Author Topic: Setting date and time and reading logs  (Read 2066 times)

a.alexeev.p

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Setting date and time and reading logs
« on: April 15, 2021, 12:52:56 pm »
Hi,

I would like to take a PAW track and compare it accuracy against another device I have. I think I figured out how to read the logs, but got a few questions:

- There is AMSL altitude in the log, but how is it derived if local pressure on the day is never input? Or is there some smart GPS algorithm that does it?
- The date and time I see in the home page is very wrong - how can I set it and make sure it is correct to a second?

Thank you!

Admin

Re: Setting date and time and reading logs
« Reply #1 on: April 15, 2021, 04:52:34 pm »
Hi

can you provide the exact messages you are referring to, and where you think they may be incorrect ?

Thx
Lee

a.alexeev.p

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Re: Setting date and time and reading logs
« Reply #2 on: September 08, 2021, 05:07:03 pm »
Hi! I am also very curious re the altitude part of the question :-) Are you able to clarify pleasE?

exfirepro

Re: Setting date and time and reading logs
« Reply #3 on: September 09, 2021, 08:50:48 am »
Hi Alex,

I guess your initial query wasn’t answered as Lee was waiting for more detailed response from you.

Two general comments:-

1. PAW knows the local barometric pressure from the sensor on the Bridge and works out relative altitude(s) (which is what we are primarily interested in) using a complicated algorithm involving local barometric pressure, GPS altitude and comparison with local transponder and ADSB reports.

2. The initial date and time on the PAW Home Screen at startup relate to the software update, not ‘real time’ and are automatically ‘corrected’ once the unit receives time stamp data from the GPS satellites, hence there is no need for manual correction.

Hope this helps.

Best Regards

Peter

a.alexeev.p

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Re: Setting date and time and reading logs
« Reply #4 on: September 09, 2021, 08:17:11 pm »
thank you so much! so that means that in theory normal aircraft altimeters could always show correct AMSL altitude if it also had such a sensor built in without the need to input QNH? But then when airborne and travelling far away with pressure changing -how could it maintain accuracy? and basically are you saying GPS is not involved at all in PAW trying to determine the altitude?

Admin

Re: Setting date and time and reading logs
« Reply #5 on: September 11, 2021, 11:41:24 am »
FTAOD

PAW has 2 altitude references
GNSS (provided by GPS receiver)
Barometric (referenced against 1013.25mb standard pressure)

When reporting altitude to systems such as SkyDemon, we provide both altitude references, although I am pretty sure SkyDemon ignores the barometric and uses the GNSS altitude

When comparing altitude differences against a transponder, then we use the Barometric reference
When comparing against other PAW or FLARM then we use the GNSS reference

Thx
Lee

a.alexeev.p

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Re: Setting date and time and reading logs
« Reply #6 on: September 24, 2021, 12:14:59 pm »
Interesting... and what about altitude recorded in PAW logs?

I was just always sure that somehow the baro altitude and GPS allows you to get the true altitude since with PAW in SkyDemon I always tend to see altitude super accurate when compared to my altimeter, however, when I use just my tablet GPS - then the output appears to be significantly off. But what you are saying is - I am likely seeing GPS altitude and for some reason it is very accurate (eg better receiver)?

Admin

Re: Setting date and time and reading logs
« Reply #7 on: September 25, 2021, 11:40:30 am »
Interesting... and what about altitude recorded in PAW logs?
What is the question, not sure I understand ?
which logs are you referring to, do you mean track files ?
If so, then we use 2 references GNSS(GPS) and PGRMZ(BARO)
so the track file info contains records of the form
Quote
$PGRMZ,1797,F,2*02
$GPGGA,160717,5050.874,N,00102.985,W,1,08,1.2,671.4,M,46.6,M,,*51

Quote
I was just always sure that somehow the baro altitude and GPS allows you to get the true altitude since with PAW in SkyDemon I always tend to see altitude super accurate when compared to my altimeter, however, when I use just my tablet GPS - then the output appears to be significantly off. But what you are saying is - I am likely seeing GPS altitude and for some reason it is very accurate (eg better receiver)?
Can't comment on the accuracy of location services TBH, apple do not declare how they calculate this, or what chipset they use

Thx
Lee

Paul_Sengupta

Re: Setting date and time and reading logs
« Reply #8 on: September 27, 2021, 08:43:08 pm »
Most tablets and phones don't have WAAS/EGNOS capable receivers built in.