I'm building a fishing vessel and a couple of drones with wide band radar seemed like just the ticket to finding the fish.
So, I need a barrier rating for radar, not shooting a bullet through it.

As far as i know radar sucks royally for looking through water - you'd better use a sonar (and the sonar sucks above it, so you'd better use both)

You have to be touching the water to use sonar under the water.

Water soaks up radar like a sponge.

Sonar is about the only real option.

It's that way in the game, it's that way in real life as well.




-k

I don't think water soaks up radar better than concrete, does it?
Rating 4 Ultra-Wide band radar will penetrate 20 points of barrier rating.

And if you were talking about, say, four feet of water suspended in mid-air, then sure, Rating 4 Ultra-Wide Band Radar might still work.

You're talking about the frigging ocean. A Rating 4 ultra-wide-band radar will probably get you a good four, six feet of readings.


The ocean's known for being a mite deeper than that.

… Why do you even need to find fish?

I'm assuming he doesn't need to find fish, so much as look like he's out looking for fish

Found this via google: http://www.physlink.com/education/askexperts/ae456.cfm

A little outside research can sometimes do wonders for in-game application.

Yea, just need to look good. Of course, if there's a bunch of fish in the hold, the whole thing looks a lot more real. Especially when the smuggler compartments are in the bottom of the hold. Get 2 tons of fish on top and the USCG isn't finding anything. That will also stop the astral snoop.

Good link, thanks.
Sadly, it doesn't help.
I'm not expecting it to map the deep ocean floor. I'm trying to locate salmon or tuna 1 - 50 meters below the surface.

Water stops radar-frequency radio waves cold within just a few feet.

If the fish are within that range, then maybe yes, you can use radar to find them.

Then again, at that point you could just look using your eyes.





-k

psh. using your eyes is soooooo 2060. get with the times, man!

How does that stop astral snooping? They'd have to be *living* fish packed all around the hiding place.

he needs to catch live lobster!

If the fish in the hold are alive, it stops astral snooping. Having enough water in there is a pretty common thing, I think.

As far as I know it's not common, unles you're fishing things like lobsters and the like. The holds are only refirgerated very close to 0°c to make sure the fish keeps (most fishing boat operate close to the port, with a fishing trip under 12 hours).

A water-filled hold is usually a bad idea in a boat as seveal tons of water sloshing around can easily capsize a small boat.

Even modern fish finders use sonar. Is there some reason beyond the slight capacity difference that you don't want to use sonar for your boat? It's cheaper than the UWB radar as well. As has been said, fishing boats don't roam about full of water and live fish. The big commercial ones tend to flash freeze the catch and smaller ones just kill them and keep them cool until they reach port. Keeping fish live on a boat just isn't practical.

Yea, the idea is a flying spotter drone with OWB Radar and some basic image recognition to find fish. The fact that it can find anything else is just a bonus. I know how sonar works, so please, everyone, stop explaining it to me. It doesn't work on a vehicle that's not touching the water. The surface acts as a sonar barrier.

Also, I've only been on board one commercial rod and reel type boat, and the hold did have water, and the fish were alive until they got taken off. I'll cue up a couple of episodes of Swords and see how they do it.

That idea is utter bollocks. If you want to sense something under the sea, you need to use Sonar. UWB simply will not cut it, no matter how you try to jimmy physics.

But by all means, go ahead and try it. I wanna see the look on the Star's face when they detain you and your airborne radar drone and you try to tell them it's for fishing.

I didn't say you can't have a water tank, but a mere refrigerated hold is easier to deal with and can probably store more fish for a given weight of filled hold - as far as I know the refirgerated hold is a more common design. I'd think the water tank system is more used for expsensive fishes you want to keep as fresh an intact as possible.

But an UWB radar won't go deep enough to spot most fishes - only those dwelling very close to the surface. What you might use if you're still going for a flyng 'spotter' could be a dipping sonar - a sonar haging at the end of a line that the drone can dip into the water. Anoter option coud be to use an hydrofoil based floating drone - go fast in hydrofoil mode and slow down once in position to get the sonar underwater.

You could also put a flotation mod on a C-D Dalmatian, but it won't leave you room for anything else. Than you can stick on your sonar, an underwater camera with a wildlife spotter sensor soft, and still have 4 sensor capacity left. So, your VTOL drone hovers over the water, activates it memory metals and forms a pontoon, plops down in the water and "sonars" your fish, or any incoming police vessels. Be creative - SeaDoo Bolts with LTA supplemented by Ford LEBD-1s with torpedo launchers, etc.

