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> It can also be improved; I know BLE is not _that_ effective under rubble.

It's a tough problem to solve because you're up against the laws of physics and the very boring (and often counterintuitive) "Antenna Theory". Bluetooth is in the UHF band, and UHF isn't good for penetrating anything let a lone concrete rubble.

To penetrate rubble effectively you really want to be in the ELF-VLF bands, (That's what submarines/mining bots/underground seismic sensors use to get signals out).

Obviously that's ridiculous. Everything from ELF to even HF is impossible to use in a "under the rubble" situation because of physics[1]. Bluetooth (UHF) might be "better than nothing" but you're losing at least 25-30 dBs (which is like 99.99% signal) in 12 inches of concrete rubble. VHF (like a handheld radio) can buy you another 5 inches.

Honestly I think sound waves travel further in such medium than RF waves.

[1]: Your "standard reference dipole" antenna needs to be 1/2 or 1/4 your wave length to resonate. At ELF-VLF range you need an antenna that's 10k-1k feet long. You can play with inductors and loops to electrically lengthen your antenna without physically lengthening it, but you're not gonna get that below 500-200 feet. The length of a submarine is an important design consideration when deciding on what type of radio signal it needs to be able to receive/transmit vs how deep it needs to be for stealth.

Thanks for the amazing breakdown.

That means LoRa and cellular network won't help either... That's good to know.

Yeah, sound seems like a good option. There's two points I'm struggling with though: 1. Disasters often are accompanied with a lot of noise which I'm afraid would drown or interfere with the other sound waves. 2. Mobile devices might not be able to detect the sound waves that are broadcasted.

I'll need to do more homework about those.

We'll have more flexibility with recovery for sure, so maybe that can address the shortcomings of the sound signaling...?

It still has to be cheap-ish though. Because first responders already have MUCH better tools [1].

Again, thank you so much for this comment. If you have any other suggestions or feedback, please don't hesitate to open an issue on github. Your input is awesome.

[1]: https://www.dhs.gov/archive/detecting-heartbeats-rubble-dhs-...

> That means LoRa and cellular network won't help either... That's good to know.

It does. If anyone is buried under the rubble "why don't they just tweet/SMS/mesh-network they are stuck" might be the first question someone would have. A simple answer is that the nearest GSM tower is also under rubble. But that's not enough. Even if the nearest GSM tower is 100% fine (or their next LoRa mesh peer is also fine), you need to be less than 12-15 inches of concrete (in the most optimal/reflective way) to have any signal at all. At the end of the day you're up against physics. 3 questions physics mandates:

1. What is the wavelength you're transmitting?

2. How far is your receiver?

3. What is your medium?

The keyword "Antenna Theory" or "Antenna Design" is a good rabbit hole for this sort of thing. There is this funny saying among radio enthusiasts "everything is an antenna if you squint hard enough"[1].

There is also something that cooks call "The Human Element"[2] when they're trying to evaluate the appeal of some foods to people. The "Human Element" in an "under the rubble" situation is that you want something that a normal human being would have on them when the sudden situation of an earthquake happens and they find themselves under a rubble.

I don't know what that is. I live in a place that is pretty far removed from earthquakes as a major problem. Geologically speaking, we get a "major earthquake" every 500 years or so. However, that's an average and it's been 600 years for us but the max has been 3,000 years and the min has been 200 and the mean means nothing to the individual. However, a device of some sort that can emit low frequency, low bandwidth[3], long range message seems like a useful thing. I don't know if that would be the type of device every human would have "on their body" all the time. But maybe??

[1] Everything that's electrically conductive is an RF antenna. If you get buried in the right place next to a 100 feet long rebar, you could (theoretically) send a signal that anyone in 100 mile range could hear provided you had the right equipment of course.

[2] In cooking, it is this elusive thing that explains how some cultures/people love certain tastes or textures that other cultures don't. Slimy foods in Middle Eastern or Japanese/Asian cultures vs Western Pallet for example.

