You recently discussed point-and-shoot cameras with a built-in GPS receiver but I use a digital SLR. What add-on GPS unit do you recommend for such cameras?
Well Doug, that depends on the brand and model of DSLR. Any camera that employs an SD or MemoryStick Duo series card will work well with a GPS device from Sony, the GPS-CS3KA ($180). And most of the recent mid-range to high-end Nikon DLSRs accept either of three units: Nikon’s GP-1 ($280) and two new models from Easytagger Canada. The latter offers two Easytag models for certain Nikon cameras, a conventional device ($145) and one using Bluetooth technology ($165). (Check the specs for your Nikon DSLR re: compatibility with the GP-1 or check the Easytagger Web site for the availability of a cable for your specific camera.)
The Nikon and Easytagger models automatically add the exact latitude/longitude/altitude for each of photo to the image’s EXIF data folder. You can view the information instantly in Playback mode or later, show it on a map with imaging software or an on-line photo album at a site such as Picasaweb or Panoramio. The Sony GPS-CS3KA requires an extra step. After shooting for some time, insert the SD/SDHC or MemoryStick Duo card from the camera into the external device. Pressing a couple of buttons will cause it to apply the geo-tag data to your image files.
In my tests, the Nikon GP-1 usually acquired location data from satellites in 45 seconds; this unit draws power from the camera’s battery. In preliminary testing, the Easytag GPS modules (which employ a rechargeable built-in battery) were almost as quick. The Sony GPS-CS3KA device (which employs one AA battery) sometimes took several minutes to acquire the location but I did not consider that to be a problem. Note too that all four GPS receivers can continue geo-tagging photos when you go indoors; they simply use the last location data that received from the satellites.
When first acquiring the signals, any type of GPS receiver is most reliable in open areas with a clear view of the sky; the triangulation may not work in a canyon or on a street with tall buildings. All four of the tested models were reliable in most locations and accurate in identifying the latitude/longitude to within 10-20 meters; that’s fine for photo applications. I can recommend any of them for frequent travelers. While location mapping may not be essential, it’s definitely nice to have and it’s a cool extra that your friends will appreciate while viewing your on-line albums.