I love geo-tagging!
Taking a picture means to freeze a moment of your life, be it just a funny detail you noticed walking in the street, or a breathtaking sunset behind a mountain. And by geo-tagging your pictures you add some piece of information to your memories, the exact (in some meters' precision) position in the world, and the exact time and date when it was taken. This can come handy not only to globe-trotters wandering all over the world, or to people who tends to forgot places they visited.
A geo-tagged picture, declined with internet social philosophy, means showing where you took those pictures to everyone in the planet who views your photogallery on the internet. Take a look here to see what you can get. Isn't it sweet?
Some top class digital cameras offer geo-tagging features: each time you take a shoot, an internal GPS device records current position, and stores it on the picture's JPG file. How is it stored? JPG files have a peculiar place to store a lot of informations in addition to the pure image, the EXIF header. Interesting informations like shutter, exposition time, use of flash and so on are stored on EXIF. As well, GPS position can be stored on EXIF. This way you can keep all those extra informations easily along with the image itself. Some photo browser programs like Picasa allow you to see those images informations, if available.
Now, how do you get to share the joy of geo-tagging if you don't own those top class digital cameras with GPS feature? You have two choices: either you geo-tag manually your pictures with software like Google Earth, with all the boredom and slowness this process implies; or, if you own a Pocket PC with a GPS receiver, some programs will do the trick for you automatically with a little effort.
Here is how to do it: when you go out to take photos with your camera, take your Pocket PC too. Make sure to place it away from sensible objects like magnetic credit cards or bus tickets, because GPS receiver can demagnetize them easily. I usually put it on an empty pocket on my jacket (a chest pocket is better because it will be more exposed to sky, hence to satellites' signal), or in a little bag I take with me.
The Pocket PC will continuously records GPS informations with any free program like VisualGPS. These informations contains - amongst others - latitude, longitude and exact GMT date and time. All you need to do is to start the program, enable logging to a file (make sure you have some free storage space) and forget about GPS! No, you don't need to get to the Pocket PC each time you take a photo. Just start it and forget it!
You can now take as many photos as you want, and when you have finished, just make sure to stop your GPS logger program before shutting off the Pocket PC, so your log file won't get corrupted.
When you go back home, download your pictures to your computer, and the GPS log file from your Pocket PC. Then download and launch this fantastic software, PhotoMapper by Copiks. From the file menu, you can import images and GPS data. If you can't find the GPS log files on the directory, it could be that the Pocket PC program saved the file with a different extension than those expected by PhotoMapper. For example, VisualGPS usually saves them as .txt files. But don't worry, just rename the file to a .log extension so the program will load it.
What happens next? The program will look at the time you took each picture, and will be able to tell where the picture was taken merging informations with the GPS log file. That is because the GPS receiver tracks continuously (even more frequently than a second) position informations (latitude, longitude) and time. In fact, the program shows the satellite view map of the area where you took the pictures and the path you walked. And, for pictures that have been taken while the GPS logger was working, will place a small point in the path showing where the picture was taken. For each picture, you will get following informations: filename, datetime, latitude, longitude, altitude. There is another column, named "adjusted time". That's because you might need to adjust time difference between camera's internal clock and GPS clock (most probably much more in time than your camera's clock, as it comes from satellites!). In fact a difference between these two times might result in a misplace of the picture - before or after its true shooting place, following the GPS path. Assuming you walk straight from a point to the other, if your camera's clock is one minute late compared to correct time (GPS' time), the program will place the photos in the place where you were one minute later after you actually shot them. Or, for example, you just couldn't have set up camera's clock with new daylight saving offset! In those cases, you can adjust shooting times using the time adjustment controls under the pictures list. Set it as fast or low if camera's clock was late or early, and the amount of correction. And then you're done! For each picture geo-placed you will find the position informations marked in red. Now you can select the images (you can select them all clicking over the first column on the left, just like on an Excel sheet), and click on the "tag selected images" button: doing so, your pictures will be geo-tagged! Now if you look at the images with Picasa, a little cross in the lower right corner of the thumbnails will tell the picture is geo-referenced: from "tools" menu you will be able to show image's place on Google Earth. In addition, if you upload your pictures to Picasaweb, Picasa's free image hosting service, you will be able to show the map where the pictures were taken.
If you don't want to use Picasa, from Copiks' PhotoMapper you can click on "export to Google Earth" button, and you'll see your pictures and your path directly on Google Earth! You can save the KML file for loading your GPS path and your pictures to Google Earth directly later on.
I have been testing this geo-tagging method for a year and I'm very happy with it. The weakest part of the process is keeping the camera's clock in time with GPS' clock. To smooth this part, I developed a little tool for Pocket PC that displays GPS' current time. This can help in two ways: either to adjust camera's time before a photo-taking session, or, if you don't want to lose time with this, just take a picture of the Pocket PC running the application showing GPS time; later, loading the picture in Copiks' PhotoMapper, you will see GPS time in the picture and camera time on the grid so you will be able to adjust perfectly the time offset.
This tool is called GPSTime, you can download it here. I hope you will find it useful!
Enjoy geotagging!
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