[3] A device that needs to send "S.O.S" needs maybe 1byte/second or even less. You can't communicate any meaningful information in a seismic-pulse-signal type device, but "SOS" is certainly doable.

If someone is under rubble and needs to signal anyone, if they have the use of their hands, best thing they can do is get something solid and tap the SOS morse code on something. I thought that's what they did during the Kursk submarine accident but apparently that wasn't correct.

Anyway, SOS morse code will carry pretty well through concrete or steel or whatever.

TIL about Antenna Theory/Design.

Yeah the human element is the strictest here. From the little research/thinking I did, BLE felt like the most "commonly available" tool we have. But I'm wondering if manufacturing a cheap wearable could also be an option.

I definitely need to do a longer/deeper dive for this project. I overlooked it in the past, thinking people don't need it. But it seems like I just dropped the ball in distribution previously.

Using an AirTag on my dog's collar and WifiMan on my phone to track BLE signals, I could pick it up (just... not enough to interact with it, but enough to detect it above -100dbM) about 8 - 10m with a clear line of sight, and about 2m when she was in dense scrub.

So yeah, I imagine concrete is going to be even worse than a shrubbery, that said, might get some interesting propagation paths if there's metal surfaces in the rubble to reflect waves.

You could make the phones communicate via sound, not sure how it would impact the battery nor its communication range. Lots of details would have to be worked out. You have to find the frequency that communicates the longest. Perhaps do short pulses of sound to save battery life.

Unfortunately bass travels the furthest. I can hear cows a lot further away than frogs, and I can hear transport helicopters for miles (miles!)

The problem with bass sounds is ostensibly they're nondirectional. So the ideal sound for a phone would probably be the loudest pink noise they can make without blowing the speaker out.

My ham license let's me transmit on 2200 meter and 630 meter bands. I'm not allowed to use a 1100 meter or 315 meter dipole, either.

And I can only eirp 1000mW. I mean, legally. I can't eirp anywhere near that can you imagine the losses?

I think you can use 5W eirp on 630 meter, at least that's consistent with my band plan :)

It looks that for 600m you could use a vertical wire with a lot of radials :) Maybe with a balloon?

But 2200 would be fun indeed.

huh, 5W eirp. Either that changed or my memories did. cool. I also don't remember the 500W PEP ceiling, either. I thought you could drive it however hard you wanted to as long as your radiator didn't exceed [what i thought was 1000] 5000mW eirp.

Always remember that all these regulatory/legal limits don’t apply in any emergency or life preservation situations. The FCC, by law and their own rules, can’t/won’t come after you if you emit on any band with any power saying anything if you happen to be “under rubble”.

What about muon imaging?

What about Rydberg sensors for VLF earth penetrating imaging, at least?

From "3D scene reconstruction in adverse weather conditions via Gaussian splatting" https://news.ycombinator.com/item?id=42900053 :

> Is it possible to see microwave ovens on the ground with a Rydberg antenna array for in-cockpit drone Remote ID signal location?

With a frequency range from below 1 KHz to multiple THz fwiu, Rydberg antennae can receive VLF but IDK about ELF.

IIRC there's actually also a way to transmit with or like Rydberg antennae now; probably with VLF if that's best for the application and there's not already enough backscatter to e.g. infer occlusion with? https://www.google.com/search?q=transmit+with+Rydberg+antenn....

This is pretty cool! I need to learn more about both.

I imagine such fancier tools would be less available among common folks, and more among first responders.

NASA already has the tech to detect heartbeats under rubble using radar [1]. No additional equipment is needed by the rescued. The problem is emergency response can get overwhelmed in large disasters.

If Rydberg sensors would be more common, and new tech is added to mobile devices, this can seriously shift the playing field.

I will look into this, because we need out of the box solutions. Thank you!

[1]: https://www.dhs.gov/archive/detecting-heartbeats-rubble-dhs-...

"The Dark Knight" (Batman, 2009) is the one with the phone-based - is it wifi backscatter imaging - and the societal concerns.

