The mathematics of roving searches

[Berserker]

I go to my patrol area and wait for a ship to come by,sink it and wait for the next one...I average about 30,000 tons per patrol...Anybody want a drawer full of navy crosses???

[ColonelSandersLite]

Yes, nautical miles.
Honestly, I got distracted by a shiny new thing, and need to come back to this. That shiny new thing led directly to the advanced convoy attack tutorial if I recall correctly.


The question about how often to dive for maximum search is a fairly complicated one and in your case, depends largely on two large unknown variables. Those variables being detection ranges for visual and hydrophones in RFB. Without knowing those, I can't even begin to speculate, except to say that I don't think that WCA should have a detection range of anywhere near 20 miles. I could be wrong on that, but I don't think I am.


The best thing you can do is just find the range for yourself. Here's how I did it:
I used a boat equiped with radar and WCA.
Map contacts on.
Detected target on radar, then turned radar off.
Waited for target to show up on hydrophones.
Turned radar on and marked position on map.
Measured distance on the map.

The same procedure was used for JP, just a different boat configuration.

I would be quite interested in knowing what numbers you get out of RFB.



I should run a test on it, but I suspect that in tmo at least, the answer is really simple. Basically, my suspicion is that you want to use the best sensor you have as much as possible. With radar, this is always going to mean surfaced. With JP and no radar for some reason (damaged radar for example), this would mean staying submerged as much as possible. With WCA, this would boil down to the current visibility level on the surface. I.E., surfaced during the day as long as weather is clear and submerged at night or in otherwise poor visibility.

If minimizing the enemies opportunities to detect you is the priority, you are trading away sensor effectiveness for stealth. Particularly by submerging during the day when sonar isn't your best sensor. In this case, you are reducing your effective search area quite substantially during the day, due to the lower search speed and lower detection radius. This stance would necessitate surfacing at night to recharge, and doing this would significantly reduce your detection radius if you are relying of visual detection.

[merc4ulfate]

I just hunt in the shipping lanes. It is easy to find ships with TMO and RSRD.

[Barkerov]

Originally Posted by ColonelSandersLite

I should run a test on it, but I suspect that in tmo at least, the answer is really simple. Basically, my suspicion is that you want to use the best sensor you have as much as possible.

Your suspicion would be correct becasue we are talking about circles and its easy to prove that the biggest one is best whether moving or stationary. S = 2rd/A where S = the sweep fraction, r is the detection range, d = the maximum distance of the search, A = the size of the search area.

I found this formula but I don't know how useful it is:
With a random search the probability of any given target being detected is then D = 1 - exp(-pS) where p = the probability of detection of a ship within the detection range r.

I think the answer with radar is simpler than it is with hydrophones. With the radar you can go with continuous sweep and so the only question that remains is how far back and forth do you travel. With the hydrophones you have to choose how far to go back and forth and also when to dive to use them.

[TorpX]

About the hydrophone detection; the early war equipment was probably only good to 7,000 or 8,000 yds. In RFB, the detection range is much greater, if you listen yourself. This however is a game bug, you can usually get a big advantage just by using the hydrophones yourself, while the crew performance is modded to be realistic. Don't know how much/when performance improved.

If you are trying to play realistically, your best bet is probably to submerge and go at most economical speed, 3 kn. during the day, and either sit still, or move at 6.5 kn. during the night (if you have enough fuel for that). On my last patrol, I followed the above procedure, only moving about 20 or 30 nm overnight to save fuel. This allowed for a fairly long patrol, while permitting me to cover a good chunk of my zone, bit by bit.

[Barkerov]

Originally Posted by TorpX

About the hydrophone detection; the early war equipment was probably only good to 7,000 or 8,000 yds. In RFB, the detection range is much greater, if you listen yourself. This however is a game bug, you can usually get a big advantage just by using the hydrophones yourself, while the crew performance is modded to be realistic. Don't know how much/when performance improved.

If you are trying to play realistically, your best bet is probably to submerge and go at most economical speed, 3 kn. during the day, and either sit still, or move at 6.5 kn. during the night (if you have enough fuel for that). On my last patrol, I followed the above procedure, only moving about 20 or 30 nm overnight to save fuel. This allowed for a fairly long patrol, while permitting me to cover a good chunk of my zone, bit by bit.

I just had a look at the uboat.net article on hydrophones.

"To avoid own noises, a submarine could use underwater sound detector if her speed was up to 6 knots. If a submarine speed was 4 knots, the submarine's underwater sound detector average distance of detecting another object was:

- for a destroyer- 5 to 10 nautical miles,
- for a cargo ship- 3.5 to 7.5 nautical miles,
- for a convoy- up to 50 nautical miles."

Obviously this is for U-boats though and it also doesn't say when. I would like to play as realistically as possible, but I have no idea how far hydrophones can detect ships in game or in real life, just that for the latter it varied a lot with weather conditions.

[TorpX]

In my recollection, the 7,000 yd. figure was for detecting a single ship 50%, detection, at war's start, so convoys, and maybe larger/noisier ships would be more easily detected. USN sound gear seemed to behind German equipment, at least at the start.

I can't remember where I saw this, but it was a surprise to me, as I had assumed the range was longer.

[merc4ulfate]

Sonar ranges when listen was greater than you think and less than you think depending on sea state and weather.

http://www.hnsa.org/wp-content/uploa...07/11730rb.mp3

http://www.hnsa.org/wp-content/uploa...07/11720ra.mp3 (reference to a 20,000 yard target being heard)

http://www.hnsa.org/wp-content/uploa...07/11722rb.mp3 (12,000 yards)

I love these recordings

[aanker]

Originally Posted by merc4ulfate

I love these recordings

Thanks for these merc4ulfate, I do too and didn't know these even existed in digital form. 'Roving Searches' assistance from the hnsa, how nice these were saved.

I even learned winter survival techniques (for winter camping) years ago and many other things from old WW II USAAF & USN films.

Happy Hunting!