The 581i DI unit should have the same specs As the 570 DI model plus the GPS stuff (internal GPS Receiver, additional waypoint, track and routes capability, plus mapping and can use the LakeMaster and Navionics mapping cards). It has the same two 2D sonar beams and the same two DI sonar beams as does the 570 DI model.

Direct e-mail me if you would like a an electronic copy of the operations manual.