FWIU there are contractor-grade imaging capabilities and there are military-grade see through walls and earth capabilities that law enforcement also have but there challenges with due process.

At the right time of day, with the right ambient temperature, it's possible to see the studs in the walls with consumer IR but only at a distance.

Also, FWIU it's possible to find plastic in the ground - i.e. banned mines - with thermal imaging at certain times of day.

Could there be a transceiver on a post in the truck at the road, with other flying drones to measure backscatter and/or transceiver emissions?

Hopefully NASA or another solvent company builds a product out of their FINDER research (from JPL).

How many of such heartbeat detection devices were ever manufactured? Did they ever add a better directional mic; like one that can read heartbeats from hundreds of meters awat? Is it mountable on a motorized tripod?

It sounds like there is a signal separation challenge that applied onboard AI could help with.

This is great. That said, I think that unless Apple and Google install something like this by default, it won’t get much traction, because you can’t download the app when you really need it, and most people won’t think to download it before then.

I just went through Helene in Asheville last year and it was painfully obvious that our cloud overlords have overlooked the offline disaster use case. Basically, when you’re in a situation where you desperately need technology to help, you’re on your own. I was imagining that tools like this would be great, but without the cloud, I was helpless.

Maybe instead of trying to get users to install this, it could be a proof of concept to show what’s possible, and to say to Apple and Google: install this basic lifesaving tool on every phone by default?

This is something I needed to hear for months. Thank you.

I'll work towards that. I'll need to figure out how to prove the poc is useful.

Apple's "Connect to a Satellite" touches on that, but it's not available for most of the world or on old devices. :|

Starlink is rolling out direct-to-unmodified-cellphone soon, to provide SMS connectivity to devices in locations that would otherwise be completely offline. It will work on standard, unmodified phones (if they are outside and can see the sky).

Admittedly doesn’t work under rubble, but should work in the usual/general case.

Starlink unfortunately is also not reliable for long-term just outside the US (or even inside).

How about pivoting to just infrastructureless short messaging (minus the disaster element). Would this get more people on board? (Disclaimer: I have tried and failed…)

My friend works at one of the world's largest steel plants and recently he was discussing some ideas with me about solving the problem of people disappearing during inspections and being found dead after a few days. Apparently it is a huge problem there that he wanted to build a startup around the tech.

I am saying this because I think your target market may not be people stuck under rubble, but large scale industries, construction site workers, miners, firefighters, who can install the app beforehand. Cheers.

Thanks a lot for the insight! You definitely highlighted an aspect where this tool could be monetized to fund the development of an open source project like Igatha.

Sadly today, money and connections are needed for r&d and distribution. And having a market that buys a tool like this in certain circumstances can seriously contribute to finding/building publicly available solutions.

I’ve recently had to do a deep dive into construction tech + frontline (deskless) worker tech and there is a lot of potential in this space. Very underserved market. Lmk if you’d like to chat and I can provide some insight on what we’re seeing here in terms off greenfield opportunity

I would definitely like to chat about it. Right now, it's the main picture in mind towards getting some funding to push this project forward. So, I'd love to learn more about it.

Are there any products that can act as a locator beacon, in perhaps a pager form factor? They listen for a signal from a powerful base station at frequencies low enough to deeply penetrate RF opaque material, and upon command, could key up and transmit at max power while using Time of Flight to triangulate (from a network of base stations)? 900mhz comes to mind, but perhaps there are alternate, more optimal frequency bands for this.

It's a local version of https://www.findmespot.com/

I can imagine a firefighter, miner or steelworks worker relying on the smartphone in emergency. Like, seriously, a miner, half of a mile under the rock.... Carrying smartphone?

Heavy duty wearable tags and a dense network of wall-mounted relays pinging them and triangulating 24/7 can be the only solution. Sure you can use BLE beacons for that, and this is being solved with multiple competing products as we speak (look up "locating objects in warehouse"), but specifically for the human safety applications, they would have to be imposed by the regulators. Workforce is seen as disposable and nothing short of laws and regulations is going to force employers to improve safety.

