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Old 10-07-2016, 10:56 PM
Love Rhombus Love Rhombus is offline
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Can radar detect a person-sized object?

To use a movie example, could military anti-aircraft radar "see" Superman? Or is there another type of detection they would use for something that size?
  #2  
Old 10-07-2016, 10:58 PM
leftfield6 leftfield6 is offline
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Ga State Police had no problem detecting me on a motorcycle, sad to say.

I know thats not the radar you are referring to, but there ya go.
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Old 10-07-2016, 11:02 PM
The Niply Elder The Niply Elder is offline
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Yes you can detect objects as small as water droplets and ice particles (aka rain and hail). You may have seen such detections plotted on maps by weather forecast services.
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Old 10-07-2016, 11:04 PM
Love Rhombus Love Rhombus is offline
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Hmm. Am I thinking of something other than radar?
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Old 10-07-2016, 11:11 PM
running coach running coach is online now
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Originally Posted by Love Rhombus View Post
Hmm. Am I thinking of something other than radar?
Photons?
  #6  
Old 10-07-2016, 11:22 PM
scr4 scr4 is offline
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Originally Posted by The Niply Elder View Post
Yes you can detect objects as small as water droplets and ice particles (aka rain and hail). You may have seen such detections plotted on maps by weather forecast services.
That's like saying your eye can detect a 1-micron particle because you can see cigarette smoke. Radar cannot detect individual droplets of water. It can detect clouds made up of water droplets, but that doesn't mean it can pick out individual droplets.

Anyway, Wikipedia says a human has a radar cross-section of about 1 m^2, while a "small combat aircraft" has 2-3 times that much. So I would think any radar system designed to reliably detect small combat aircraft will detect a human.
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Old 10-07-2016, 11:26 PM
Great Antibob Great Antibob is offline
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We have radar that can detect birds (at least in small clumps), so, yes, person-sized objects can be detected by radar.

But one problem is identification. Think stealth aircraft. Stealth aircraft reduce the signal that radar systems get. They aren't invisible to radar but rather just really difficult for radar systems to properly detect and identify.

If your radar is sensitive enough to pick up a person, it's picking up everything. It becomes a real needle in a haystack problem. Is that Superman? Or a plane? Or a flock of birds? Or just a small cloud? Now, if that cloud is moving at Mach 15, maybe you have something.

Last edited by Great Antibob; 10-07-2016 at 11:26 PM.
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Old 10-08-2016, 01:54 AM
mixdenny mixdenny is offline
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Ballistic radar at military test ranges can not only track individual rifle bullets, they can measure the minute changes in velocity caused by the bullets' wobble. The usual smooth curve of the trajectory appears as a slight sine wave. The amplitude of the sine wave is the change in apparent velocity of the nose of the bullet precessing around a center. The frequency measures the bullet's spin rate. And this was a long time ago, at least 20 years.

Dennis
  #9  
Old 10-08-2016, 02:39 AM
AK84 AK84 is online now
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Ground Survialluance Radar
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Old 10-08-2016, 03:04 AM
MichaelEmouse MichaelEmouse is offline
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Isn't the reflection highly dependent on what the object is made of? For example, a person made of flesh and bones would be far less radar reflective than a person of the same size made of metal, right?

Does the size of common radar wavelengths make person-size objects reflect chiefly specular reflections?
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Old 10-08-2016, 05:21 PM
Marvin the Martian Marvin the Martian is offline
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Quote:
Originally Posted by Great Antibob View Post
If your radar is sensitive enough to pick up a person, it's picking up everything. It becomes a real needle in a haystack problem. Is that Superman? Or a plane? Or a flock of birds? Or just a small cloud? Now, if that cloud is moving at Mach 15, maybe you have something.
You got it backwards. The correct order is, "It's a bird! It's a plane! it's Superman!"

