Expanded dog capability - track up to 20 dogs from a range of upto 9 miles GPS/glonass - high-sensitivity GPS and glonass satellite receptionhas the ability to track in more challenging environments than GPS alonePreloaded mapping - includes preloaded topo U.S. 100K mapping and a free 1-yearbirdseye satellite imagery subscription Hunt metrics - hunt metrics dogperformance data shows distance traveled, time afield and more, so you cantrain your dog more effectively Optional battery - optional in-unitrechargeable nimh battery Pack or uses standard AA battery power