Ex miner here (grasberg, Indonesia) - yes, we all had smartphones, at all times, and yes, we rarely had signal but if you went up to the surface / anywhere with signal, you would want your phone, so we all carried them.

The majority of the worlds miners work above ground - they still run the risk of stope (wall) collapse, but they're unlikely to find themselves under half a mile of rock.

  In Australia, open-cut mining dominates coal production, accounting for over 80% of the total, while underground mining's share has decreased to around 15%. Open-cut mining is generally more efficient and cost-effective, allowing for higher recovery rates and larger-scale operations. 

  It has been estimated that more than two-thirds of the world’s yearly mineral production is extracted by surface mining. There are several types of surface mining, but the three most common are open-pit mining, strip mining, and quarrying. These differ from one another in the mine geometries created, the techniques used, and the minerals produced.

Like anybody else in the modern world, it's hard to pry smart phones away from mine workers ...

Miners warned to limit smartphones in the pit (2013) - https://www.itnews.com.au/news/miners-warned-to-limit-smartp...

This is cool! I have been really enjoying using Meshtastic and LoRa lately. It feels like a blessed relief from the toxic swamp of the regular internet. I love pinging stupid radio messages across the bay without depending on any third-party infrastructure. Maybe in addition to the literal rubble of a life threatening disaster we can use tools like this to dig ourselves out from the psychological rubble of the information superfund site we have built for ourselves

You got anyone pinging you back? I can't convince any of my friends to care.

I'm this way with trying to convince random people on the internet to chat over fldigi on HF frequencies. Hellschriber is awesome.

TIL!

---

Fldigi is a free and open-source program which allows an ordinary computer's sound card to be used as a simple two-way data modem. The software is mostly used by amateur radio operators who connect the microphone and headphone connections of an amateur radio SSB or FM transceiver to the computer's headphone and microphone connections, respectively. This interconnection creates a "sound card defined radio" whose available bandwidth is limited by the sound card's sample rate and the external radio's bandwidth. Such communications are normally done on the shortwave amateur radio bands in modes such as PSK31, MFSK, RTTY, Olivia, and CW. Increasingly, the software is also being used for data on VHF and UHF frequencies using faster modes such as 8-PSK. Using this software, it is possible for amateur radio operators to communicate worldwide while using only a few watts of RF power.

https://en.wikipedia.org/wiki/Fldigi

these days every radio has a USB port, and when plugged into a computer, shows up as a full duplex sound card plus a serial port in devices. The serial port can be used simply, or you can use the CAT interface over serial, which lets you change frequencies, modes, adjust output power, and so on. Some radios have additional interfaces for "remote waterfalls" or additional IQ "audio" for SDR software to handle the decoding, where your radio becomes just a dumb pipe and does no filtering at all.

It's all real slick, but apparently WSJT-X software (made by an academic, not meant as a slur) is slicker, and nearly everyone uses that now. It isn't designed for "rag-chewing", it's designed for propagation testing and "contesting"; it's real dull after you've made dozens of contacts really far away.

Lately when i actually transmit with fldigi, i will use a web SDR like kiwi to "listen" to myself. Since the radio has a soundcard, and my PC has a soundcard, i can route websdr to one "modem" and my radio to another, and decode my own transmissions.

that's also boring!

Another interesting protocol that supports LoRa is Reticulum, which uses an announce based system for bandwidth efficiency instead of Meshtastic's flood based routing.

TIL thanks for sharing those!

What's not clear to me is, who's listening? Like if I install this app and I get buried under a crumbled building and send out the SOS signal... Are there any receivers???

People, nearby, with the app installed who open it during a disaster. That's why it needs to be in more hands.

Ideally, there would be an option to have your phone "listen" in the background and notify you if anyone needs help. I haven't added that yet.

For now: let's say I'm in a neighborhood. An earthquake happens, a building collapses. I have the app installed and I'm fine. So, I open it and I get close to each building and check if there are any survivors under it.

