Macworld reviews four geotagging applications for the iPhone. Now the iPhone geotags its own photos — if you take a photo with the iPhone’s built-in camera, it can be automatically geotagged. But these applications turn the iPhone into a GPS logger: you shoot with your regular camera, and merge the time and location data from the iPhone application. A standalone GPS logger is cheaper than an iPhone with two- or three-year data plan, but if you already have an iPhone …