Ship Radar systems

abctriplets

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Ok, just a quick question about ship radars. If you've got a large research vessel - how far would the typical range of a radar system be? For example, how far away would another ship have to be for it to not be seen?
 

PeterL

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It is basically about 20 miles, but it depends on how far above the surface one is.
 

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I had too Google that. According to Wiki there is short range and long range radar. "The newest radars fire 2 pulses during one cell, one for short range 10 km / 6 miles and a separate signal for longer ranges 100 km /60 miles." But that's just how far the radar can go, it doesn't tell you how far the horizon is.

But I also found a formula for figuring out how far you can SEE.

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

So if your eyes are 6 feet above the surface of the water, the formula says you can see about 2.8 miles. 25 feet up and you'd be able to see 5.85 miles
 
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abctriplets

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Ah thanks so much. So depending on the range, it seems 6miles-60 miles, possibly less depending on the horizon. I tried googling, but not knowing much about ships, I was quickly overwhelmed.

And that's a neat formula for unaided distance - though at first I thought you were saying people with larger eyes could see farther :)
 

Noah Body

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Ok, just a quick question about ship radars. If you've got a large research vessel - how far would the typical range of a radar system be? For example, how far away would another ship have to be for it to not be seen?

Here you go...

Furuno Radar Systems

I have a 64kw open array on my boat which has a listed range of 48NM, but it's never reached that far. If I had a tuna tower, I'm sure it might.

Check out other vendors as well.

Also understand that sea state and other obscurants will reduce the book range as well.
 
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Stanmiller

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Ok, just a quick question about ship radars. If you've got a large research vessel - how far would the typical range of a radar system be? For example, how far away would another ship have to be for it to not be seen?

There's another factor.
Height above waterline of the target has to be taken into account. If both antenna and enough of a target to generate a reflection are the same height, say 25 feet as ferret gives for an example, then the detection range would be doubled.

Naval surface search radars are stated to have ranges in excess of 50 nautical miles (exactly how much in excess is classified).
 

thothguard51

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You also have to take into account the fact that the ocean surface, while flat, is bowed due to the curvature of the earth. If the seas are rough, your line of sight to the horizon is decreased. So height plays an important role, which is why you want your radar dish set as high above the deck as possible. A standard ship with multiple decks above the surface could have a radar dish set 50 or more feet above the waterline, thus increasing the distance to the horizon. There is also satellite to consider which sees over the horizon and can be tapped into.

While radar for spotting planes is the same as that used for spotting surface vessels since planes travel at a higher attitude they can be detected hundreds of miles out. Which is why if a plane drops below a certain altitude, radar does not pick it up...the horizon block it, on land or sea. Once again, many radar systems also rely on satellites if there is a need for extended ranges beyond horizon. This includes weather forecasting for ships to track...
 

justAnotherWriter

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Some very good answers here, so I'll just add a tidbit about practical application...

I had a Radar with a 16nm range on top of a 50' mast, but I could rarely get anything past 12nm. So whatever the range you decide to use, knock some off the top to account for interference, waves, etc.
 

RobinGBrown

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and don't forget that some radar equipment will be for finding planes not ships.

A plane can theoretically be seen a lot further away than a ship becases it's way up in the air with nothing in the way.
 

RJK

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If you're referring to modern U.S. naval ships, you'd probably be using a Spruance class hull, which most destroyers and cruisers are built from. They carry a surface and and air search radar. For surface search, a contact (depending on how large it is) begins to paint at about 22 nautical miles. We normally kept our range scale at 25 or 30 miles.
Air search is a different animal. It depends on the altitude of the aircraft. Two hundred miles is not unusual for picking up an airliner at 30,000 feet.
If you were on a personal craft, use the formula provided above.