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On a sunny day (Sun, 31 Dec 2006 09:56:06 +0100) it happened Helmut Wabnig
<.... .-- .- -... -. .. --. @ .- --- -. DOT .- -> wrote in
<7fuep2pnpmrbkjck7c1m193l025lej6ijg@xxxxxxx>:
>On 30 Dec 2006 19:51:21 -0800, "Peter Divos" <pdivos@xxxxxxxxx> wrote:
>
>>Hi,
>>
>>I heard there are some types of radar which operate passively, this
>>means, they dont send any signal and dont wait for the echo, but they
>>get some random electromagnetic waves from the air which are reflected
>>on objects as well and it is possible get some image in exchange of
>>some computation.
>>I also heard of a swiss company who are using the same principle but in
>>geology, seismology, oil exploration. They dont produce any signal
>>(like explosion under the surface) but instead use very sensitive
>>detectors and catch the random seismic noise from the earth which
>>reflects as well and get the image based on this.
>>
>>So. I am interested in the mathematical and algorithmical part of the
>>topic. Does anyone know any good references? Like keywords or book
>>titles.
>>
>>Many thanks
>>Peter
>need two or more antennas. Two ears, and listen.
>Localizing lighning flashes is an application
>http://www.aldis.at/
>
>The theory is basically ident, if you send a signal and wait for the
>reflections, or just listen to what is coming along, acoustically or
>electromagnetic.
> en.wikipedia.org/wiki/Passive_radar">http://en.wikipedia.org/wiki/Passive_radar
In fact the eyes are a nice passive radar, using available electromagnetic
sources to create a 3D picture.
The subject is 'lens'.
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