# Can radar detect a person-sized object?
**URL:** https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903
**Category:** Factual Questions
**Created:** [October 8, 2016, 2:56am UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903 "2016-10-08T02:56:30Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@Love\_Rhombus](https://boards.straightdope.com/u/Love_Rhombus)
#### Post date: [October 8, 2016, 2:56am UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903/1 "2016-10-08T02:56:30Z")
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?
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### Author:  [@leftfield6](https://boards.straightdope.com/u/leftfield6)
#### Post date: [October 8, 2016, 2:58am UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903/2 "2016-10-08T02:58:33Z")
Ga State Police had no problem detecting me on a motorcycle, sad to say.:rolleyes:
I know thats not the radar you are referring to, but there ya go.
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### Author:  [@The\_Niply\_Elder](https://boards.straightdope.com/u/The_Niply_Elder)
#### Post date: [October 8, 2016, 3:02am UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903/3 "2016-10-08T03:02:03Z")
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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### Author:  [@Love\_Rhombus](https://boards.straightdope.com/u/Love_Rhombus)
#### Post date: [October 8, 2016, 3:04am UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903/4 "2016-10-08T03:04:43Z")
Hmm. Am I thinking of something other than radar?
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### Author:  [@running\_coach](https://boards.straightdope.com/u/running_coach)
#### Post date: [October 8, 2016, 3:11am UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903/5 "2016-10-08T03:11:26Z")
> [@Love\_Rhombus](#):
>
> Hmm. Am I thinking of something other than radar?
Photons? 😃
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### Author:  [@scr4](https://boards.straightdope.com/u/scr4)
#### Post date: [October 8, 2016, 3:22am UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903/6 "2016-10-08T03:22:02Z")
> [@The\_Niply\_Elder](#):
>
> 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](https://en.wikipedia.org/wiki/Radar_cross-section#Measurement) 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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### Author:  [@Great\_Antibob](https://boards.straightdope.com/u/Great_Antibob)
#### Post date: [October 8, 2016, 3:26am UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903/7 "2016-10-08T03:26:00Z")
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.
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### Author:  [@mixdenny](https://boards.straightdope.com/u/mixdenny)
#### Post date: [October 8, 2016, 5:54am UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903/8 "2016-10-08T05:54:01Z")
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
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### Author:  [@AK84](https://boards.straightdope.com/u/AK84)
#### Post date: [October 8, 2016, 6:39am UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903/9 "2016-10-08T06:39:08Z")
Ground Survialluance Radar
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### Author:  [@MichaelEmouse](https://boards.straightdope.com/u/MichaelEmouse)
#### Post date: [October 8, 2016, 7:04am UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903/10 "2016-10-08T07:04:52Z")
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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### Author:  [@Marvin\_the\_Martian](https://boards.straightdope.com/u/Marvin_the_Martian)
#### Post date: [October 8, 2016, 9:21pm UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903/11 "2016-10-08T21:21:17Z")
> [@Great\_Antibob](#):
>
> 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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### Author:  [@Melbourne](https://boards.straightdope.com/u/Melbourne)
#### Post date: [October 9, 2016, 3:34am UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903/12 "2016-10-09T03:34:45Z")
> [@AK84](#):
>
> 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.
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### Author:  [@Spiderman](https://boards.straightdope.com/u/Spiderman)
#### Post date: [October 9, 2016, 4:11am UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903/13 "2016-10-09T04:11:15Z")
Ever watch a baseball game, or throw one at the boardwalk/a carnival? How do you thing they know how fast it was thrown?
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### Author:  [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)
#### Post date: [October 9, 2016, 6:05am UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903/14 "2016-10-09T06:05:06Z")
> [@MichaelEmouse](#):
>
> 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](http://yaffa-cdn.s3.amazonaws.com/mysailing/images/dmImage/StandardImage/radar-reflector_mid.gif) paints very well on radar, much better than the yacht it gets attached to.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [October 9, 2016, 11:46am UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903/15 "2016-10-09T11:46:31Z")
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.
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### Author:  [@mbh](https://boards.straightdope.com/u/mbh)
#### Post date: [October 9, 2016, 12:08pm UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903/16 "2016-10-09T12:08:13Z")
If the Galactic Overlord doesn’t beat you to it.
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### Author:  [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)
#### Post date: [October 9, 2016, 1:31pm UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903/17 "2016-10-09T13:31:57Z")
[Radar detects people through walls](https://www.ll.mit.edu/news/thruwallradar.html).
So yes, it can; if it’s designed for the job at least.
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### Author:  [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)
#### Post date: [October 9, 2016, 2:29pm UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903/18 "2016-10-09T14:29:50Z")
> [@scr4](#):
>
> 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](https://en.wikipedia.org/wiki/Radar_cross-section#Measurement) 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.
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### Author:  [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)
#### Post date: [October 9, 2016, 2:32pm UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903/19 "2016-10-09T14:32:46Z")
> [@Spiderman](#):
>
> 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?
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### Author:  [@dtilque](https://boards.straightdope.com/u/dtilque)
#### Post date: [October 9, 2016, 10:19pm UTC](https://boards.straightdope.com/t/can-radar-detect-a-person-sized-object/767903/20 "2016-10-09T22:19:17Z")
> [@leftfield6](#):
>
> Ga State Police had no problem detecting me on a motorcycle, sad to say.:rolleyes:
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.
> [@Great\_Antibob](#):
>
> 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.
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