Geotagging of photos.

What is geotagging of photos?

Geotagging of photos is inserting geographical metadata in the EXIF-information of a digital pictures. (EXIF-information is hidden data in the digital pictures, which for instance can tell you the make of camera, aperture, shutterspeed and most important the time of the exposure.)

Geotagging can be done manually, but it is far easier to use a GPS-receiver to automatically log positioning data and then use your computer later on to insert this data in the EXIF-information of the photos. This ensures that you can find the place where you took the photos - also after 10 years has passed.

There are two ways to tag photos using a GPS-receiver:

1. The camera has a built-in GPS-receiver or you buy a separate receiver, which is connected to the camera with a cable. This ensures that GPS-data are written in the EXIF-information at the time of exposure, thereby eliminating the necessity of later actions. The downsides are more bulk and the wiring do not look all that solid. Furthermore you may experience a highter battery drain on the camera, if the built-in lightmeter is on at all times or the GPS-receiver is using the cameras battery for power.
   
   
   A Nikon D90 with a GPS-logger mounted in the flash-shoe. No flash while logging GPS-data!
   
   
2. You log GPS-data separately and add the information to EXIF later at your computer. The downsides are that your camera clock must be set accurately, as it is used to combine the data. The logger writes its position every 15-30-60 seconds and saves this to a .txt-file in its memory. If your camera clock is off by one hour for instance, then all your pictures will be positioned wrongly, or no position could be found.

I'm using method 2 and have a Sony GPS-CS1, which is a cheap little GPS-logger. (At the time of writing - January 2009, it can be bought for 295 kr in Kamerahuset on Frederikssundsvej in København/Copenhagen.)


There are probably better GPS-units out there. All units, which can save a tracklog can be utilized. Some units made for car navigation has this functionality, so read the manual of yours.

Here's a link to a review of several units: http://scilib.typepad.com/science_library_pad/2006/09/my_review_of_th.html

The Sony GPS-CS1 is made in three different versions. Sony GPS-CS1, Sony GPS-CS1KA and Sony GPS-CS1KASP. The only diffence is the software which comes with the unit - and as the software is pretty useless, the version of the Sony GPS-CS1 doesn't matter.

Specifications (according to Sony)

• Battery life approx. 10 hours with LR6 ‘AA’ Sony Alkaline battery (I'm getting about 10 hours of battery life using a 2000 mAh re-chargeable cell)
• GPS 12 channel all-in-view tracking, -150 dBm sensitivity, L1 band C/A code (1575.42 MHz) (Not the best chipset, but good enough for my use. It's rarely off by more than 15 meters - 50 feet for those, who still rely on outdated Imperial units)
• Approx. 31 MB memory (This is good for about 360 hours of logging or a month at 10 hours of usage per day. Good for a longer vacation. If you plan on staying away longer than that, you can always empty the unit at an Internet cafe and email the files to yourself.)
• USB 2.0 full speed interface
• Logging every 15. second. (Surely sufficient for photo use. How fast can you run with a heavy camera?)
• Works from 0 to 40° Celsius (Worked great in -30 degrees in China and +35 degrees in Indonesia)
• Size ca. 87mm x 36mm x 36mm
• Weight approx. 55g without battery

When I'm on vacation, I usually turn the unit on in the morning and leave it on all day. I turn it off upon returning to the hotel at night.
When charging the batteries for the camera, I charge the used AA-cell from the GPS-unit and put a fresh one in the unit.
There's a holster and a carabiner in the box, but the carabiner isn't very solid, so I've fixed the holster to the camera strap.

The Sony works like a 31 MB USB-stick on Windows 2000/XP/Vista. It'll pop up as a drive, from where you can copy the .txt-files with positioning data to your harddrive.

It'll name the files based upon the time it was turned on. It uses ISO 8601-format, without punctuations and spaces.
For instance: WG20081225091639.log = 2008-12-25 09.16.39 = Thursday December 25. 2008 - 09.16.39.

When these data are used, you need a computer program to merge the positioning data and the EXIF information. The camera clock is used for this syncronization so it's very important that it is set correctly!

I use Nikon Control to ensure that my camera clock is set correctly before setting out on a trip.

I use the computer program RoboGEO to merge data. http://www.robogeo.com/home/
It's quite user-friendly, yet has many options, which I'll try to describe.
RoboGEO works with most (all?) RAW-formats from different camera makers.

This is an example of how the program actually works.

First you need to define the Time Zone.
GPS data is logged in GMT, and as I prefer to have the camera set to local time, RoboGEO needs to know the time difference.
This is done in "File->Preferences->CommonSettings->UTC Time Bias".



Unfortunately it's less than inituitive that time differences needs to be set in "negative", so my photos from Germany, which is at GMT+1 must be adjusted by -60 minutes.
This function can naturally also be used, if the camera clock was set wrongly.

The photos are added to RoboGEO



The trackfiles are added. "From a NMEA-file." is selected. All the files in the dialog box are selected and added.



Location data is written to the EXIF-header (hidden in the file).



Then you're done and you're free to explore the other options in the program. "Create Googlemap" is selected



You need a Google Map Key, which can be obtained at http://code.google.com/intl/da/apis/base/signup.html

The program does it's thing and the result is as shown:



As you see the red tracklog doesn't follow the roadnet completely. This is because the GPS-receiver was in the trunk of the car, when we drove from one photo position to the next.
Obviously it lost track during this and therefore it connects the "missing" points automatically.

The full result is shown here: http://www.damplokomotiv.dk/TysklandNytaar2009/googlemaps/map.htm

Furthermore I'd like to mention that there's some Freeware alternatives to RoboGEO. They didn't exist, when I purchased RoboGEO, so I've never tried any of them.

The alternatives are Geosetter:

and Microsoft Pro Photo Tools:

Try them out before paying for RoboGEO.

Article written January 2009.

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