The boat has sonar. The drone is a Kull, which is fixed wing and doesn't hover, so dipped sonar won't work either. I can always add a couple of other drones with sonar to go out and search for fish.
Really the Kull should work fine, as it can spot the schools of feeders that the Tuna chase. Which will lead us to the Tuna.

quick question: are you looking for an excuse to have the kull in case the cops pull you over (figuratively speaking), or are you looking specifically to have your kull able to detect fish (and other underwater stuff)?

because if it's the former, well... it's not restricted in any way, and i think when you're at sea, using a resupply drone for resupply doesn't seem terribly ludicrous to me. you could also justify it by claiming you're using it to transport catches back to land to make sure your fish are as fresh as possible. or, better yet, both.

alternately, you could just give it sonar (in addition to a few other sensors), and adapt it to be able to land on water. frankly, you probably want to be able to land it on water anyways, no? so just land it, use the sonar to "check for fish" or whatever, and then take off from the water, move to a new location, check again, etc. there's your fish finder.

(on a side note, if you'd mentioned that the drone in question was a kull and specifically why you'd needed it, you could probably have gotten this kind of answer much earlier)

My question was, "does water have a barrier rating". I wasn't really looking for suggestions. I was looking for a yes or no. And if yes, what it is.
If not, maybe some idea of how much water is equal to a say a blast bunker (barrier rating 17, which a rating 4 uwb Radar will penetrate).

You could extrapolate based upon how far a bullet/Solid Ordinance that can penetrate a Blast bunker actually travels in water (Hint: Not very far).

The simple answer *was* given several times a while ago, so we moved on. (It was, 'radar penetrates zero distance'.)

Which is a silly answer that has nothing to do with reality or RAW. So I ignored it and clarified.
Radar penetrates water. Just not as well as sonar, which is effective over miles because of the longer waves. Sonar receivers will also work passively, because it uses audible frequencies. Radar only works when broadcasting, making it a bad thing for submarines which mostly try to remain hidden. That's why sonar is used rather than radar on subs. Not because radar doesn't work, but because sonar works better.

But I thought that maybe, with radar that would actually penetrate hardened concrete or air or anything else, it might penetrate to a good depth. But I don't have any idea how far, and I couldn't find a generic barrier rating for water. So I asked for help.
Having a low flying drone that could look a couple of hundred feet into the water, and couple that with target recognition and a good pilot program, could search a huge amount of space in a small amount of time, while other stuff was being done on board. Which would give me an excuse to have a small flying drone with a huge sensor package on my boat.

Bearclaw. Nothing you say, no prevarications you make, will enable the laws of physics to change. Water soaks up radar like a sponge.

If you want an answer, then fine, here it is:

Water has a Barrier rating of 2 per 2.51 centimeters of depth.

I'm just saying, all threads are inherently looking for suggestions. And discussion. They're our threads.

Prevarications? I'm not sure that word means what you think it means. You might want to back off that a little, cause it sounds exactly like a personal attack to me.


I keep on, because no one who actually knows anything I don't has answered.
Radar does go through water. Better than light, but not as well as sonar. In fact, I'd be willing to bet it goes through water a lot better than it goes through wood. I don't have a radar system to play with, so I'm not sure. And regular radar goes through wood 0. While UWB radar goes through wood just fine. So, I know UWB radar goes through water some, and probably a lot more than regular radar because of it's much wider wave, but still not as well as sonar. If no one knows the answer that's cool.
Feel free to discuss all you want. I'm not the king here. But I will also feel free to discuss, and expect to not be given any crap about it.

You don't have to have a radar yourself.

You can go look up the data. It's around.

And every single info source around will tell you that radar WILL NOT penetrate more than a few feet, unless you're using so much output power you'd be boiling the water in question.

NOBODY uses radar underwater. It simply doesn't work. The militaries of the world wouldn't have spent hundreds of millions of dollars in developing sophisticated sonar systems if they could just use radar.

That may not be the answer you were looking for, but it's the simple facts.

As for Shadowrun, the reason there's no rules on radar penetration of water is that the authors likely didn't think it'd even come up. The answer to the question is simply, "No, it won't work."



-k

Water, depending on the event, is stronger than concrete. Find the mythbusters episode where sniper rifle rounds essentially shatter on impact and have no effective energy in less than 3ft of water.

Concrete is only twice as dense and both are essentially incompressible materials but water actually absorbs less energy because it doesn't shatter.

From a structural standpoint, in WWII there was a project to build disposable aircraft carriers out of ice & wood pulp. A test model survived in Canada for years. The wood pulp was to remove the brittleness; concrete is also brittle, hence the need for steel reinforcements.

So basically, water should have a barrier rating only slightly less than concrete by thickness.

