Geotagging photos of key outcrops or geoscapes in the field is a very useful thing to do. To geotag a photo is to inscribe the digital file with geographic coordinates. Lots of people are doing it, but I fear that not enough geologists are.
All photo files from digital cameras have an exif header. This stands for 'exchangeable image file format' and it is the area where the file name, date, time, exposure, etc., info is stored. Recent interest in digital mapping has lead to the ability to add specific geographic information (i.e. geographic coordinates) to the exif header. This offers great potential to the field geologist. There are various ways to geo-tag a photograph. Up to now, my preferred way has been to use the free photo-sorting program Picasa (yup, a Google product...more on this at related post) wherein you can manually link a photo to a specific location by dragging it to the map. This works fine in many situations, but can be tedious. Over the last couple of days, I have experimented with a more automatic approach using a program called 'Geosetter' which very efficiently and easily geotags my field photos by directly linking their time-stamp with a corresponding GPS tracklog. Brilliant! In this way, you automatically create a geographically accurate set of field photographs. If you use Google Maps, Picasa, or Google Earth, you can then display the images on a base map of your choice.
Check out an example I made using a Picasa Web Album:
Once at the album, click the 'view map' link. Be sure to zoom way in using the satellite mode to fully appreciate how useful this application is. Furthermore, consider the fact that some of your field photos may be of great value to other geologists, botanists, historians, etc., at some point in time. By tagging them with key words, geo-tagging them, and making them available online, you may be doing a great service to other scientists. Burying them in a paper archive or on a CD somewhere does no good.
Note, you can use Picasa to geotag your photos one-by-one through a link with Google Earth, using a simple drag-and-drop procedure. At some point it is obvious that digital cameras will automatically stamp the file with the coords, but I think the linkage between digital photos and a GPS tracklog may be the best way to go.