Show HN: Offline SOS signaling+recovery app for disasters/wars

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-...

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.

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?

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.

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 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. :|

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…)

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/

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 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.

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

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!

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.

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

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.

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

+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.

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!

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.

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.

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.

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.

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

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.

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.

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

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.

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

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!

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!!