2 talkers for 1 gps mouse (sirfstar iii)?

[Patrick Weemeeuw]

For one physical receiver (a gps mouse), I get consistently 2
readings:
1. GPSD,O=GND ...
2. GPSD,O=MID2 ...

patrick@eee2:~$ gpspipe -w
GPSD,X=1250415386.577536,I=SiRF binary GSW3.2.2_3.1.00.12-SDK003P1.01a
GPSD,W=1
GPSD,O=GND ? 0.005 50.917848600 4.715925900 ? 2.020 2.370 ? ? ? ? ? ?
3
GPSD,O=MID2 1250415388.000 0.005 50.917850166 4.715921743 36.317
33.000 34.988 0.0000 0.000 0.000 ? ? ? 3
GPSD,O=GND 1250415388.000 0.005 50.917848600 4.715925900 36.317 2.020
2.370 0.0000 0.000 0.000 ? ? ? 3
GPSD,O=MID2 1250415389.000 0.005 50.917850166 4.715921743 36.317
33.000 34.988 0.0000 0.000 0.000 ? 35.02 ? 3
GPSD,O=GND 1250415389.000 0.005 50.917848600 4.715925900 36.317 2.020
2.360 0.0000 0.000 0.000 ? 35.02 ? 3
GPSD,O=MID2 1250415390.000 0.005 50.917850166 4.715921743 36.317
33.000 34.988 0.0000 0.000 0.000 ? 35.02 ? 3
GPSD,O=GND 1250415390.000 0.005 50.917848600 4.715925900 36.317 2.020
2.370 0.0000 0.000 0.000 ? 35.02 ? 3
GPSD,O=MID2 1250415391.000 0.005 50.917850166 4.715921743 36.317
33.000 34.988 0.0000 0.000 0.000 ? 35.02 ? 3
GPSD,O=GND 1250415391.000 0.005 50.917848600 4.715925900 36.317 2.030
2.360 0.0000 0.000 0.000 ? 35.02 ? 3
GPSD,Y=MID4 1250415391.990 7:9 34 265 37 1:27 54 271 29 1:28 45 60 26
1:22 6 328 18 0:18 28 304 38 1:15 81 201 29 1:8
15 73 21 1:
GPSD,O=MID2 1250415392.000 0.005 50.917850166 4.715921743 36.317
33.000 34.988 0.0000 0.000 0.000 ? ? ? 3
GPSD,O=GND 1250415392.000 0.005 50.917848600 4.715925900 36.317 2.040
2.360 0.0000 0.000 0.000 ? ? ? 3
GPSD,O=MID2 1250415393.000 0.005 50.917850166 4.715921743 36.317
33.000 34.988 0.0000 0.000 0.000 ? 35.04 ? 3
GPSD,O=GND 1250415393.000 0.005 50.917848600 4.715925900 36.317 2.060
2.360 0.0000 0.000 0.000 ? 35.04 ? 3
GPSD,O=MID2 1250415394.000 0.005 50.917850166 4.715921743 36.317
33.000 34.988 0.0000 0.000 0.000 ? 35.06 ? 3
^C

The O=GND is much more accurate (e.g. horizontal error 2 vss 33) (33
is perhaps on the high side, but this is an indoor measurement).

According to the gpsd manual, MID2 and GND are tags:
    "A tag identifying the last sentence received. For NMEA devices
this is just the NMEA sentence name; the talker-ID portion may be
useful for distinguishing among results produced by different NMEA
talkers in the same wire."

Applications get most often the MID2 one, as that is typically the
most recent one received. I would like to select the GND one, and
ignore the MID2. Is there a means to make gpsd to do that?

Further I'm wondering about the underlying cause of this.

Thanks



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[Chris Kuethe]

Much like in NMEA there are multiple, differently structured, SiRF
messages that carry position information. The receiver gratuitously
emits a number of these in binary mode; we parse them and pass their
content on. Your client app should be the one making these quality
decisions; the gpsd daemon should just pass the data along.

As for the error factors, they're both lies. One is very optimistic
(SiRF native), one is very pessimistic (gpsd-computed). The truth lies
somewhere in between. The receiver has some internal state that we
don't when we recompute the error estimates.

