Sound, haven't seen a bass care about sound. Boat moving through water, walking on deck, bait hitting water, talking, music, coughing, motor prop, sonar pings etc all make sounds..
GPS positioning, depends a lot of where you're placed to get a signal. If I'm under a bridge I can get a good lock no matter what I'm using. Bad enough my cars Garmin have to await accuracy every time I turn it on. There have been times where I've been locked dead in a spot and other times I've move around 15 ft (in current)