Since you have the old one you know that they are not accurate. The new one’s have lakes that have been surveyed and are done in 1 ft. contour lines. You can go to http://www.navionics.com/HotMapsPrem...asp?RegionID=2
The ones in red are the new High-Definition Lake Surveys… I have the new south one on order. Hope that this help....Also navionics has a $75. trade in progam for your old chip