You'll keep broadcasting, until your battery runs out. It's not heavy on the battery, so it can broadcast for a while.

I'll clarify that in the readme.

Great idea... But appears to be not practical.

I agree it's not practical in its current state.

The more important problem right now is signaling. Recovery is a much more flexible problem to solve.

there was some work on using apple's underlying BLE / mesh network they use for their tracking devices, but with open / alt devices

Something like that could be useful if anyone with an iphone going nearby the signal was enough to pick it up, without them requiring to have the app installed.

This is exactly the goal. It was a little difficult to do, so I just postponed it.

TLDR; Apple devices scanning in the background require a lot of workarounds [1].

Another comment suggested proposing this to Apple [2]. If this were built by Apple internally, it would be game-changing. A little delusion never hurt anyone :seenoevil:

[1]: http://www.davidgyoungtech.com/2020/05/07/hacking-the-overfl...

[2]: https://news.ycombinator.com/item?id=43552544

Check out the tech behind avalanche beacons for some inspiration. They are meant to locate bodies buried deep in snow debris fields within a meter precision. You have to also have a beacon to search for another beacon.

Surprising as it may seem, avalanches are easier to avoid [1] and easier to handle it comes to communication[2]. To an extent of course[3].

[1] I used to be terrified of the concept of an Avalanche. However, at the end of the day you're only exposed to an Avalanche if you choose to be or live next to a large mountain in the winter. It's not even like Hawaiians living next to an active volcano. All you have to do (in terms of living) is to move away during Avalanche season. Hawaiians atleast have the excuse of "it hasn't erupted in 10 years"-maybe. THe other example is if you're a skiing/winter-sport enthusiast (like me). And you simply balance your chance of an avalanche vs the reports and "how much fun it sounds to ski with your friends"

[2] If you find yourself in an avalanche situation, you need/must do your best to "swim" to the top of the avalanche. There is gear that can help you do so outside of beacons or "signal based" notifications. Once you've established all those unfeasible, you're left with the same tools a "sudden earthquake victim" is up against. You still have the upper hand because a simple handheld transceiver (from like Icom, Kenwood or Yaesu) will have 100x the range through snow vs one through liquid water or concrete.

[3] Physically speaking: ice is eventually going to behave like water under enough depth. I think.

[4] Avalanche Gear example: https://alpenglowsports.com/collections/avalanche-safety

Satellite based emergency services are already enabled in recent Android phones.

I know that only because recently I have been getting a notification on my Pixel 9 Pro that Satellite based emergency services are going in and out of coverage for some reason. I never even knew it existed until my phone told me it was down lol.

At this moment they only cover some countries, but it might be well worth focusing on building out this tech instead of trying to make something new.

It's awesome that it's coming to Android as well. I was mind blown when I got it on my phone traveling between Spain and Portugal by car.

It's hard to find a one-size-fits-all solution. I don't know if satellite coverage would still be available under rubble. It's definitely valuable in other situations.

The country coverage is a huge part. My country will likely not get satellite coverage in the next 5 to 10 years. Such countries is where disaster response is worse and infrastructure is more prone to failure.

BLE might be useful above ground in some situations, e.g., a person who is unable to stand and is located in a large field of tall grass, or someone who is hiding from an attacker and wants to silently request help.

