Scanners?

I'd like to play a little science fiction hide and seek with you. Say there is a guy on a planet who does not want to be localised and one, who wants to find him. ... In a kind of military science fiction setting.

What kind of "scanners" could be used? And how would one avoid or at least jam them?

Obviously, there are electromagnetic rays to be scanned. In the most primitive case, this means: Visible light -> Optic sensors.
How to avoid this? Clothes of the right color and lot's of distance could help, unless the sensor is really advanced. Something blocking the line of sight would be the only way to be sure. If necessary a very bright flash could blind them for a short time - or could that fail for more advanced sensors?

Next there is the infrared radiation. This aplication is obviously diffrent from space combat: It's looking for a person with body temprature but it's also on a planet with some ambience temperature.
Avoidable by wearing an isolated suit ... untill it overheats inside. A cooling system and a heat sink may allow a long time of "thermo-invisibility". Rivers and the like could be used to dissipate the heat without the scanners at land noticing.

And maybe: Radioscans. In case the person to find is comunicating via radio, this can be triangulated easily.
Easy solution to avoid this would be not to use radio. But besides this I guess directed radio beams could work, too, if you have line of sight to your teammates' satelite dishes.
How well would "limited signal strength" work, if the opposing site has the same technology level but much more space? If the teammate with his personal radio unit is meant to receive the transmission 500 meters away, how far away from the enemie's building-sized antennas would you have to be, so that they can't pinpoint your signal?


Are there other electromagnetic frequencies interesting?
What other ways of scanning are there?


Magnetic-field-Scanners: aka: Metal detectors. There are two thinks possible here: One Scanner that emits an own magnetic field and measures chances in that, or one, that uses the planet's magnetic field.
I think this has a lot of potential, besides not wearing any metal, I see no way to avoid the detection.
How would it best be jammed? Could an "Ionizing radiation gun" ionize enought air (which to my understanding of physics should have the fieldscanner fire, too), or would you have to blow chaff-greanates up everywhere around yourself, to hide your exact location?
And important: How effective would this be in a common house, are cables and pipes in the walls enough to prevent this scanner or would it have to be completely metal-plated walls?


What else? I can think of a neutrino-scanner, in case the target of the search uses a nuclear powered armor. Is there a compact way to stop neutrinos - except for neutronium plate which might be a little to far future?

Finally - in common so called (not here) science fiction TV series, you often hear of "lifeform-detectors", "bio scanners" or something like that, that seam to penetrate anything and work over huge distances. Did anyone ever think of a way they could really work, or is it just magic?

dclary said:

You forgot motion detectors, radar, sonar, spatial recognition systems (computer knows what a "man" looks like and identifies any object it sees against its database of known objects), and that's just using today's technology.

Click to expand...

Motion detection and spatial recognition are the AIs behind the Sensors, I'm looking for. But of course, sound based systems are something I forgot. And among sound based systems, Sonar is standing out, as a solid system to see unobcured targets, when vision is not possible (darkness). Optic sensors would have a much better resolution and are less effected by background noises (changing lightnings in case of the optical thing).

Of course, since it is an active system anyway, you could just as easy use strong searchlights. ... Then again the target could use smoke and you are back using sonic sensors which could be jammed by white noise screamers ...


Radar ... *reads Wikipedia* ... Yes, among the emectromagnetic radiation Scanners, active systems using radar- and microwaves sould not be forgotten. It says that by measuring the diffrence in wavelength, the reflecting surface's speed can be measured. ... I guess that works for aircrafts but I guess it should mot work for a single person.
Besides this it is good at realising density diffrences. On the negative side, this meens that a human mostly water filled body in heavy rain will be difficult to find (at high distances), on the positive side, a dense armor in a forest (not so dense wood) might detect earlier then visual sensors.
Counter-measure: Radar absorbing materials. Also, jamming is the easies here, just shooting broadband radio/microwave rays at the Radar.


With sonic sensors, seismic sensors come into my mind, too. However, this is more the tech for thievery-stuff, I don't think, this would be realiseable to secure fields and forests, would it? Or to ask that way: Foodsteps of say a 100 kg humanoid in average earth could be recognised by seismic sensors how far away? I wouldn't expect is to be more then a few meters (and only a few more with reasonable future tech).