I’m working with GPS timestamp data from a measurement, and I’m seeing a value of 316213248 seconds.
As far as I understand, GPS timestamps are typically based on the POSIX clock.
Given that the data was collected recently (in 2025), I would expect a timestamp value greater than 1.7 billion.
Does this discrepancy suggest a GPS synchronization issue or a fallback to some default/invalid time value from the GPS module?
Not sure if my answer is helpful. But, if you get the data through the brain and its service, the timestamp can be monotonic or something else. I only use monotonic, so I am not sure.
Then, you can also specify at what event you want take the time measurement using this proto message.
Thank you for your kind response.
I am using both monotonic time and GPS time data. However, I’m having trouble converting either of them into actual timestamps (i.e., year, month, day).
Is there a way to convert monotonic time into real-world time? I understand that monotonic time is based on system uptime, but I’m not sure how to determine or set the reference point to map it to a wall-clock time.
As for the GPS timestamp, it is documented to be in ‘POSIX format’, but the values seem surprisingly low. While the time intervals look consistent (so I can see how many seconds were measured), the absolute values do not match any real-world time. I’m wondering if I might be missing a base epoch or offset value when interpreting this data.
Hi, sean
Sorry for the delayed response. and it seems I misunderstood your issue.
For the conversion from monotonic to wall clock, personally I don’t really want to do it because finding out where the monotonic time starts is tricky. As far as I know, the staring point can be when the system boots up, but it can be some other events too. So, I personally won’t take this approach.
For the POSIX, although I am not familiar with it, it seems even POSIX time stamps can be either monotonic or real time according to my google search.
By the way, you might be able to get a utc stamp? Looking at this proto message(look at GPS Frame message), you can get it. Have you tried this? farm-ng-amiga/protos/farm_ng/gps/gps.proto at main · farm-ng/farm-ng-amiga · GitHub
Hi, KODAI
Yes, I was able to obtain the real-time timestamp using the utc_stamp, so that part is working now.
However, I’m still unsure why the GPS time, which is described as being in POSIX format, does not match the actual time — that remains a question for me.
That said, since I can use the UTC time, it’s not a big issue for me.
Thank you very much for your response.
I can check the POSIX time on my end as well sometime next week. It does not make you feel good when a mystery remains, haha.