(Or some of us prefer, "It's a bird! It's a plane! It's a frog! A frog?!?")
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Old 10-08-2016, 11:34 PM
Melbourne Melbourne is offline
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Ground Survialluance Radar
When the Brit's were introducing German-Bomber-Detection radar during WWII, one of the radar huts participated in local training excercise that pitted the rader techs (desk soldiers) against the defense guards (the real soldiers). Naturally (radiation safety being an unknown concern) they redirected their radar test & development equipment at ground level to detect the attack forces creaping towards them in the night -- leading to a very gratifying win for the desk soldiers.
  #13  
Old 10-09-2016, 12:11 AM
Spiderman Spiderman is online now
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Ever watch a baseball game, or throw one at the boardwalk/a carnival? How do you thing they know how fast it was thrown?
  #14  
Old 10-09-2016, 02:05 AM
Richard Pearse Richard Pearse is offline
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Quote:
Originally Posted by MichaelEmouse View Post
Isn't the reflection highly dependent on what the object is made of? For example, a person made of flesh and bones would be far less radar reflective than a person of the same size made of metal, right?

Does the size of common radar wavelengths make person-size objects reflect chiefly specular reflections?
Materials make a big difference, metal is much better than wood for example. Also the shape is very important. Lots of right angles will give a good reflection. One of these paints very well on radar, much better than the yacht it gets attached to.
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Old 10-09-2016, 07:46 AM
Chronos Chronos is offline
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You can also make one of those out of discarded foil, and attach it to your freely-orbiting cargo of bicycles, in case you get a chance to come back for it later.
  #16  
Old 10-09-2016, 08:08 AM
mbh mbh is online now
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If the Galactic Overlord doesn't beat you to it.
  #17  
Old 10-09-2016, 09:31 AM
Der Trihs Der Trihs is offline
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Radar detects people through walls.

So yes, it can; if it's designed for the job at least.
  #18  
Old 10-09-2016, 10:29 AM
Leo Bloom Leo Bloom is offline
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Originally Posted by scr4 View Post
That's like saying your eye can detect a 1-micron particle because you can see cigarette smoke. Radar cannot detect individual droplets of water. It can detect clouds made up of water droplets, but that doesn't mean it can pick out individual droplets.

Anyway, Wikipedia says a human has a radar cross-section of about 1 m^2, while a "small combat aircraft" has 2-3 times that much. So I would think any radar system designed to reliably detect small combat aircraft will detect a human.
Good cite.
  #19  
Old 10-09-2016, 10:32 AM
Leo Bloom Leo Bloom is offline
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Originally Posted by Spiderman View Post
Ever watch a baseball game, or throw one at the boardwalk/a carnival? How do you thing they know how fast it was thrown?
This is a particular case of detection, as mentioned in the first post. How do think that was radar? And what about the human standing still?
  #20  
Old 10-09-2016, 06:19 PM
dtilque dtilque is online now
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Originally Posted by leftfield6 View Post
Ga State Police had no problem detecting me on a motorcycle, sad to say.
In my area, the sheriff's department will put up temporary radar units in areas where people complain about speeders. They don't give out ticket, just a display to the drivers of what speed they're going and sometimes a "slow down" message, if it's too fast. I've gotten readouts from those while on my bicycle, although I have to get fairly close to get one. Haven't gotten a "slow down" message yet. My bicycle has a very small fraction of the metal your motorcycle has.

Quote:
Originally Posted by Great Antibob View Post
If your radar is sensitive enough to pick up a person, it's picking up everything. It becomes a real needle in a haystack problem. Is that Superman? Or a plane? Or a flock of birds? Or just a small cloud? Now, if that cloud is moving at Mach 15, maybe you have something.
Picking up everything is a significant problem with radar and has been almost since the beginning. If you ever see the raw return of a search radar, you'll see there's so much returned signal from the first few miles that it's useless. So what radars have is a ground clutter suppression circuit. Any returned signal within a certain distance and with a doppler shift less than a certain low amount has its signal suppressed on the radar display. On early radars, they had to have an electronic circuit that would do this, but I imagine modern ones do it in software.
  #21  
Old 10-09-2016, 07:22 PM
joema joema is offline
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Quote:
Originally Posted by Leo Bloom View Post
This is a particular case of detection, as mentioned in the first post. How do think that was radar? And what about the human standing still?
Not sure what you mean, but the radar run obviously detects the baseball. If a human being was fired out of a canon it could detect that.

There are many different types of radar, each with unique capabilities.

