You can use ESP32 with GPS modules and their PPS signals. The PPS signal from the module often has has a roughly precision around 60ns against the global GPS standard.
With that signal you can PID-control an internal timer of the ESP32 - which then can be used to timestamp audio frames. Send that to a central host over Wifi and you can use your standard localization math.
The trick is to use the internal ESP32 10MHz hardware which automatically kicks timestamps into a register if a GPIO does something. Not using high-level C constructs that must eat their way through x API layers.
I've been interested in deploying something like this around my property to localize sounds that I hear just for fun.
IMO having the on-device model to pre-filter to the signals of suspected drones is potentially a good idea in a wartime environment. Not only does it conserve bandwidth (which might be a limited resource), but it also reduces airtime and thus makes the devices harder to spot.
GPS is also unreliable in Ukraine, especially near the front line.
It's unclear which approach would be better from a power budget point of view. One requires substantially more local processing power but much less radio time, while the other requires continuous radio transmission.
> GPS is also unreliable in Ukraine, especially near the front line.
There are GPS antennas that physically can block out signals that are not coming from the sky with a huge amount of decibels. Maybe Aliexpress has some of them in stock? This was heavily ITAR-ed but this ban was lifted recently.
Other option: try to sync against the DCF77 signal from Germany. Not only the beep-beep-beep time signal but also the integrated phase modulation. Jamming VLF is difficult. 77KHz is in the range of ADCs.
Then make a voter: if GPS/GLONASS/Galileo/Beidou is available prefer them, if not fall-back to DCF77. If this fails: free-running.
Cell phones are kinda nice because they're hard to ITAR. Anyone can buy them. Old and crappy ones are generally still good enough for this kind of micro model. They come with their own batteries to hold-over between power loss or overnight. They also come with their own sensors, radios, and compute already integrated. Basically, you can just write software and ignore the hardware side entirely.
Remember, this isn't planned to be a long term solution, or to provide the highest quality available, or to be the cheapest or most efficient solution. It's intended to allow Ukraine to quickly plug sensor gaps in the lines and to scale easily.
You can use ESP32 with GPS modules and their PPS signals. The PPS signal from the module often has has a roughly precision around 60ns against the global GPS standard.
With that signal you can PID-control an internal timer of the ESP32 - which then can be used to timestamp audio frames. Send that to a central host over Wifi and you can use your standard localization math.
The trick is to use the internal ESP32 10MHz hardware which automatically kicks timestamps into a register if a GPIO does something. Not using high-level C constructs that must eat their way through x API layers.
This costs like 20€.