| Beyond what everyone else has said here, it's also just not as easy to interpret GPS location on maps. Say you're in the middle of an ocean, nothing but water everywhere around you. You're rocking on pretty good waves, going a nice 8 knots. You look at your GPS. You can see where you are right now. You can see a bit further away there's a dangerous rock which you should avoid. How do you interpret from looking at the map whether or not you're going to hit it? Your GPS might show you your bearing, but because of the waves it's oscillating 10 degrees every 5 seconds. You don't know your leeway (drift because of the wind) nor if any current might still push you into the rock. This is, of course, all calculable. But still, according to the map it's not that far away. It's hard to interpret on a feature-less ocean, and on a GPS map, whether something is 5 or 10 or 20 meters away. You're getting closer, but according to your calculations you shouldn't hit it. Hmm, did you calculate it correctly? Has the wind changed? Have the currents shifted? You look at your GPS again, the rock looks a bit closer now, but you're not sure whether that's to be expected or whether that's indicative that you might hit it. Either way, this hypothetical situation might give you a bit more of a sense on what it's like to be on a boat. Things are pretty vague, and even if your phone could say "that rock is 30 meters away", it probably won't be able to say whether you're going to hit it or not with a degree of certainty that you want to risk your life on until you're well away from it. It's hard to explain how it feels like to navigate "by instrument" on a featureless plane like this. But if there's a buoy floating, marking that rock, you can see it right there. Your human brain can easily interpret whether you're going to hit it or not, and it gives you confidence that you won't if you can see it really clearly. It's also a mark that you can use to navigate to, e.g. "I need to keep bearing X, that's approx in the direction of that lighthouse on the horizon right there" (or "I need to keep it 20 degrees off the bow"). That is much less fatiguing than steering based on a compass that is continually shifting due to the waves. I guess it's a bit similar to the difference of flying planes through clouds on instruments versus using sight. Using visuals is much easier, and much less prone to errors, which is important because if you do make a mistake it can be very dangerous indeed. Not like with a car where you can just stop or you see when you're going to run into a wall or a pond. |
I can see everything easily on the GPS map, and see where I've been going, and I can steer to go wherever I like. Currents and wind and stuff don't affect me much, because I don't look at which way the boat is pointing, but which way its heading on the map (which includes the effects of currents and wind).
The only annoying thing is anything that doesn't show on the map. Like floating logs, men overboard, etc. Those are a pain because I have to look out of the window and try to figure out where they are on the map! And sometimes if it's foggy I can't see those things at all!