GARMIN DC 20 GPS Based Dog Tracking System for Multiple Dogs. GPS based dog tracking system Garmin International is pleased to announce, the Astro GPS enabled dog tracking system. Astro is the ultimate solution for the hunter who has spent many wasted hours searching for his four legged friends. Now you can release the hounds and know what they"re up to. The DC 20 is a transmitter that relays the dogs position to the Astro 220. It is mounted in the included, lightweight neoprene harness. The harness straps to the dogs collar, wraps around the chest, and behind the front legs. Users may also choose to fasten the DC 20 to an existing e collar by using the included collar attachment plate. Astro can track up to ten dogs at once and has the ability to update the dogs position every five seconds. In flat, unobstructed terrain, the Astro system can reach up to five miles. This system requires very little configuration out of the box. Once the transmitter and receiver acquire a GPS signal, the receiver will automatically display the location of the dog.