John’s posterous

One way to accurately synchronize your images with GPS time is to take a picture of the time displayed on your GPS unit while you are out shooting. Then, after you download your images, you can look at this image to get the GPS time and use ExifTool to extract DateTimeOriginal. Say, for example, that the GPS clock reads 19:32:21, DateTimeOriginal is 14:31:49, and your timezone is -05:00. In this case, your camera clock is 32 seconds slow, so you would synchronize your pictures using the following exiftool command:

exiftool -alldates+=00:00:32 C:\Images

(assuming that you downloaded the images to the C:\Images directory). The geotagging will be more accurate after synchronizing the image times like this.

Looks like a really useful tool.