For the specific case of burial under rubble it might be better to work on sensing sounds rather than using radio broadcasts. If the person can move they may be able to tap on concrete with another piece of concrete. Using three or more phones (plus BLE or WiFi for timing coordination) placed on the rubble it might be possible to triangulate the location of the tapping. While there are professional (expensive) versions of this (like the heartbeat detector mentioned above), giving the capability to everyone could be useful. Adding the BLE emission/detection couldn't hurt and when the trapped person runs the app it could give them instructions to maximize their chances of detection. For tapping those instructions might be to tap three times once every five minutes to minimize the physical energy required. That would mean the three sensing phones would need to wait 5 to 10 to 15 minutes to do detection and acquire a location. Tapping on stones could work by itself since people can put their ears to the rubble and listen for the tapping, so the main benefit of the app might be just to tell the person what they should do in their situation (tell the trapped person to tap 3 times every five minutes, tell the rescuer to listen for 3 taps occurring every five minutes, providing a timer to indicate the 5 minute intervals could be useful too). Five minutes might not be optimal, some research would be needed on that, and it may depend on the energy level of the trapped person so perhaps the sensing cell phones should be left in place for hours or days. Ideally all phones would have this as an emergency app that would provide advice and help with BLE beacons, timers, cellular calls, sensing, and whatever in any situation.

In general this seems like a difficult problem and worthy of some extended research.

+1 to sound, I'm planning to research that thanks to all the helpful HN comments like yours :D

I find the "instruction app" a little limited because a person needs to be conscious, they need to be calm and collected to remember to open the app, and their phone needs to be accessible.

In its current state, providing instructions is better than just broadcasting BLE which will be weakened and lost by rubble.

In my country, a lot of first responders still rely on asking people to scream if they can hear them. Anyone unconscious would be discovered days later...

There has to be some way of providing an automated signal of life.

The comments about the physics limitations are pretty awesome. They make me wonder if we can assist it in any way... I learned about passive resonators recently. I know they have a short distance transmission, but maybe if they were part of the building material?

I need to start by learning more about the physics. I know I'm limited by it, but maybe there's window we can walk through instead of the door.

Cool idea and this was nostalgic as well... I created a similar application to communicate and send beacon signals over SMS (using Twilio) without Internet (as internet went down) during emergency SoS situation motivated by 2015 Chennai floods...

Suggestion: You can possibly try if you can use OpenHaystack [1] to send some "unknown tracker found nearby" alert to any nearby iPhone even if the receiver device doesn't have your app installed or use the FindMy network to send arbitrary data for your app's communication. [2]

[1] https://github.com/seemoo-lab/openhaystack

[2] https://github.com/positive-security/send-my

As a thought, not tested, using wifi probe requests might be better through more dense material scenarios. Using a specific AP probe request "SOS Request" from the device would help discover over all the other AP requests that others are throwing. No idea if iOS or Android would let you hijack that process.

This is a bit more extreme, but some type of triangulation from multiple rescuers could be useful in closing in on a spot.

This is really interesting and thanks for sharing.

I collected a list of alternative options for signals that I'll be looking into [1]. I included wifi probe requests as well. Thank you so much!

[1]: https://github.com/nizarmah/igatha/issues/5

Have you considered making the app to take a GPS reading then turn off the GPS to save battery life? If the person say is trapped in rubble they likely not going to move afterwards thus you can relay this location information to nearby receivers.

This is really smart. I did not!

In my situation, GPS was being jammed. That made GPS not useful at all. I tried my best to avoid it for that and battery usage.

But this initial reading and turning it off is just genius. I added to the list. Thank you so much!

This is awesome. Technology put to good use.

Can voice be transferred? Message be recorded and rebroadcasted?

What about making the device vibrate SOS pulses. The person at stake might not have the strength to tap or bang, may be able put the phone on a metallic surface and send vibrations?

I appreciate it :D

Those two questions are spot on.

Voice cannot be transferred yet. Re-broadcasting might require a bluetooth meshnet.

Vibrations are a great idea. They are not that battery intensive. They also can be detected by 3rd party tech.

Both were added to the list of ideas. Thank you!!

I haven't done any effort there, because I want to get this into hands.

Have you considered alternating signals using different radio frequencies? And then use differences in signal arrival times for more accurate location? Also I guess using different bands might be more universal, as signal loss would be different depending on environment and band used.

I have not, yet. Right now, it's more of a "signaling life" tool.

Improvements are definitely needed with location, but the signal loss as you mentioned is higher priority and restricts what can be used for location.

I'm planning to do my homework about alternatives to help mitigate the signal loss. And from there, the options for location might be clearer.

