Re: [gpsd-dev] [Patch Submission] $GPVTG w/magnetic course

[teyrana]

Okay, after a fair bit of discussion, Here's new patch for $GPVTG parsing:

## Sample Output:

```

$GPHDT,185.38,T*02

{"class":"ATT","heading":185.38}

$GPGGA,140133.00,4221.8535752,N,07101.8901618,W,2,06,0.8,12.205,M,-33.056,M,7.0,0138*48

{"class":"TPV","status":2,"mode":3,"lat":42.364226253,"lon":-71.031502697,"alt":12.205}

$GPVTG,171.90,T,186.54,M,0.05,N,0.10,K,D*22

{"class":"TPV","status":2,"mode":2,"track":171.9000,"magtrack":186.5400,"speed":0.026}

. . .

```

## Patches: 

- 1 of 2 - https://pastebin.com/uGG9jH30

- 2 of 2 - https://pastebin.com/m0i19iWV

Daniel Williams

address@hidden

858-220-8134 (Mobile)
github.com/teyrana
LinkedIn

On Thu, May 31, 2018 at 6:59 PM, Gary E. Miller <address@hidden> wrote:

Yo teyrana!

On Thu, 31 May 2018 18:46:33 -0400
teyrana <address@hidden> wrote:

> > I've not look at that code, so take care that users of
> > compass_variation can tell good from bad data in that field. 
>
> Are you referring to "users" internal to gpsd (like the struct -> json
> code)? or client applications? ...

Yes,

> > > grep -Rn -e compass_variation   *.c 
>
> gps.h:1853:    double compass_variation;

Hehehe.  I guess it then needs to be added in libgps_json.c and gpsd_json.c
before anything use can be had of it.

But since we are starting pretty much from scratch, how about just adding
a new variable in gps_data_t for magnetic track, righ next to the
current true north track.

Be sure it gets initialized to NaN.  Then modify libgps_json.c and gpsd_json.c
to use it.


> ... (plus my addition).  Does this match your experience?

Sorry, I have no experience with that variable.

> Do you have any external projects in mind, that we should check with?

None come to mind.

RGDS
GARY
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