Out of sight of land, how far is that?

[Superflid]

Been reading the other thread but have a question of my own.
Having only recently managed to lose sight of my mooring ropes it's probably not going to happen just yet, but how far out would I have to be before losing sight of land?
Bear in mind that the deck of my boat is more or less at sea level and most of the land around my cruising ground of The Wash is even lower!

 

[duncan]

I expect to see landfall at about 8-10 miles - but that assumes a more usual cliff / hilly foreshore.

If it's seriously flat flat then you are looking at the visible horizon - which is gogin to be very dependent on whether you are standing up or sittng down! However 3-4 miles maybe.

 

[Superflid]

This is the coastline from about 100 yards out! My friend Mac didn't seem to like the noise of my diesel lump, must get it boxed in. /forums/images/graemlins/grin.gif

Looks like I could be out of sight of land much sooner than I thought....

 

[Major Catastrophe]

This is the furthest I have been out.

The mountains are Snowdonia.

I left port before dawn, so it was not quite so scary being so far out as I was too pre-occupied in trying not to hit pot markers.

 

[Medskipper]

Only about 50 yards then! lol!

Barry

 

[Kawasaki]

Is that picci off Llanddwyn, by any chance? /forums/images/graemlins/wink.gif

 

[Rustyknight]

On one channel crossing, we could see both the Cherbourg peninsular behind us, and the cliffs of the Isle of Wight ahead........ other trips it's only been until a mile or so off we've seen land, so a lot depends on the weather.

For some reason, the further off you can see land and p'raps your destination, the more tempting it is to forget the passage plan and carefully plotted "course to steer", and head straight for port. Not wise if the tides are strong, especially at 5 knots!

 

[Salty John]

We were crossing the Great Bahama Bank and the keel touched the bottom, but we were out of sight of land! We could see starfish under the boat, but no land in sight - very strange. I reckon land was only 4 miles away, but the Bahamas are very low lying.

 

[NorthernWave]

I'm about to do that passage in two weeks, I normally head up the old bahama channel but thought I'd give the bank a go then if the crew get tired we just go snorkelling!! LOL

But your right it really does depend on the mountains, high rises or just flat shape of the land.

 

[Superflid]

Just had a look at the Ordnance Survey map around Boston for contour lines.

There aren't any! Just the odd spot height here and there, mostly around 2 or 3 metres.I knew it was fairly flat, but that's just ridiculous......

 

[Major Catastrophe]

[ QUOTE ]
Is that picci off Llanddwyn, by any chance?

[/ QUOTE ]

Spot on, but a bit further out into Irish Sea.

 

[Deleted User YDKXO]

There is a scientific answer to this question and the distance away from land at which the land just dips below the horizon is given by

Distance = 2.08 × (sq rt:eye height + sq rt:height of land)

where the distance is in nm and the heights in m. So if you are sitting on your flybridge at a height of 4m and approaching land which is 10m high, you will just see it rise above the horizon at about 10.7 nm range assuming that visibility is perfect which of course it hardly ever is

You can do the same calculation using dipping range tables in most almanacs which are designed to be used for calculating the distance at which you can see lights

 

[Superflid]

Land at 4m (Sea defences around The Wash) and eyes at 2m gives about 7 miles, sounds like I shouldn't lose sight of land until I venture out of The Wash, or it gets foggy.

 

[bdsweeting]

I think someone said that at your normal 2m eye level it was about 2.5 to 3 nm to the surf line. Obviously the land rises above that but there you go.

 

[coastwise]

Looks like Tabs Head viewed from the NE to me.

 

[Superflid]

Could well be right, the figures are from the formula given by Deleted User.

 

[Superflid]

[ QUOTE ]
Looks like Tabs Head viewed from the NE to me.

[/ QUOTE ]

Certainly is, just not too far NE.... /forums/images/graemlins/grin.gif

You're not the skipper of the expensive looking sports/fisher type boat which seems to think I know where the fish are, just cos my boat looks like I should know are you? It was heading out from the Welland just before I took that pic last friday lunchtime.

The weekend before he had followed me to where the fish obviously were (cos mine is an old fishing boat!). We obliged his delusion by hanging lumps of lead onto a couple of fishing lines and dangling them over the side while we drank tea and ate biscuits! /forums/images/graemlins/laugh.gif

Does anybody here know how to catch fish? I might as well learn....