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#61
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Defense against UAV's
Jack Linthicum wrote:
[snip] I think that a spread spectrum burst type transmission can be intercepted and given a rough bearing. The money to do this is miniscule in comparison with making Trident missiles into hand grenades. The command post does not move between transmissions. Spread spectrum/frequency hopping systems return to previous frequencies every few seconds. Just use several bursts to home in on the transmitter. Andrew Swallow |
#62
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Defense against UAV's
Andrew Swallow wrote: Jack Linthicum wrote: [snip] I think that a spread spectrum burst type transmission can be intercepted and given a rough bearing. The money to do this is miniscule in comparison with making Trident missiles into hand grenades. The command post does not move between transmissions. Spread spectrum/frequency hopping systems return to previous frequencies every few seconds. Just use several bursts to home in on the transmitter. ?? You transmit only when you want to issue new command to the swarm, not to control every little thing. You can have minutes without transmission, then 10ms transmission, followed by another long silence. And you can also have plenty of cheap decoy trasmitters, just to make it easier to intercept ... something. ;-) Andrew Swallow |
#63
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Defense against UAV's
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#64
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Defense against UAV's
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#65
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Defense against UAV's
Mark Borgerson wrote:
In article , says... Jack Linthicum wrote: [snip] I think that a spread spectrum burst type transmission can be intercepted and given a rough bearing. The money to do this is miniscule in comparison with making Trident missiles into hand grenades. The command post does not move between transmissions. Spread spectrum/frequency hopping systems return to previous frequencies every few seconds. Just use several bursts to home in on the transmitter. Why are you assuming that the command post does not move? I see no reason that a mobile command post and multiple mobile transmitters could not be used. This comes down to the definition of mobile. If the command post stays in the same place for half an hour it is static. A constantly moving command post would need a vehicle the size of a bus to hold the operators and long range transmitters, possible but hard to camouflage. Spread spectrum and frequency hopping systems do use a finite number of frequencies---but the sequence of freqencies used may not repeat for many hours. That leaves you with a broadband collection problem and having to sort out multiple emitters on the same bandwidth with different hopping schedules. I suspect that is a problem handled offline and after-the-fact, and not in real time. However, the technology has probably advanced a bit in the 30 years I've been out of the sigint world. ;-) If we are trying to destroy the command post we do not need to receive the entire message we can simply wait until that frequency is reused by that transmitter. If the equipment is hopping over 100 frequencies it should be back within the next 200 transmissions. The computers will need programming to treat transmissions from two widely separated locations as two targets. Home in on them one at a time. Andrew Swallow |
#66
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Defense against UAV's
"Keith W" wrote in message
... wrote in message oups.com... [ SNIP ] A UAV with realtime video image recognition and IR sensors is unlikely to be especially cheap Realtime video image recognition needs a source of video (probably a wide-angle search camera + narrow angle scope with some decent magnification for examining the suspicios contacts), Problem 1 ) You have to process them to decide if they are suspicious a decent CPU to do the number crunching and a software to do the analysis. The first two items are not particularly expensive. The software might take real pains to develop, but afterwards the copies are free. Understatement of the year [ SNIP ] If he can show the image processing and recognition problem to be easy, his soon-to-be net worth will be more than that of Bill Gates. In fact, he'll hire Billy just to supervise the programming staff to write the queuing software for his executive bathroom. Despite humongous amounts of research being done over many decades, general computer vision remains an intractable problem. To illustrate, it may be impossible for a vertical photograph (satellite) to differentiate between a parking lot surrounded by a board fence and with a few cars parked on it, and a large building with a flat roof and large roof vents, both with roads nearby and under conditions of shadowing. Now, in this case we'd certainly have a rules base codifying the knowledge. But even restricting the problem to that of finding ships in the open ocean, it's still not that simple. At a typical distance and altitude, a lot of those ship lines are actually curves, so your algorithms need to recognize smooth curves as part of a ship definition. Hmmmm, what else at sea is often a fairly smooth curve? I have a photo (8 1/2 by 11") of most of 4th MEB at sea, either 1990 or 1991. Fourteen vessels (LSTs, LPDs, LSDs, LPHs, one LHA, and a hospital ship - no UNREP ships) are depicted. Going off the length of the LHA (shown at a significant oblique), my estimate (very rough) is that the formation is 5-6 km across and perhaps 3 km deep. Even compressed like this - it's a formation in time of hostilities that surely makes captains nervous - it's still a collection with lots and lots of empty space. The colour contrast and the wakes, the very calm conditions and excellent vizibility (light haze) will at least allow a decent software to identify the ships as ships. Leaving aside the hospital ship, I don't see that classifying most of the vessels in the photograph would be anything other than a [very] difficult recognition problem. A human can do it quickly, especially if cued with the knowledge that everything is a USN gator, but it would be a pretty expensive program that reliably typed each target. One wonders too if the supposedly small and cheap UAV with the purportedly inexpensive but sophisticated image recognition system is also fixing the precise 3-D attitude of the airframe and hence the camera in order to allow for estimating sizes of the objects in the picture, and _their_ attitude. Forget relying on the horizon - in my picture you can barely make it out because of haze. And it would have to be really precise data in order to get good dimensional info. What if you can't even see the wake, for one of several reasons? I'll give the program three stars if it even correctly figures out what end of the ship is which. Now let's suppose that I am somewhat harsh in my analysis. Let's say that a relatively coarse resolution picture and a basic analysis alerts the software to "blobs of interest", and then the vehicle + camera is commanded to do what it needs to do to get high-res images, and a better routine analyzes these. Given some near optimal pictures - nearly side-on to the vessel - you'd have something to work with. But in order to gauge size, you'd need to be at some moderate altitude to have good geometry, under which conditions superstructure begins to blend into the rest of the mass, not be outlined against sky. In any case, with a large, detailed image of the target, you now encounter other recognition problems e.g what details do I ignore? It is not a simple problem. AHS |
#67
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Defense against UAV's
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#68
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Defense against UAV's
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#70
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Defense against UAV's
"Keith W" wrote:
:"ray o'hara" wrote in message ... : : laser guided weapons gave a tendency to attack the sun. you only see the : good ones on tv, not all the misses. : :Utter ********, the laser sensors look for reflected light at :specific frequencies Ray is, as usual, being an idiot. Not only reflected light at specific frequencies, but with a specific code. : rocks eated by the sun. reflections off of pools of water or streams can : also distract them. : :You seem not to understand the difference between IR and laser sensors He's also the better part of a century behind when it comes to IR, since IIR weapons (what he seems to be referring to) have very little problem with practically everything he mentions. He apparently thinks laser weapons home on heat. Hell, even IR strike weapons don't do that! -- "Ignorance is preferable to error, and he is less remote from the truth who believes nothing than he who believes what is wrong." -- Thomas Jefferson |
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