Decades ago, even older radars could detect a single mortar shell: https://en.wikipedia.org/wiki/AN/TPQ...refinder_radar

Guided only by radar, Phalanx and the land-based C-RAM have not only detected but intercepted many artillery and mortar shells. This requires a 3D spatial solution within a few inches: https://en.wikipedia.org/wiki/Counte...ry,_and_Mortar

The Israeli Iron Dome radar system has intercepted many mortar shells and Qassam rockets which are about man-sized. These are not only detected but the missile is radar-guided to an intercept in 3D space. Admittedly there is a handoff in the terminal phase to on-board radar, but Patriot PAC-2 has intercepted small artillary rockets using only ground-based radar: https://youtu.be/TwyImK6KCTc?t=25

Millimeter-wave imaging radar can not only detect people but small objects they are carrying: http://spearpoint-shop.myshopify.com...ation-handheld

So it depends on the radar system and what it's designed to achieve. While NOAA's WSR-88D weather radar can detect swarms of bugs and birds, as already stated it cannot detect an individual bird, at least with the current processing system.

The Navy's SPY-1A phased array Aegis radar system has roughly the same angular resolution as the WSR-88D but obviously has processing designed to detect smaller objects, probably from doppler discrimination. Your point about a static object may be valid -- if superman was hovering, not moving in three dimensions relative to the radar, maybe he couldn't be detected by something like SPY-1A.

SPY-1A (in NWRT test bed) vs WSR-88D for weather observation: http://images.slideplayer.com/19/582...s/slide_11.jpg

OTOH Ku-band space tracking radars can detect objects less than 2 cm diameter at 1,000 miles: https://en.wikipedia.org/wiki/TIRA_(System)
  #22  
Old 10-09-2016, 08:12 PM
Leo Bloom Leo Bloom is offline
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My point was clocking a moving object is not sufficient and exclusionary evidence of radar, and neither does arriving at the rate of change of motion of the object, which is one step removed from OP.

You can use Doppler acoustics for the same job in many circumstances.
  #23  
Old 10-10-2016, 09:08 AM
Boyo Jim Boyo Jim is offline
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My car can detect people walking toward it from the rear quarters. They call it "rear cross-traffic alert. The documentation says it's "radar", but who knows if they're using the correct term? All I can tell for sure is that the people who set off the alert are not within the viewing field of the backup cam.
  #24  
Old 10-10-2016, 09:21 AM
Declan Declan is offline
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Quote:
Originally Posted by Boyo Jim View Post
My car can detect people walking toward it from the rear quarters. They call it "rear cross-traffic alert. The documentation says it's "radar", but who knows if they're using the correct term? All I can tell for sure is that the people who set off the alert are not within the viewing field of the backup cam.
My escape has infra red beams that project out to the rear in an arc, anyone or thing that breaks the beam sounds the audible alert. For your car to actually have some sort of radar, I would expect that your documentation should show some sort of FCC side doc's on how much milimeter wave radar that its putting out, and any kind of radiation warnings.

Declan
  #25  
Old 10-10-2016, 09:25 AM
Boyo Jim Boyo Jim is offline
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Quote:
Originally Posted by Declan View Post
My escape has infra red beams that project out to the rear in an arc, anyone or thing that breaks the beam sounds the audible alert. For your car to actually have some sort of radar, I would expect that your documentation should show some sort of FCC side doc's on how much milimeter wave radar that its putting out, and any kind of radiation warnings.

Declan
I would assume that if it's emitting infra red, then it IS radar, which is just another bit of the EM spectrum.
  #26  
Old 10-10-2016, 09:49 AM
Chronos Chronos is offline
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They're both parts of the EM spectrum, but radar specifically refers to devices using one particular portion of the spectrum. An IR-based system would probably be lidar.
  #27  
Old 10-10-2016, 12:58 PM
Leo Bloom Leo Bloom is offline
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Originally Posted by Chronos View Post
They're both parts of the EM spectrum, but radar specifically refers to devices using one particular portion of the spectrum. An IR-based system would probably be lidar.
This reminds me of the word "acoustics" as a general phenomenon of physical conduction and the one in a medium of air.

And don't get me started with "phonons" as their constituent.

Last edited by Leo Bloom; 10-10-2016 at 01:00 PM.
  #28  
Old 10-10-2016, 01:04 PM
Leo Bloom Leo Bloom is offline
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Radar Secret Service, 1950, hunt for stolen U-238.

Complete movie (MST3K: https://youtu.be/eQT66quwTjE
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