Due to the curvature of the earth, how far can you see something on the ocean? Assume binoculars, etc.
Question For you Nautical Types
- Thread starter max
- Start date
Register to hide this ad
OP
Due to the curvature of the earth, how far can you see something on the ocean? Assume binoculars, etc.
canoeguy
US Veteran
From a canoe or kayak, an object just visible on the horizon, like an island with trees, buildings, water tower, etc. is approximately eight miles away.
From a larger (taller) vessell, objects on the horizon will be sighted farther away.
From a larger (taller) vessell, objects on the horizon will be sighted farther away.
rewster
Member
On a clear day you can see forever
rcnixon
Member
Here ya go! As they say in the math books, the solution is left as an exercise for the reader:
http://www.wolfram.demon.co.uk...orizon_distance.html
Russ
http://www.wolfram.demon.co.uk...orizon_distance.html
Russ
Here's a non-quantitative answer. While standing in the superstructure of a ship, estimated to be 30-35 feet from the water, one a clear day, we could see large objects (other ships) approximately 25 nautical miles out.
VAdoublegunner
Member
Being an avid sea kayaker, I can tell you that you don't see that far. The estimate of 7.5-8 miles is right. On a good day, if standing on the beach about 4 ft above MSL with me being over 6' tall, I can see across Chesapeake Bay, about 14 miles where I paddle.
I just hope those in bigger boats can see *me* well enough stealthing among the whitecaps
. Especially jetskis ... fortunately there aren't many of them, just locals where I kayak most and they are pretty cool.
You also get this interesting 'magnification' effect of distant objects from the air density being different that close to the water.
I just hope those in bigger boats can see *me* well enough stealthing among the whitecaps
You also get this interesting 'magnification' effect of distant objects from the air density being different that close to the water.
CW Spook
US Veteran
It depends on your height above the water and the height of the object on the horizon. Here's a calculator: http://www.qsl.net/kd4sai/distance.html
Smitty500Mag
Member
Originally posted by VAdoublegunner:
I just hope those in bigger boats can see *me* well enough stealthing among the whitecaps. Especially jetskis ...
I feel your pain. Jetskies are good for one thing and that's for chasing with your boat and scaring the hell out of the idiots driving them.
Smitty
MKT
Member
If I remember correctly, flat earth (same as water) is something like 16 miles horizon to horizon. So, if you are at sea level, say a small boat, you can see 8 miles. Now if what you are looking at is tall and rises significantly above the horizon, technically you can see farther. Same goes if you are in the wheelhouse of a multi deck ship, you can see farther than the 8 miles to the horizon.
5Wire
Member
Serious navigation, use the calculations.
At an eyeball height of about eight feet above water level, I couldn't see beach sand at half tide outside of five miles unless there was a sea running. Kind of now you see it, now you don't thing.
At an eyeball height of about eight feet above water level, I couldn't see beach sand at half tide outside of five miles unless there was a sea running. Kind of now you see it, now you don't thing.
doublesharp
Member
I always heard 7 miles.
5Wire
Member
Originally posted by Miss Fire:
I can see Canada from the nearest shoreline
I spent some time in Gananoque Ontario where a friend of mine was raised. The Gateway to the Thousand Islands. There were some specialized smuggling craft that plied those waters back in the day, and maybe still, in both directions. Out on the water I couldn't tell what country I was in never mind which one I might be looking at.
As pointed out already, distance of visability to an object is dependent on height of observer above water surface(height of eye) and height of object being viewed above water surface.
HO Pub#9,"American Practical Navigator"(AKA Bowditch)has nav tables in the back,table #8 is for distance to the horizon for various heights of eye.
The distance an object can be seen is the sum of the observer's dist to horizon and the object's dist to horizon.
Examples
6'ht of eye = 2.8 nautical miles(3.2 statute miles)to horizon. FROM TABLE #8,HO Pub#9
20' ht of object = 5.1 nautical miles(5.9 statute miles)to horizon. " " " " "
Distance object can be seen = 2.8 nautical miles + 5.1 nautical miles = 7.9 nautical miles.
100' ht of eye (wheelhouse level of large ship) = 11.4 nautical miles to horizon
500' ht of fictitous Light House on mountain top = 25.6 nautical miles to horizon
Distance Light House should break horizon(become visable)= 11.4 + 25.6 = 37.0 nautical miles.
Of course this is dependent upon a clear atmosphere, meteorological unlimited visability.
The 2nd example is what was used before the days of radar and electronic nav systems by a ship approaching a coastline. Table #8 provides solutions that are quite accurate.
For something to do I used to use a World Trade Center tower when we were inbound to NYC.
Kevin
HO Pub#9,"American Practical Navigator"(AKA Bowditch)has nav tables in the back,table #8 is for distance to the horizon for various heights of eye.
The distance an object can be seen is the sum of the observer's dist to horizon and the object's dist to horizon.
Examples
6'ht of eye = 2.8 nautical miles(3.2 statute miles)to horizon. FROM TABLE #8,HO Pub#9
20' ht of object = 5.1 nautical miles(5.9 statute miles)to horizon. " " " " "
Distance object can be seen = 2.8 nautical miles + 5.1 nautical miles = 7.9 nautical miles.
100' ht of eye (wheelhouse level of large ship) = 11.4 nautical miles to horizon
500' ht of fictitous Light House on mountain top = 25.6 nautical miles to horizon
Distance Light House should break horizon(become visable)= 11.4 + 25.6 = 37.0 nautical miles.
Of course this is dependent upon a clear atmosphere, meteorological unlimited visability.
The 2nd example is what was used before the days of radar and electronic nav systems by a ship approaching a coastline. Table #8 provides solutions that are quite accurate.
For something to do I used to use a World Trade Center tower when we were inbound to NYC.
Kevin