The EU is mandating Apple to implement WiFi-Direct https://www.ditto.com/blog/cross-platform-p2p-wi-fi-how-the-...

WiFi doesn't fare any better than BLE under rubble unfortunately, but WiFi is going to be a useful technology to build disaster response tools in general

That's awesome. We really need something stable and cross platform.

I'm not a fan of how Apple managed to make background BLE advertising and scanning work only with its own devices.

There is one thing that could make this insanely valuable. The bad news is that this thing is outside your control: No phone that I know of ships with a LoRa chip. Though to be fair, the only reason why LoRa (and by extension LoRaWAN and Meshtastic) are reliable and robust is precisely because they are not common at all.

This is great. Is there a version of this that does p2p off-grid messaging? Use cases from: 1. Coordination between group members during camping in the wilderness. A mesh solution that works across iOS and Android would be ideal but mesh isn't a hard requirement either. 2. Messaging within a group who's flying together but across different seats/sections at cruising altitude in a long haul flight.

Not right now. There are applications out there that do p2p off-grid messaging.

Some of them might require you open the application the first time ever while on internet.

There are many out there (on the App/Play store) that support both use cases you mentioned, I just can't list any off the top of my head because it's been a while since I used one.

Do smart phones support "LE Long Range (Coded PHY, S=8)" Perplexity says it can transmit up to a 1km in ideal conditions. Otherwise it's 10-30m indoor.

Receiving signals doesn't. Advertising likely does. So if someone has proper equipment, they probably can identify the signals.

Ideal conditions is likely open spaces with no interference. Walls and concrete lower that as you mentioned.

I'm hoping it can help if people are standing right next to the rubble, whether BLE or the "siren" sound.

I have no guarantees though. I haven't properly tested because I haven't thought of a low cost option yet.

I'm asking if smart phones support LE Long Range

Hey neuroelectron! I'm sorry. I misunderstood your question, initially.

I don't know if phones support LE Long Range. I will look into it [1]. Thank you!!

[1]: https://github.com/nizarmah/igatha/issues/5

Silica gel was at the core of a cool water collection contraption to collect moisture in the dessert . Now add this and the ability to sinter sand together in the dessert and you could print windstills with robots.

Okay, what is "disaster detection"? I'd really prefer my phone not chirp noise over Bluetooth channels if I don't notice and respond to a notification in time.

Would be nice if the readme included the current method to detect disaster and the nature of the "SOS" signal. Is that something Bluetooth has a behaved protocol for, or is it really just chirping?

1. Disaster detection is a user toggle-able option that uses motion sensors to detect extreme shifts. 2. SOS signal is a BLE broadcast along with an alarm-like audio (generated from a sine wave).

+1, I usually have it off, but toggle it on when I'm in a bad setting. It can be made more accurate with time, especially with onboard ML models.

It is a Bluetooth protocol (BLE Scanning and Advertising, if you'd like to learn more about it).

I'll be sure to update the readme. Thank you for the great questions!!

It would be interesting to see if some of the earthquake advanced warning notifications could be integrated too. at least then it would be an "official" warning. seems like false positives would be possible with the device's motion sensors even with an "i'm okay" type of cancel.

I LOVE this. Thank you! Huge +1, even though it's not going to be easy.

Yeah, false positives are the largest problem. The barometer sensor helps reduce them, but it's not available on all phones.

Machine learning can help a lot here, but I haven't looked for publicly available data yet.

Excellent! Good to know it uses the standard BLE advertisement for the SOS and doesn't need WiFi or GPS.

Well thought out. Excellent work. Thank you for making this available as open source!

Side note -- I wonder if it's possible to have a companion system to scan regularly for the signal at home for the elderly. Then notify caregivers from the companion using available wifi/cell if the SOS is detected. Since it's so well behaved it seems like even having a regular wellness check mode would be possible. Having a companion system for relay would allow the app itself to never need WiFi/cell and have independent care notifications protocols that wouldn't need to be maintained in the app.

