Re: Gpsd information showing as nan in application

[raaj lokanathan]

Hey Luke,

No it’s not ublox gnss receiver. 

On Thu, 26 Mar 2020 at 4:01 PM, Luke Hutchison <address@hidden> wrote:

Do the NaN values ever disappear, so that you get only valid values? If so, can you watch the values and see if you see either of the altitude values alternating between two values, a few meters apart, within each 1 second update window?

Is this a u-blox receiver?

You may need to try switching between binary mode and NMEA mode, maybe even switching back and forth a couple of times, either to get rid of the NaN values, and/or to duplicate the other behavior I described above, where the receiver alternates between two different altitude values (for both altitude fields) a few meters apart. You can see how I switched the receiver mode in my bug report about this, by telnetting to gpsd and then issuing ?DEVICE={"native":0} and ?DEVICE={"native":1}:

https://gitlab.com/gpsd/gpsd/issues/59

On Thu, Mar 26, 2020 at 1:50 AM raaj lokanathan <address@hidden> wrote:

Yes exactly that’s what is happening now.

On Thu, 26 Mar 2020 at 3:15 PM, Luke Hutchison <address@hidden> wrote:

Right, but are these NaN values interspersed with non-NaN values, i.e. do the reported values alternate between NaN and non-NaN? If so, this seems to be the same issue I have been seeing. I tried reporting this recently on this mailing list, and in the gpsd bug tracker.

The other variant of this issue (it is intermittent) is that the receiver alternates between two 3D positions, a few meters apart, and the alternation happens once per second, with the two different versions being reported in quick succession.

On Thu, Mar 26, 2020, 12:59 AM raaj lokanathan <address@hidden> wrote:

Hi Luke,

Yes exactly one each per second I can see the nan values.

On Thu, 26 Mar 2020 at 2:23 PM, Luke Hutchison <address@hidden> wrote:

Do the values alternate between NaN and a non-NaN value, once each per second?

On Wed, Mar 25, 2020 at 11:59 PM raaj lokanathan <address@hidden> wrote:

I just checked my nmea sentence to see whether are there any problem with my heading information which shows NAN sometimes. By looking at it I can confirm that the all the nmea sentence such as gprmc gpvtg are having the same heading values.

Then in which case it shows NAN? From where the NAN values are coming from?

On Thu, 26 Mar 2020 at 1:37 PM, raaj lokanathan <address@hidden> wrote:

Just curious, why the gpsd is not handling the NAN values itself?

Which means each time I develop a application I have to check for the NAN is it?

On Thu, 26 Mar 2020 at 1:38 AM, Gary E. Miller <address@hidden> wrote:

Yo raaj!

On Wed, 25 Mar 2020 17:24:50 +0800
raaj lokanathan <address@hidden> wrote:

> Just would like to know the NAN is it something expected from gpsd?

Yes.  Very intentional.

> Why is it getting NAN values?

NAN is the simplest way to mark a floating point value as invalid.  It
save having to create a valid flag for each and every floating point
value.

Read up on IEEE 754.

RGDS
GARY
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Thanks and regards,

Raaj Lokanathan

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Thanks and regards,

Raaj Lokanathan

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Thanks and regards,

Raaj Lokanathan

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Thanks and regards,

Raaj Lokanathan

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Thanks and regards,

Raaj Lokanathan