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Cell Towers Can Double as Cheap Radar Systems for Ports and Harbors (2014)

(spectrum.ieee.org)
137 points transpute | 2 comments | 29 Jun 25 21:48 UTC | HN request time: 0.437s | source
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transpute ◴[29 Jun 25 23:52 UTC] No.44417727[source]▶
More coverage of RF sensing, including laptops/phones with radios+NPU to sense their human:

2025, "Espargos: ESP32-based WiFi sensing array", 30 comments, https://news.ycombinator.com/item?id=43079023

2024, "How Wi-Fi sensing became usable to track people's movements", https://www.technologyreview.com/2024/02/27/1088154/wifi-sen...

2023, "What Is mmWave Radar?: Everything You Need to Know About FMCW", 30 comments, https://news.ycombinator.com/item?id=35312351

2022, "mmWave radar, you won't see it coming", 180 comments, https://news.ycombinator.com/item?id=30172647

2021, "The next big Wi-Fi standard is for sensing, not communication", 200 comments, https://news.ycombinator.com/item?id=29901587

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Animats ◴[30 Jun 25 03:37 UTC] No.44419092[source]▶
Right. The longer range versions of multistatic radar are used to detect stealth aircraft.[1][2] All that careful stealth geometry to minimize direct reflections doesn't help much when the emitters and receivers are in different locations.

[1] https://www.presstv.ir/Detail/2024/11/18/737423/guardians-of...

[2] https://www.yiminzhang.com/pdf/radar13_passive.pdf

replies(3): >>44420317 #>>44421093 #>>44424653 #
4gotunameagain ◴[30 Jun 25 07:01 UTC] No.44420317[source]▶
No but the highly classified radar absorbing compounds that stealth aircraft are wrapped in definitely help :)
replies(2): >>44420349 #>>44420563 #
1. kuschku ◴[30 Jun 25 07:07 UTC] No.44420349[source]▶
How does it help if you're passing between transmitter and receiver?

(either directly, or by bouncing a radar signal off the ionosphere and receiving it again)

You should still show up as a shadow?

replies(1): >>44420503 #
2. ruined ◴[30 Jun 25 07:36 UTC] No.44420503[source]▶
direct is practically useless, because that's point-to-point. lighting up the ionosphere that way seems like the hardest case scenario, requiring a very powerful transmitter, somehow ignored by sensitive high-resolution scanning over a large area of sky. and you'd be disrupted by other occluding objects like water vapor

there is precedent https://en.m.wikipedia.org/wiki/Over-the-horizon_radar but it seems like a limiting factor is suitable frequencies and resolution