Geotagging Images

Recently geotagging of images became some popularity due to some articles on popular newspages. I'm already using geotagged images regularly for my work on openstreetmap.

Geotagging images means that you add some metadata in the EXIF-header (part of JPEG-files) where the image was taken. Future cameras probably will include a gps module and will be able to do this automatically, but with today's hardware we need some extra work. Beside manually adding the coordinates, e. g. by clicking on a map, we can synchronize gpx tracks (a common format for recorded gps data) with our images.

I'm usually recording gpx tracks on my mobile phone with Mobile Trail Explorer (a Java/J2ME-software) and an external bluetooth gps device. Before starting, you should accurately set the clock of both devices (the camera and whatever you use to get gpx data). For my hardware I have to do this manually. The mobile phone (Nokia 6230i) supports timesetting via gsm, but my german mobile phone provider doesn't transport that signal. It's also possible to set the time via bluetooth, but then it's rounded down to minutes (at least with gnokii and gammu, I'm not sure if this is an application bug or a hardware limitation), so this is useless, too.
My camera (Canon IXUS 50) seems to have no way of automatically setting the time.

Now, considering you were out somewhere, made some photos while you had another device recording gpx data. There's a small skript called gpsPhoto that will give your images GPS data:

gpsPhoto.pl --dir [directory of your images] --gpsdir [directory of your gpx files] --timeoffset 0

Now you have images that contain data where they were made. JOSM (an openstreetmap tool to create map data) supports showing the geotagged images, which makes editing openstreetmap much easier (you don't have to write down/remember street names, you can take photos of postboxes, bus stops etc. instead of writing down/setting waypoints with your device).

Beside that, this brings up the question if openstreetmap should get a database of geotagged free images together with tools to show them on the map. While this brings up some privacy issues (if the photos contain private buildings, people, car numbers), even the ones without any privacy implications (nature, public buildings) would be a nice feature: Having a map and always being able to say »show me some photos of that location«.
At the moment, this is probably far beyond of the computer ressources available for a project like osm, but it's worth a thought for the future.

Update: Bernd just told me that MTE doesn't use the phone's timestamp, but the one from the GPS device. This means this method doesn't work if your gps doesn't send a correct timestamp signal.