I’m new here, new to my lake and am hoping for advise about choosing the important features for a fishfinder. I’m thinking I want GPS assuming it will help me relocate good fishing spots and I would like good graphics down to 100 feet so I can tell if I’m over various structure. Also I’m not sure what “down imaging” and “side imaging” would do for me but I assume it would contribute to accurately identifying structure. Are there features, not mentioned, that are necessary? The boat is a 21' Tracker pontoon. All advise will be appreciated - Bill