SOFTWARE - [Photo GPS Extract]- [About Geotagging]

About Geotagging

How can a picture have a GPS location?

By default, a picture doesn't contain GPS data. You need to have a GPS - enabled camera. This is a camera with an integrated GPS module. Each time you make a photo, the geographic location is added to the photo.

Only a small amount of cameras have a build-in GPS module. There are a few solutions to overcome this problem:

In some cases you can buy an add-on GPS receiver for your camera. It is a little piece of hardware you can connect to your camera with a cable. Of course your camera must support such GPS receiver. Very few does.
Another solution is to add the GPS data to the pictures by hand. You can use programs like Google Picasa for this. In short: you can assign a GPS location to any photo by selecting a location in Google Earth.
The third option is to carry a portable GPS with logging capabilities while taking pictures. Later you can read the logged route from your GPS, and use a third-party software to merge this information into your photos. This is my preferred way to geotag photos, and I will explain this in detail later on.

Merging GPS data into photos using RoboGEO

As I just explained it is my preferred way to Geotag my photos by using an external GPS device. I have bought myself the Garmin Oregon 450t for this reason. It is a portable GPS unit, powered by 2 AA batteries. This unit has many options to save the tracks you have walked. The tracks are stored as files with the .GPX extension (GPS eXchange Format). My tracks usually have an logging interval of 10 seconds. This means the GPS location is recorded every 10 seconds.

You can download the track logs by connecting the GPS device to your computer. Now you have a track logfile on your computer, you can start merging the GPS information into your pictures. I use the commercial RoboGEO software [External] tool to do this:

Open the RoboGEO software.
Import your pictures into RoboGEO (File > Get Images > Entire Folder).
Import your track log into RoboGEO (File > Get Locations > Track Log > Import Track Log File)
Now RoboGEO will try to find the GPS location for each picture.
When RoboGEO is done you have to write the GPS location into the .JPG files (File > Process > Write Exif Headers)

You are done! Now all of your pictures will contain the GPS location.

You might be wondering how RoboGEO can link a picture with a location. First of all you should be aware that each photo contains the date & time of its creation. RoboGEO will read this information from all of your selected .JPG files. Then it will search the .GPX track log to see where you were at each of these times.