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Why Is It So Difficult to Map the Ocean?

nautil.us

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Re: Why Is It So Difficult to Map the Ocean?

#31

Post by troupo »

RcouF1uZ4gsC wrote: post #6

I bet the US Navy has classified ocean floor maps that are far beyond those available to the public. Knowing the ocean floor better than your opponents is likely to be a big advantage when playing the various cat and mouse games with attack and ballistic missile subs that the US and the Soviet Union played for decades.

Submarines still travel in what are basically shallow waters, there aren't that many of them, and mapping ocean floor isn't their primary mission. So, however detailed those maps are, I'd wager that they are still largely "here be dragons".

Re: Why Is It So Difficult to Map the Ocean?

#32

Post by dragonwriter »

nabla9 wrote: post #10
RcouF1uZ4gsC wrote: post #6

I bet the US Navy has classified ocean floor maps that are far beyond those available to the public. Knowing the ocean floor better than your opponents is likely to be a big advantage when playing the various cat and mouse games with attack and ballistic missile subs that the US and the Soviet Union played for decades.

Still not good enough. US Navy subs have underwater collisions from time to time. In 2015 USS San Francisco collided underwater sea mount at full speed. It was supposed to be deep blue sea. In 2021 USS Connecticut collided with underwater mountain in South China Sea. US Navy needs to map ocean floor only to 500 meters to keep it safe for submarines but they can't even do that.

> In 2015 USS San Francisco collided underwater sea mount at full speed. It was supposed to be deep blue sea.

First, it was 2005, not 2015.

Second, the seamount they struck was marked on charts the crew had as a potential hazard, they failed to review those charts and transfer the notation to the chart used for navigation.

> In 2021 USS Connecticut collided with underwater mountain in South China Sea.

And not long before that, with a pier at Naval Base Point Loma.

Re: Why Is It So Difficult to Map the Ocean?

#33

Post by sandworm101 »

emmelaich wrote: post #7
jpm_sd wrote: post #2

Because we have to use sound waves instead of radio waves. But the article is mostly about satellite based gravimetric mapping techniques which are fundamentally low resolution.

You can use laser, but that's only good for up to around 50m deep. https://www.dst.defence.gov.au/innovation/laser-airborne-dep...

50m of clear blue Caribbean paradise water. Or 5cm of turbid Amazon river outflow.

Re: Why Is It So Difficult to Map the Ocean?

#35

Post by pauldenton »

nabla9 wrote: post #10
RcouF1uZ4gsC wrote: post #6

I bet the US Navy has classified ocean floor maps that are far beyond those available to the public. Knowing the ocean floor better than your opponents is likely to be a big advantage when playing the various cat and mouse games with attack and ballistic missile subs that the US and the Soviet Union played for decades.

Still not good enough. US Navy subs have underwater collisions from time to time. In 2015 USS San Francisco collided underwater sea mount at full speed. It was supposed to be deep blue sea. In 2021 USS Connecticut collided with underwater mountain in South China Sea. US Navy needs to map ocean floor only to 500 meters to keep it safe for submarines but they can't even do that.

https://en.wikipedia.org/wiki/Ehime_Maru_and_USS_Greeneville... There's other kinds of Sub collisions as well

Re: Why Is It So Difficult to Map the Ocean?

#36

Post by dylan604 »

gleglegle wrote: post #34
nabla9 wrote: post #27

If you have 100 ocean survey ships scanning the ocean floor 24/7 moving 6 knots with 1 km wide side scan sonar, it takes over 900 years to map all oceans.

10,000 autonomous ships to do it in 9yrs?

with what funding for that many ships for what purpose of recovering the investment?

Re: Why Is It So Difficult to Map the Ocean?

#38

Post by dylan604 »

nradov wrote: post #28
nabla9 wrote: post #10

Earlier quoted context omitted.

Still not good enough. US Navy subs have underwater collisions from time to time. In 2015 USS San Francisco collided underwater sea mount at full speed. It was supposed to be deep blue sea. In 2021 USS Connecticut collided with underwater mountain in South China Sea. US Navy needs to map ocean floor only to 500 meters to keep it safe for submarines but they can't even do that.

The US Navy reports from the 2005 (not 2015) USS San Francisco and 2021 USS Connecticut groundings can be found here. In both cases primary blame was placed on the crew, although charts were a contributing factor. https://www.cpf.navy.mil/FOIA-Reading-Room/

If you have accurately marked charts but fail to use them, charts were a contributing factor. However, it is the human error that was the blame.

Re: Why Is It So Difficult to Map the Ocean?

#39

Post by checker365 »

nabla9 wrote: post #27

If you have 100 ocean survey ships scanning the ocean floor 24/7 moving 6 knots with 1 km wide side scan sonar, it takes over 900 years to map all oceans.

Could I know your formula?

ocean : 361,000,000(km2)

6knots: 11.1km/h

361,000,000/(24*365) = 41,096(km2/day)

41,096/11.1 = 3,702

so, 100 ships take 37years?

Thank you, klaus23!

Re: Why Is It So Difficult to Map the Ocean?

#40

Post by Klaus23 »

checker365 wrote: post #39
nabla9 wrote: post #27

If you have 100 ocean survey ships scanning the ocean floor 24/7 moving 6 knots with 1 km wide side scan sonar, it takes over 900 years to map all oceans.

Could I know your formula? ocean : 361,000,000(km2) 6knots: 11.1km/h 361,000,000/(24*365) = 41,096(km2/day) 41,096/11.1 = 3,702 so, 100 ships take 37years? Thank you, klaus23!

I'll throw my result into the ring. I get 37 years:

https://www.wolframalpha.com/input?i=%284*pi*%2812733km%2F2%...>

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