Nikon has supported GPS receivers connected directly to their cameras for years, while Canon's only solution was to use the GPS receiver to connect to wireless file transfer. clutch at a premium of hundreds of dollars. This device, which connects directly to the camera's electronics via the hot shoe on the 5D Mark III, 1D X and (cable) 7D flash, is the first device capable of geotagging photos during unattended shooting. WFT or other third party kit. And it's been rare enough since its release that almost nobody got to see it or get their hands on it until recently. So how well does it work? The answer is the same as any other modern GPS receiver. Actually suspiciously better. By that I mean this thing claims to have a satellite lock even though it's tucked away in the basement of a parking lot where there's no way it could possibly get a lock. That means she's lying. That's not too bad as all photos taken in these conditions will be tagged with something like the correct location unless you're going through the Laurel Mountain Tunnel or something. Canon's GPS locks in pretty quickly, and has the added benefit of a built-in compass, so when viewing geotagged photos (which obviously show the location of the camera, not what it's pointing at), you can tell which direction the camera is headed Camera pointed at it. From here you can define the scene. You hope. This addition of compass direction to EXIF data is a rare and important thing. Finally, a GPS device is about the size it is because it needs a patch antenna about the size of the device to be able to maintain a lock through a reasonable number of obstacles. Anyone who complains about their size doesn't understand GPS. Yes, there are smaller GPS modules the size of wristwatches, but they keep losing lock. They're only used for average info like tracks and distance traveled, so those constant blocking breaks don't matter. The Canon GPS needs to remain locked for as long as possible as its information is only used for a short time during recording. Therefore, he needs a large antenna. However, it will "wander" from time to time, meaning that with a large set of images, one or two outliers may be offset by several hundred feet. Don't take what this thing says as truth in all cases. However, it works well enough for a device made by a company that doesn't specialize in GPS receivers, and the accompanying software and firmware seem to do the job. If I have any complaints, it's when the device is connected to the computer, it doesn't identify itself as a mass storage device via USB, so it doesn't mount directly to the desktop. The only way I know of to get GPS data is to use the included Sony software. Nothing else will work. And I also don't understand how to wipe data from device. So four stars in total.