image.open(fn)
    info = i._getexif()
    for tag, value in info.items():
        decoded = TAGS.get(tag, tag)
        ret[decoded] = value
    return ret

a = get_exif('photo2.jpg')
print a

This is the result that I am returned:

    {
    'YResolution': (4718592, 65536),
    41986: 0,
    41987: 0,
    41990: 0,
    'Make': 'Apple',
    'Flash': 32,
    'ResolutionUnit': 2,
    'GPSInfo': {
        1: 'N',
        2: ((32, 1), (4571, 100), (0, 1)),
        3: 'W',
        4: ((117, 1), (878, 100), (0, 1)),
        7: ((21, 1), (47, 1), (3712, 100))
    },
    'MeteringMode': 1,
    'XResolution': (4718592, 65536),
    'ExposureProgram': 2,
    'ColorSpace': 1,
    'Exi开发者_如何学运维fImageWidth': 1600,
    'DateTimeDigitized': '2011:03:01 13:47:39',
    'ApertureValue': (4281, 1441),
    316: 'Mac OS X 10.6.6',
    'SensingMethod': 2,
    'FNumber': (14, 5),
    'DateTimeOriginal': '2011:03:01 13:47:39',
    'ComponentsConfiguration': '\x01\x02\x03\x00',
    'ExifOffset': 254,
    'ExifImageHeight': 1200,
    'Model': 'iPhone 3G',
    'DateTime': '2011:03:03 10:37:32',
    'Software': 'QuickTime 7.6.6',
    'Orientation': 1,
    'FlashPixVersion': '0100',
    'YCbCrPositioning': 1,
    'ExifVersion': '0220'
}

So, I am wondering how I convert the GPSInfo values (DMS) to Decimal Degrees for actual coordinates? Also, there seems to be two Wests listed . . . ?

Here's a way to do it, adapted for a script I wrote some months ago using pyexiv2:

a = get_exif('photo2.jpg')
lat = [float(x)/float(y) for x, y in a['GPSInfo'][2]]
latref = a['GPSInfo'][1]
lon = [float(x)/float(y) for x, y in a['GPSInfo'][4]]
lonref = a['GPSInfo'][3]

lat = lat[0] + lat[1]/60 + lat[2]/3600
lon = lon[0] + lon[1]/60 + lon[2]/3600
if latref == 'S':
    lat = -lat
if lonref == 'W':
    lon = -lon

This gives me the following latitude and longitude for your picture: 32.7618333, -117.146333 (same results as Lance Lee).

The last entry of GPSInfo may be the heading of the picture. You could check this using a tool that gives proper names to the different EXIF values such as exiv2 or exiftools.

http://www.exiv2.org/tags.html find the string 'Exif.GPSInfo.GPSLatitude' in that page. It appears that you get 3 pairs (representing rationals) and the second number in the pair is the denominator. I would expect the thing after Longitude to be altitude, however it is a better fit for GPS timestamp.

In this example:

32/1 + (4571 / 100)/60 + (0 / 1)/3600 = 32.761833 N
117/1 + (878 / 100)/60 + (0 / 1)/3600 = 117.146333 W

Was this picture taken near 4646 Park Blvd, San Diego, CA 92116? If not then ignore this answer.