Post AZLbMLB1UTcYBVFxQm by Paxxi@hachyderm.io
(DIR) More posts by Paxxi@hachyderm.io
(DIR) Post #AZLQ4RapnUJPNNaq48 by mjg59@nondeterministic.computer
2023-09-02T03:45:56Z
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Say I have line of sight to a river and would like to monitor how its height is changing over time, is there anything that'll just bounce some sort of signal off it to tell me distance?
(DIR) Post #AZLQkBqajKf0hgrxvk by Viss@mastodon.social
2023-09-02T03:53:22Z
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@mjg59 i suppose if you put one of those red and white snow depth poles in it, and aim a camera at it, you could average a bunch of frames throughout the day into one, then maybe something like opencv to count the exposed segments?
(DIR) Post #AZLQt0CnNqqTCfSPLM by castironflower@hachyderm.io
2023-09-02T03:53:38Z
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@mjg59 "laser tape measurer" probably a smart one or usb 1 you attach to a computer
(DIR) Post #AZLTWLW6HYZcV9NJui by dymaxion@infosec.exchange
2023-09-02T04:24:17Z
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@mjg59Pretty sure marked stick, camera, and computer vision will be the easiest option if daytime-only is ok.
(DIR) Post #AZLUsFpSD4zZBaREIa by mjg59@nondeterministic.computer
2023-09-02T04:39:41Z
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Unfortunately I do not get to install any form of reference point in the river
(DIR) Post #AZLVAcZCPTlOv0apay by xabean@infosec.exchange
2023-09-02T04:42:40Z
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@mjg59 why not measure width of the surface of the water with a camera? Assuming the river banks aren't perfectly vertical that should give you a ballpark estimate minus changes due to erosion
(DIR) Post #AZLVnX5AjaVVCe6QIi by SnoopJ@hachyderm.io
2023-09-02T04:49:49Z
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@mjg59 I am nearly sure it would not be a practical solution to this problem but the way you've posed it makes me wonder what is the state of lidar remote sensing for water-level problems
(DIR) Post #AZLWfNOOydGomuluhk by jannem@fosstodon.org
2023-09-02T04:59:51Z
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@mjg59 A laser ruler should be able to in principle. Probably depends on the angle though; you want it to bounce back, not just reflect. And I don't know you can get enough precision at a reasonable cost.
(DIR) Post #AZLXAezJbjuwKtxGwS by jannem@fosstodon.org
2023-09-02T05:05:33Z
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@mjg59 Another idea is to measure the height of the waters edge to a reference point higher up. If you're using s fixed camera position it doesn't actually have to be right above it or anything. You may need to calibrate it for a few different points if the bank is not vertical. But you can interpolate between those known points well enough.
(DIR) Post #AZLXZvFmGnZk1RhX16 by sjuvonen@mastodon.online
2023-09-02T05:07:49Z
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@mjg59 Nobody seems to have mentioned https://en.wikipedia.org/wiki/Laser_rangefinder (I know nothing of them).
(DIR) Post #AZLbMLB1UTcYBVFxQm by Paxxi@hachyderm.io
2023-09-02T05:51:52Z
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@mjg59 a laser distance measure maybe? They're pretty short range though around 30-50m afaik
(DIR) Post #AZLbYBNTkViLGgjGka by robryk@qoto.org
2023-09-02T05:54:06Z
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@mjg59 if you can mount something above the water, ultrasonic distance meter will work (and this is actually a pretty common setup in reality)
(DIR) Post #AZLd00e1Lews2gIcCm by jarkman@chaos.social
2023-09-02T06:10:39Z
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@mjg59 How far away is it, and what's the angle to the horizontal, and what's the height range ? I'd try a lidar first, but I have no idea if you'd get enough signal return off the water surface.
(DIR) Post #AZLedKkGeEbFdDXJ6O by andyprice@mastodon.social
2023-09-02T06:28:40Z
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@mjg59 First you'll need a rubber duck, a yoghurt pot and some sticky-back plastic...
(DIR) Post #AZLenV7QvxSuhVDhg0 by mikee@social.lol
2023-09-02T06:29:45Z
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@mjg59 point a camera at the opposite bank, and let some software analyse the distance between the water level and the bank’s top edge.
(DIR) Post #AZLhiYhMUuu4DVMObA by tienelle@mendeddrum.org
2023-09-02T07:03:24Z
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@mjg59 My instinct is to use sonar, because running water's a horrible surface to get EM off. You'll probably need a fairly big reflector/phased array, and the HC-SR04 beloved of hobbyists runs at 40 kHz which is low enough frequency that dogs can hear it. Also it is feeble.How far away is the river, how wide is it usually, and what's your elevation above it?Another option, if you can't install reference points, is to go out and measure some rocks and trees and use them as references.
(DIR) Post #AZLjF9NHluizBe4g4W by n8@mastodon.social
2023-09-02T07:20:49Z
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@mjg59 Are you asking about real-time or on-demand?I poked at that a tad (w.r.t. the Thames and the local stairs down to the shore) ~1.55 years ago for Home Assistant, although I don't know how much note-taking I did.
(DIR) Post #AZLnZQzKOVBzQGnQ6i by dymaxion@infosec.exchange
2023-09-02T08:09:16Z
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@mjg59You can probably do it with computer vision anyway, assuming a fixed camera mounting point, you'll just need to manually provide the calibration points at different flow levels. I'd try that first.
(DIR) Post #AZLqGPnEue5u4plS7c by acesabe@mastodon.social
2023-09-02T08:39:22Z
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@mjg59Is the river tidal? Maybe there is already water level monitoring in place and the data publicly available? (If that doesn't defeat the purpose of this endeavour)
(DIR) Post #AZM4Oiey390UGWkVlI by penguin42@mastodon.org.uk
2023-09-02T11:19:12Z
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@mjg59 I wonder if a camera with and without a polariser would work?
(DIR) Post #AZMBv8ftYsJntZaa24 by sb@mas.to
2023-09-02T12:41:37Z
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@mjg59 if you can bury some pipe in the ground, you could set up something like a long water level to bring the height to a place that you can install reference marks or ultrasonic sensors.
(DIR) Post #AZMLEeu6rCzGwTcWJ6 by averagesecurityguy@infosec.exchange
2023-09-02T14:25:34Z
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@mjg59 Have you looked at https://water.weather.gov/ahps/index.php? Maybe it would solve the underlying problem of knowing the river height.
(DIR) Post #AZMYyfABWYwUTHPFAm by Stormgren@obsidianmoon.com
2023-09-02T16:59:44Z
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@mjg59 I know that CODAR is a thing for measuring wave heights and ocean currents using HF and low VHF bands, not sure how to DIY a RF based heightfinder, though. So I think the answer may be "yes" but not applicable directly to your situation, but might provide insight as to where you could find such a thing?
(DIR) Post #AZMyLilwlmApBAA1x2 by mjg59@nondeterministic.computer
2023-09-02T21:44:00Z
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@averagesecurityguy Hmm! This may actually be the easiest approach, there's a station just a few miles away. Thanks!