How does a lighthouse helps ships navigating?
In: Engineering
Apart from the stuff that is pretty self explanatory, which is that they are (mostly) built on land (or shallow ground), so you intuitively know you shouldn’t get close, there are a couple things to add: Paired with a compass (which is standard equipment on any ship) you can narrow down your position on a map to a line. The only missing piece of information you now need to completely locate yourself, is the distance, which you have multiple possibilities to measure. Either through direct ways, sonar(measuring the depth of the water under you and cross checking with a map), or supported by GPS. Also lighthouses have different sectors, where they (seemingly to you) flash their light in different time intervals. Passing these sectors and comparing and cross checking with a map, you can understand what exactly your position is and navigate safely from there.
They were basically giant hazard warning lights. They were built where ships were at risk of running aground or afoul of especially shallow water. So you’re out at night (especially in a time when electric illumination was rare or didn’t exist) and you see one light off in the horizon and you at least know to keep your distance because that’s where the shore begins and you don’t want to run into it.
Or if you’re looking for a port that can be a sign too.
Today with the advent of radar they aren’t as effective anymore and ones you might visit aren’t functional anymore.
At night the sea is black, and so is most of the land. The only thing that ships will see during the night is lights from houses, towns, other ships and lighthouses. So if someone is heading right towards a light then they must have done some wrong navigation and needs to slow down to avoid crashing into it. Lighthouses will focus their lights in a single direction to make them stronger. This was more important when the light were candle or gas lights but is still a feature on most lighthouses. The focusing lens will rotate so from a ship it looks like it is flashing. All lighthouses have different lenses and rotates at different rates so it is possible to identify which lighthouse you are seeing if you know the pattern. This makes it much easier to navigate along the coast as you can use the lighthouses as reference markers for when you should turn. Nowadays with modern GPS and radar the lighthouses does not serve as much purpose any more. However it is still saving lives as people may not always pay attention to the screens but are more likely to pay attention to a light. In addition both GPS and radar can and have been jammed either accidentally or on purpose.
Prior to GPS, you had to use a map, compass, sextant, and the stars to determine where you were and get from place to place. These are only accurate to a degree, as maps were often somewhat incorrect, your compass can sometimes be slightly off due to interference from metal around you etc. If you were able to get within a few miles of land, you often couldn’t see it at night- back then cities didn’t light up the coastline like they do today. A lighthouse is built tall, the taller (and brighter) the better, as a higher vantage gives you a better beyond-the-horizon capability. A 100 foot tall lighthouse can be seen from 16 nautical miles away. So if your maps and sextant got you into the general area, the lighthouse could guide you home. Also, to avoid reefs that could damage your ship, the other function of a lighthouse was to give you a point of reference on your map to give you an approach to shore without rubbing aground. If you are approaching a lighthouse from due west, and your map says the reef is 500 yards due east of the light house, you know to change course to go around it, or drop anchor.
They are painted in high contrast colors to stand out as much as possible during the day and serve the same general purpose.
It allows ships to know where the coast is in the dark or bad weather, so they can avoid running aground
A ship approaching the shore at night, in fog, or in a storm might not know exactly how far it is to the shore. Or precisely where some nasty rocks on the map are relative to where the ship is (because they had no way of knowing exactly where the ship was). A lighthouse would be the first thing ships saw as they approached the shore, and would warn them to at the very least veer away from the lighthouse.
It was just a signal, the light didn’t actually reveal anything other than where the shore or hazardous rocks were. It didn’t aid navigation, other than showing the ships where to *not* go once they were close enough to see the lighthouse.
Nowadays they are still useful in some places, particularly in foggy areas where you can’t see anything, but other technologies like GPS and SONAR and RADAR – and *much* better maps – are better able to tell you where you are, where the land is, and where any dangerous rocks might be. But back in the mists of time they were the *only* way of keeping ships off of the rocks.
They let you know that you are x distance from shore. This helps when it is foggy/storming because you see the light cutting through the fog/rain and can use it to navigate.
I dont know the exact distance they are meant to be.
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