ive searched high and low but im new to fishing with all this new technology...ive looked at navionics online and I know how to use the maps to find certain depths but still not good at what all the circles and different direction lines mean....Ive tried to find a map key or something that explains how to read those maps...best i know is that when lines are really close together there is a steeper drop in depth of that area...I can also tell where major rivers are located but as far as all the circles and rounded lines dont understand that part of it..