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The speaker in the video Richard Lansdowne - LoRa Geolocation mentions straight-off that he won't be quoting an accuracy for geolocation using LoRa, and it's of course not the ideal signal you would use.

A comment below the video says:

Excellent Richard, you nailed it! You've succinctly described the IoT asset tracking problem and what we need to do going forward to make this real.

So far I can't figure out, at least from the video, how this might actually be done using standard LoRa and perhaps LoRa-WAN. How would LoRa protocol estimate distance in order to triangulate, assuming that's how this works? What would be an approximate best-case accuracy based on hardware limitations? (of course your milage may vary)

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    In the same way as any other radio based reverse triangulation works, presumably. – Sean Houlihane Nov 13 '18 at 12:26
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    @SeanHoulihane I don't understand why you would say that. There are many, very different ways that a radio system can estimate distance. You could say they are all the same only until you look into the details. Considering how low bandwidth and spartan the LoRa architecture is, getting an accurate estimate of distance is particularly challenging. – uhoh Nov 13 '18 at 13:20
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LoRaWAN localization uses TDOA: Time Difference Of Arrival.

Gateways with the precise timing extension are all synchronized via GPS. When a device sends a frame, the very accurate time at which the frame was emitted is unknown, but by recording the exact time each of several gateways receive that frame (compared to GPS time), and knowing the position of gateways, you can calculate the position of the device.

On the gateway side, that requires hardware capabilities beyond what a SX130x offers, a clear view of the sky, some calibration and a clever solver somewhere is a server room.

On the device side, that requires nothing.

  • Thanks for your answer! Any idea what they are using to time off of? Is it just the synch word or something more complicated? I'm still trying to figure out LORA's secrets but progress is slow. – uhoh Jul 29 '19 at 16:21
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    Not sure if the only use the sync part (unmodulated chirps) or some other part of the frame. What I know for sure is that it requires quite a lot of additional logic that is put in a companion FPGA, so you need a SX1301 and an FPGA to get a full "ranging" gateway. – Sylvain Aug 2 '19 at 10:58
  • Wow I didn't know that, okay I'll go off and do some further reading; for some reason I am just curious how that's implemented. Thanks again! – uhoh Aug 2 '19 at 11:02

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