Board Choice - GPS or no GPS

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I am trying to decide which TTGO board to purchase. If my Android devices have internal GPS are there any advantages to purchasing a TTGO board with built-in GPS?

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I’ve been wondering this as well. The only reason I’ve come up with so far is that if a node is simply an unattended remote repeater (no phone connected), it would be nice to know if it started moving.

That’s an unusual concern, but I’m curious to hear others’ thoughts.

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I think that GPS is useful if you want to be independent from a phone.
For example, if you want to see the location of someone whose phone battery is dead or whose BLE connection is interrupted.

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IMO I prefer the GPS boards for the following reasons:

  • only slight price premium
  • doesn’t burn phone battery for location services (much cheaper to use the gps in the radio)
  • high res time sync (though not currently used) could eventually allow really low power consumption, because meshes could keep radios completely off (not even powering the RX side) except during a brief window at the beginning of every minute. During that window, all nodes would turn on RX and if something comes in consider the mesh ‘alive’ and then happily keep talking with each other until no more packets need to send. During the common case of no node needing to send, the nodes would instead go back asleep.
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I have both, and the T-Beams with GPS are my preferred. Even without an immediate phone BLE connection, they are up and ready to go with positions already determined and available to other nodes. When the phone is connected, everything is already there. It’s still available after disconnecting, making a stand alone unit, if needed. The non-GPS LORA32’s are acceptable, but seem lacking.

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Would this require PPS connection or can you get close enough over serial?

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I think over serial would be close enough (within a couple of seconds) but PPS would be even better (though I don’t think the TBEAMs hook up PPS)

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also one more benefit about high-res time sync:

  • All nodes could frequency hop every minute (potentially using a pseudorandom sequence based on the channel). This might help with duty-cycle limits in EU (I haven’t checked in detail).

Without a global clock frequency hopping is still possible but a global clock makes it much easier. And yes, a global clock can be generated without GPS but with GPS is is trivial and works nicely even for nodes that haven’t previously joined that particular mesh.

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