How far is the Horizon?

[Guest]

I am having a bit of a heated debate with my wife as to how far the horizon is. I would like to know how far you can see, with normal eyesight and whether standing on the shore or high up on a posh motor cruiser would make a difference. She is adamant that it is 7 miles, any offers?

 

[lyc]

Look at Broads & East Coast Boating

 

[msimms]

From <A target="_blank" HREF=http://www.boatsafe.com/kids/distance.htm>http://www.boatsafe.com/kids/distance.htm</A>

1.17 times the square root of your height of eye = Distance to the horizon in nautical miles.

Cheers

Mark

 

[Col]

Interesting site, notsure of its accuracy. 10ft high=horizon under 4 miles????

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[Guest]

Well the debate has now turned into a row, I thought it was further, but it seems that website is correct. Neither of us are winning at the moment !!

 

[jimi]

look at page 69 of Reeds, height of eye 9.8 feet horizon is 3.6 Nm

 

[Guest]

Great Jimi, my 2003 copy of Reeds had just arrived (together with the free waypoint & marina guide) after a loooong wait from the RYA, I did not realise there was so much info in it. I think I have enough to read there for months!! Great value.

Cheers mate,

 

[Col]

Actually, thinking about it, I was thinking of the view when looking at IOW which is more than 4 miles away, It's not on horizon.
Should have remembered dipping distances. I know I'm wide of the mark when I think along those lines.






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[Guest]

Col. Well I was confused at the fact that you can see France from Dover, so you are not the only one, but I don't even know about dipping distances yet, so you are well ahead of me. Looks like another book I will have to buy /forums/images/icons/wink.gif Do they make bookshelves for Glastron cuddy's ? /forums/images/icons/laugh.gif

 

[Col]

Fer gawds sake Grumpy, when you launch that boat, it's gonna go straight down the slipway....................underwater /forums/images/icons/laugh.gif

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[Trevor_swfyc]

Re: Horizon Distance

This does depend on how high you are, your wife is right if she is 13.25 metres to her eye height.

The formulae I have found is 1.92 x sq root of the height in metres.

It goes on to say that the refractive index of light in the lower layer increases this distance to 2.08 x sq root of the height in metres.

Note it is normally quoted that a VHF radio is line of sight so an arial 10 metres up will be picked up 5 - 6 miles away.

Lets hope you are happy /forums/images/icons/smile.gif with this answer.

Trevor

 

[Guest]

I am so, so impressed by the intelligence on this forum, that I am starting to think I am the only real person and you are all auto reply machines linked to a knowledge data base /forums/images/icons/wink.gif. How would it be possible in a lot of other circumstances to get service like I have just had. It is far quicker than the help desk at the RYA, if you can get through to them that is. Thank you so, so, much for your help and guidance.

 

[Guest]

Re: Horizon Distance

Trev, please don't confuse me, you all know too much. I have my VHF course tomorrow, boy will I have some more quesions and books to buy or what /forums/images/icons/laugh.gif Very interesting though, I will ask about the line of sight tomorrow in class, they will think I have been preparing well for the course /forums/images/icons/wink.gif

 

[BarryH]

I'm just waiting for "MY boats sunk" thread. Then I can tell you all about lift bags and how best to scrap a Glastron.........mmm, wonder how long that'll be!

 

[Guest]

It's OK Barry, I'm an advanced diver /forums/images/icons/wink.gif I have a good selection of lift bags, and all the recovery gear /forums/images/icons/laugh.gif I haven't worked out how to fit all that gear on the boat yet. You know, I was thinking that I may just need one a tiny bit bigger, because IF it does sink, I've lost the lot /forums/images/icons/laugh.gif I have been concerned because there are a lot of dive clubs booking trips to the mouth of the Chatham marina on the 22nd March, don't know what is going on there, do you /forums/images/icons/laugh.gif

 

[Trevor_swfyc]

Re: OVER & OUT

Happy1,

Good luck tomorrow whatever you do don't say over & out that may be a good wind up usually guarantees a fail.

We had a radio test but the instructor did not have a mock up radio so we had to pretend. I was asked to explain how I would ask a yacht leaving a marina if there was spare spaces in the marina. Silly really because there must be at least one with me. Anyway I thought I did well but was told I forgot to turn it to 5 watts I replied it was already on 5 watts /forums/images/icons/wink.gif. Fortunatly the examiner had a sense of humour and I passed.

Good luck.
Stay /forums/images/icons/cool.gif
Trevor out

 

[Guest]

As has been pointed out, your Almanac contains a table of dipping heights, but for an eye level of 6ft, the horizon is about 2 miles, from memory. Standing on deck in Studland bay (eye height about 3m), the Needles lighhouse dips below the horizon with the swell. Distance is about 10 miles.

Yuo can see France from Dover cos you're stood high up, and you're not looking at surf breaking on the beach in Calais, you're seeing hills behind...

 

[Guest]

Re: OVER & OUT

Trev, it seems to be a very long day 9am - 5pm, don't know if I have enough to say to fill all that time, I will let you know how I get on, Over & Out /forums/images/icons/laugh.gif

 

[tr7v8]

Re: OVER & OUT

Nah, the correct bit is Roger, Over & Out, Oh and to call someone go to Channel 16 and go 10 4, 10 4 are their any truckers out there..../forums/images/icons/smile.gif

Jim
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