My side of the camera

Hi friends!

After a very long time, here comes an english written post again

This time it's about image geotagging, that means providing digital photos with their exact coordinates where they were taken.

If you don't have a bleeding edge camera, most probably your cam won't have a GPS device in it and cannot do that itself. I use a Pentax K10D, which is rather modern, but not bleeding edge at all, so I faced this problem. So it's about recording the track of your trip and providing the coords to the pics afterwards on the PC.

Logically, this means, you need to carry another device around with you, that can record your track using GPS. In my case it's a HTC Hero, an Android based cell phone with a GPS chip built in. I used the free Android App "My Tracks" to record the whole trip through the garden and court of the Castillo in Heidelberg, Germany. I set the software to log as many trackpoints as possible, which is about one point per second. I set it to skip points where the precision is lower than 20 meters. Then I clipped the phone to the top of my bag pack and let it just run throughout my trip. At the end I saved the resulting track to my SD card in GPX format, which contains not just the position, but additionally height, speed and even walking direction (because my phone has an electronic compass).

At home I searched for good solutions to bring the data together and ended with a Windows software named GPS-Track-Analyze.NET. I imported the whole track which had lots of points, around 1200. The software had no problems importing that. It then showed me the 2D and even a 3D height profile of my track, and it can even calculate estimated consumption of calories and stuff Quite funny I have to admit

The software now can look through the folder where I placed the images of the trip and then it compares the timestamp of the picture with the nearest trackpoint my phone recorded at the very same second. As you might figure, timing is a problem here. In an environment like a castle garden or such, withing 2 minutes you have reached a whole other place. That's why you can enter a time difference in the GPS Track Analyzer. You just have to know the difference. I used the simple trick to open the clock on my phone and took a picture of that clock. Then on the PC I compared the image timestamp with the time the phone clock showed and came to the result, that the difference was 4 mins and 27 seconds. That's what I set in the GPS Track Analyzer then. By default, GPS Track Analyzer combines all pictures within 500m to one matching trackpoint. But I wanted to have exact coords in the images, so I set this down to 5m and let it match the data. Worked quite well!

I then chose to write the coords of the matching trackpoint into the EXIF tags of the images. That worked as well, too, but then it automatically wanted to reload the pictures and crashed. I could reproduce that a few times, so better save your track before you plan to do that.

Voila, done! All pictures have GPS coordinates in their EXIF tags

I now went further:

You can export a track into google earth kmz format, containing the images as scaled down thumbs and optional with a link to the full image. In this track I wanted to have image waypoints for the images. I wanted to combine all images in a 10m range into one waypoint, so I set the range like we did above and let it match the track again. Then I created all the image waypoints. That's easy, you select all images and select "create image waypoints" and set some options to your liking, like waypoint naming scheme.

Then I realized, that 1200 trackpoints are really over the top and chose to reduce them. GPS Track Analyzer has some very advanced functions to do that, and I chose the default which looked quite right to me and the result was satisfying. Trackpoint count went down to about 400 and the track was still good looking.

Export to Google Earth kmz, including thumbs and links to the images on my local hard disk, all straight-forward. You can also upload the images to any webspace and let the export function link those images then. You can then give out the kmz file as a geo image album to friends.
Update: I should add that the program will freeze for quite some time while exporting the kmz with included image thumbnails. You need patience, it's not crashed.

You can now open the resultin kmz file in Google Earth and you can look at your track and the images and can see where exactly you took them.

I hope you liked that rough overview and perhaps some of you have the change and devices to try that out. It's real fun!

Best,
Daniel