Thanks a lot for the kind words!

That's a really cool idea. Kudos!! A companion system should be relatively easy. It's also two single devices communicating with each other which makes things much simpler to build as well. This is worth looking closer into.

It would be nice to have a button to play a loud sound. A common use case is to play it when you are under ruin and you hear rescuers close to you. If the rescuers heard a loud sound, they can locate you quicker.

I don't know the amount of battery that is necessary to do that.

The current "Send SOS" plays a loud sound from the speaker, with the SOS beacon.

To cut time, I didn't modify the volume programmatically. So the user would need to have their volume set at 100%.

This needs improvement, especially considering my phone is always muted.

Likewise, the battery usage needs better testing.

How many people in my city or neighborhood must install the app (and use it, watch notifications) for it to serve its purpose?

It of course depends on the disaster, but in case of war this app can be used to find survivors for purposes other than saving them.

Great idea though.

Every person being rescued must have the app. Only one person rescuing needs to have the app.

It'll be easy to find a collapsed building site. The person rescuing just needs to be close to the site with the app. Otherwise, the signal might not be noticed.

+1 regarding finding survivors for malicious purposes. I tried my best to lower the surface area of that happening. It's still possible in edge cases, like opposing soldiers finding the people transmitting SOS, but they need to be extremely close to do that.

Might be rough on battery life, but perhaps pulsing an SOS with the flashlight?

It is rough, but I like it if it's "toggled" when needed.

If the person doesn't respond to an "Are you conscious?" alert, maybe allow responders to "toggle" certain actions like the flashlight you mentioned.

A meshnet for communicating back-and-forth between devices. Permissions might be tricky though.

I feel like this has some potential overlap with the PulsePoint app (that one is for CPR/AED emergencies rather than large scale disasters), so that could be a potential partnership to look into.

Thanks! I didn't know about it. They seem pretty mature, but I will reach out to them.

There's LoRa runs on 450/900 MHz with complete stack for transmitting and relaying messages. There's even modern encrypted protocol (meshstatic) built on it.

Another comment mentioned that as well. TIL. I'll look into this before anything else [2].

Cross-platform bluetooth between Android/iOS is too annoying sadly. If LoRa can help address those issues, it would simplify things a lot.

[1]: https://news.ycombinator.com/item?id=43552585

[2]: https://github.com/nizarmah/igatha/issues/5

this is good but ideally people want this app/platform to be embedded in hardware/OS level

Not really high tech but worth mentioning that some shortwave portable radios (a world radio receiver is an item you should have in your earthquake emergency supplies) have a portable blare out alarm horn function to signal your presence to first responders.

Although it has the obvious limitation that you would have to be within arm's reach of it before you were to be trapped in a collapsing building, and sound can travel sufficiently under rumble.

From "Homemade AI drone software finds people when search and rescue teams can't" https://news.ycombinator.com/item?id=41764486#41775397 :

> {Code-and-Response, Call-for-Code}/DroneAid: https://github.com/Code-and-Response/DroneAid

> "DroneAid: A Symbol Language and ML model for indicating needs to drones, planes" (2010) https://github.com/Code-and-Response/DroneAid

> All but one of the DroneAid Symbol Language Symbols are drawn within upward pointing triangles.

> Is there a simpler set of QR codes for the ground that could be made with sticks or rocks or things the wind won't bend?

Kudos for all your hard work! Getting to 1.0, getting on the app store, and making something that should be on all phones - you did awesome!

I would change your license so it can’t be stolen by Apple. At the very least they need to buy it or hire you as employee.

There's a higher chance a person/company can do something valuable with this than Apple buying it or hiring me as an employee.

I will also try to create a monetized version for specific use. Maybe that can help fund building a solution that's publicly available.

Both of those will increase the chances of it being adopted by smartphones, like Google and Apple. That's why I switched from GPL-3.0 to MIT.

I appreciate the kind words and the awesome suggestion. Thank you!