GPS Time Sinch Epoch


I am running some tests to determine the accuracy of the GPS receive time of a LoRa frame in the RAK 2245 sitting on top of the Raspberry Pi.

I am running two RPi’s each with a RAK 2245 with the GPS antenna. They are both running Chirpstack base 5.27.2 and sending their data to my Chirpstack server running in the cloud.

So I have two of these gateways running in the same house. The GPS has resolved the location of each gateway accurately, The way I am running this test is that I have one LoRa WAN sensor, that sends a frame every few seconds. I am then looking at the metadata of that in Chirpstack metadata.

As you can see, although I have anonymised some fields, there is a decent GPS location resolution but the timeSinceGPSEpoch is way out. It almost feels as if this field is not populated from a GPS timestamp at all, but just the regular system clock.

Does anyone have any advice or has anyone looked into this before?

Thanks for your time and interest.

It looks correct to me, see below for the conversion to UTC: