system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How did the Vikings and other seafarers of yore manage to sail to specific locations (ports, beaches) when the compasses they had only indicated direction?

Compasses can indicate direction but not really the specific paths they would have to take to reach specific ports or beaches. So although those sailors would have known that they're going, say, a direction like SSW, how could they know that they're on the right path to hit the port or beach they wanted to get to? If their boats were to "drift" sideways, they'd still think they're going the right direction, but could end up hundreds of miles off target, right?
gpt
Most "seafarers of yore" overwhelmingly tried to keep within sight of a coastline whenever they could. In situations where this wasn't possible, they referred to the stars, ocean currents, and (when available) compasses. Vikings were pretty good at this, Polynesians were *great*.

It is hard to overstate just how important the invention of reliable timekeeping was to navigation. Once you know the math, you can reckon your latitude pretty easily from the sun and stars, but calculating longitude without time or landmarks is **really hard**. 

Shortly before naval chronometers really took off, one competing plan was to set up beacon stations which set off fireworks, every hour, **across the entire ocean**. Fortunately (unfortunately?), this plan was never implemented.