Oh, and I'm a licensed (retired/inactive) civil engineer. I know a few things about concrete and water.

or, you could have the exact same systems, except swap out one thing (not the radar) for sonar that it can use by simply landing every minute or so. sensors such as radar are commonplace on drones, because it is generally considered a desirable thing for your drone to not crash into everything and everything while doing drone stuff.

you can even justify upgrading the sensor capacity, because that also increases range. my explanation gives you a perfectly plausible reason to have sensors on a flying resupply drone; transport fresh fish to market instead of waiting for the boat to return, transport any needed supplies to the boat instead of having to go back to shore. it has sensors because when it isn't running errands like buying your groceries for the day, it's trying to find fish for you to catch.

just because an answer is not the exact one you wanted to hear in the exact same words, doesn't mean that it isn't a viable answer. now unless there is some specific reason you need to have ultra wide band radar (which is the only non-standard sensor you've mentioned wanting), you've got a very easy solution that works. you've even got a reason to have two or more if you want (so that you can continue fish-finding even while one of them is running errands).

I have poke a bit around the web looking for numbers, including a thesis about usib Therahertz-range radar to monitor chemical reactions - which would end up spot on on within the range used in and UWB radar. And in this thesis, the reseached warned of the need to limit the thickness to be penetrated because therahertz-waves are absorbed really fast (in a similar fashion as a microwave oven).

I don't know the exact mecanisms involved, but liquid water is extremely difficult to pentrate with electromagnetic waves - even agmma rays have a hard time punching though and the buggers are extremely energetic - the classic image of a reseach reactor shining a pretty cherenkov effect is a god example of that.

The rate of absoption varies with teh wavelength, with the less bad options bieng visible light in the blue-green spectrum (say 50 to 100 yards and very senstive to how clar thh water is) and very long wave radio; used to cotact underwater submarines. Which compeltely sucks for detecticion because the wavelgnth is so long you can't detect somehtign smaller that the ocean floor.

Different materials behave in different fashion toward radio wave -a good example would be a microwave oven : ceramics and glass let the waves moves though, water soaks it like a sponge and the thinnest sheet of metals sends it bouncing back.

Assuming I am remembering correctly, the issue is actually the oscillations of water. It's similar to why a vibration detector can more accurately pick up sound off a vibrating brick wall than through water, and is why water stops bullets better than concrete of equal mass. The water cavitates on impact, creating it's own vibrations and wavelengths, which are MUCH BIGGER and slower than ones through air. They also go further. This is why sound carries better in water.

However, the trick then is distortion. RADAR distorts through water much more severely than water because of it's higher frequency. This is a similar principle to why the bullet stops, actually, because the path distorts quickly, causing loss of momentum through directional changes in water movement and pressure, which has much more drag and weight than air. Basically, RADAR doesn't work in water because what gets reflected back is inconsistent garbage sound.

sourcelink


And from the document previously linked:
The reason [why radar is not used to find subs] is mainly because radar has a harder time penetrating large volumes of water. Contacts made by submarines are often dozens of miles away, and radar would have to be EXTREMELY powerful to reach that far in water, while sound (a mechanical wave) can make it that far.

GPR is another matter, but keep this in mind: GPR can be made to go further with LOWER frequency (coming closer to sonar in wavelength) but the detail of the image (which you'd need to find fish smaller than whales) goes to shit. So here is what I think for fish.

Ground Penetrating Radar comes closest to the shadowrun rating 4 radar (based on your comparison for the bunker) and so I'd use it as a comparison. It is known to inaccurately image freshwater lakes. Assuming shadowruns version is futuristic-ally better (GPR still sucks at penetrating water) I would say that it would have a barrier rating of 1 per 2-5 foot depth of standing fresh water.

GPR works less accurately the more electrically conductive a material is, in addition to attenuation problems. Salt water is MORE electrically conductive than fresh (lemme head arguments off at the past here: look it up first if you disagree) and GPR doesn't penetrate seawater with nearly the same depth as fresh. I would suggest a barrier rating for salt water along the lines of the numbers given previously, maybe less: 4 per 2-5 foot depth of seawater. So a building surrounded by a saltwater aquarium, with grounded water tanks, would be MUCH harder to penetrate than your previously mentioned bunker, and this is in keeping with current technical norms.

Since software correction plays a big part, GMs make want to use programming as well, depending of your depth of detail

sourcelink


TL:DR version - 1 per 2-5 feet fresh water. 4 per 2-5 feet salt water, for finding fish smaller than 50 pounds. Submarine sized images would allow for further depth, obviously.

Which means that pretty much all radar is going to be useless for deeper than 10-15 or so feet of seawater.

Which mirrors real life. Nicely done.





-k

I dont see the problem.

1. Get KULL
2. Add Winch
3. Add Sonar

Sonar is put on the winch
Kull goes low altitude flying and dips the sonar 20-50 meters below the surface while flying at 50-80 meters above the water.

It doesnt HAVE to go at maximum speed, just let the onboard pilot keep it above stall speed.