i bought a lowrance Elite 4 DSI and was really excited about getting it on the water. but i am having some issue with the GPS portion of it. when i am in a major waterway it shows me on land. so i did a little reseach and it keeps pointing me into the direction of purchasing a card that has maps on it. do i really need to do this or is it a settings issue? would really like some feed back on it. not really wating to see all the charts and stuff. just wanted it to show a genral map with major canals and lakes. can any one give me some adive on this?