Nader happens to be one of the best big crappie lakes in the country and the mapping for my 798 is horrible. My navionics south card shows no channels and only half the lake even shows contours. I have heard the Lowrance Insght is ok. But is there a fix for my HUMMER. All I need is a dashed line showing creek channels. Is there an update? or can I overlay a creek channel map somehow? THis sux.