Re: 2 separate positions pass through gpsd

[Gary E. Miller]

Yo Filip!

On Thu, 13 Oct 2022 12:11:45 +0200
Filip Kubicz <filip.kubicz@tier.app> wrote:

> First of all, thank you for adding passing the control commands to the
> receiver through gpsd. It was really a big improvement and a
> simplification to our application!

Glad to help.

> I have a question:
> From 1 receiver, I need to pass 2 separate positions
> 1. final Dead Reckoning-computed position (GNRMC, GNGNS, PQTMINS and
> others) 2. GNSS-only position (coming from a receiver debug command
> PQTMGPS)

I'm confused.  You skipped over a bunch of details.  What GNSS recevier
sends PQTMINS or PQTMGPS

I know of know GNSS receiver that reports 2 different positions...

> These 2 might differ, and the position 1. might be very very wrong in
> some cases.

Sounds like a bug in the receiver.

> Chip supplier is working on improvements (Quectel LC29D),

Oh, Quectel.  Good grief.  Before the "improve" things they should fix
all their bugs.

> however I need to gather more data and be able to tell how big are
> differences, and for the time being add logic in the application that
> discards position 1. if it's too far away from the GNSS-only.

Every other DR receiver does that for you.  Quectel should not make the
client do that.

> For the GNSS-only position, I tried to distinguish it by assigning it
> a different status - e.g. STATUS_SIM that will never be used in this
> application.
> 
> The problem with using status field is that it is cached by gpsd.

gpsd does not cache anything.

> If
> there occurs a higher status in the beginning of the reporting cycle,
> it will be also used for all TPV reports in this cycle:

Got any documentation on this mess?  I can do nothing until I have doc.

> Implementation of PQTMINS is here, if needed:

I'm not looking at code without doc.

Once you get this project doc, can you get me some working samples?

> I also tried using unused variables in the gps_fix_t struct, but this
> is also not a perfect solution, as wanglem and wangler get rounded:

We can add new variables in gps_fix_t if needed.  But if you are getting
rounding errors on doubles, you got big problems.

RGDS
GARY
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        gem@rellim.com  Tel:+1 541 382 8588

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    "If you can't measure it, you can't improve it." - Lord Kelvin

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