Nice picture, where was it taken? The more photos I accumulate, the less often I can say for certain. When I first heard about photo-geotagging, I thought it was a neat idea, if for no other reason than to reduce the number of lame excuses I’d have to give for not remembering.

Within the EXIF (Exchangeable Image File Format) portion of each digital image file is a wealth of information including tags to identify location. Few cameras natively exploit the location tags, but you can fill them with the correct location information after the fact. The early solutions were somewhat homebrew — if you had a handheld GPS unit, you could take it with you to record location data, then use special software and a PC or Mac to add the correct GPS data to each photo.

Then I learned that some higher-end Nikon SLRs can write GPS data directly to a JPEG or even a NEF RAW file. You still need a handheld GPS unit plus a special Nikon MC-35 cable that connects to the camera’s communications port, but no post-processing is required because the location is recorded in the camera original.

A Hong Kong based company called Dawn Technology Ltd. (www.dawntech.hk) has a more refined solution called the di-GPS. This GPS unit was originally designed only for the Nikons that had GPS support, but recently the company added a USB model that is compatible with higher-end Canon SLRs. The USB model requires the cameras be equipped with Canon’s WFT-E3 or WFT-E2 (depending on the camera model) wireless transmitter module, however.

The unit I purchased in late February was a second-generation model for Nikon cameras, and that’s the unit on which this report is based. It cost just over $300 including shipping, but the company has since come up with two third-generation models for Nikon (in addition to the USB model for Canon) that are somewhat less expensive. Compared to a handheld GPS unit plus MC-35 cable, the di-GPS advances usability in three ways. First, it is much smaller than your typical hobbyist GPS unit. Second, it has a shoe mount so it attaches directly to the camera’s hot shoe (you can also attach it to a camera strap). Third, the short cable attaches directly to the camera’s MC-35 port. The net of those three features is a tidy and compact unit that does its job but stays out of your way. My unit has a 2.5 mm mini socket that will accommodate a (shades of sacrilege) Canon or Pentax remote control unit (or other camera remotes with a 2.5 mm connector), but the third-generation Pro model has the correct 10-pin connector for a Nikon remote.

The di-GPS unit draws its power from the camera and there were apparently some power drain issues with the first-generation unit. The second generation unit has a three-way switch that allows you turn the unit off, leave it always on (to maintain a satellite fix) or be turned on and off in sync with the camera’s state. It also provides better compatibility with the improvements Nikon made to the GPS feature in the D3 and D300 models. Besides the three-way switch the unit has a single red LED light that glows if the unit has a fix and blinks if it’s searching. I’ve used the unit on a Nikon D300 recording just shy of 2,500 GPS-tagged images over two months. Following are some observations.

Next: The Breakdown

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