On Wed, Aug 26, 2009 at 1:53 PM, Patrick Weemeeuw<pweemeeuw@...> wrote:

> For one physical receiver (a gps mouse), I get consistently 2
> readings:
> 1. GPSD,O=GND ...
> 2. GPSD,O=MID2 ...
>
> patrick@eee2:~$ gpspipe -w
> GPSD,X=1250415386.577536,I=SiRF binary GSW3.2.2_3.1.00.12-SDK003P1.01a
> GPSD,W=1
> GPSD,O=GND ? 0.005 50.917848600 4.715925900 ? 2.020 2.370 ? ? ? ? ? ?
> 3
> GPSD,O=MID2 1250415388.000 0.005 50.917850166 4.715921743 36.317
> 33.000 34.988 0.0000 0.000 0.000 ? ? ? 3
> GPSD,O=GND 1250415388.000 0.005 50.917848600 4.715925900 36.317 2.020
> 2.370 0.0000 0.000 0.000 ? ? ? 3
> GPSD,O=MID2 1250415389.000 0.005 50.917850166 4.715921743 36.317
> 33.000 34.988 0.0000 0.000 0.000 ? 35.02 ? 3
> GPSD,O=GND 1250415389.000 0.005 50.917848600 4.715925900 36.317 2.020
> 2.360 0.0000 0.000 0.000 ? 35.02 ? 3
> GPSD,O=MID2 1250415390.000 0.005 50.917850166 4.715921743 36.317
> 33.000 34.988 0.0000 0.000 0.000 ? 35.02 ? 3
> GPSD,O=GND 1250415390.000 0.005 50.917848600 4.715925900 36.317 2.020
> 2.370 0.0000 0.000 0.000 ? 35.02 ? 3
> GPSD,O=MID2 1250415391.000 0.005 50.917850166 4.715921743 36.317
> 33.000 34.988 0.0000 0.000 0.000 ? 35.02 ? 3
> GPSD,O=GND 1250415391.000 0.005 50.917848600 4.715925900 36.317 2.030
> 2.360 0.0000 0.000 0.000 ? 35.02 ? 3
> GPSD,Y=MID4 1250415391.990 7:9 34 265 37 1:27 54 271 29 1:28 45 60 26
> 1:22 6 328 18 0:18 28 304 38 1:15 81 201 29 1:8
> 15 73 21 1:
> GPSD,O=MID2 1250415392.000 0.005 50.917850166 4.715921743 36.317
> 33.000 34.988 0.0000 0.000 0.000 ? ? ? 3
> GPSD,O=GND 1250415392.000 0.005 50.917848600 4.715925900 36.317 2.040
> 2.360 0.0000 0.000 0.000 ? ? ? 3
> GPSD,O=MID2 1250415393.000 0.005 50.917850166 4.715921743 36.317
> 33.000 34.988 0.0000 0.000 0.000 ? 35.04 ? 3
> GPSD,O=GND 1250415393.000 0.005 50.917848600 4.715925900 36.317 2.060
> 2.360 0.0000 0.000 0.000 ? 35.04 ? 3
> GPSD,O=MID2 1250415394.000 0.005 50.917850166 4.715921743 36.317
> 33.000 34.988 0.0000 0.000 0.000 ? 35.06 ? 3
> ^C
>
> The O=GND is much more accurate (e.g. horizontal error 2 vss 33) (33
> is perhaps on the high side, but this is an indoor measurement).
>
> According to the gpsd manual, MID2 and GND are tags:
>    "A tag identifying the last sentence received. For NMEA devices
> this is just the NMEA sentence name; the talker-ID portion may be
> useful for distinguishing among results produced by different NMEA
> talkers in the same wire."
>
> Applications get most often the MID2 one, as that is typically the
> most recent one received. I would like to select the GND one, and
> ignore the MID2. Is there a means to make gpsd to do that?
>
> Further I'm wondering about the underlying cause of this.
>
> Thanks
>
>
>
> _______________________________________________
> Gpsd-users mailing list
> Gpsd-users@...
> https://lists.berlios.de/mailman/listinfo/gpsd-users
>

--
GDB has a 'break' feature; why doesn't it have 'fix' too?
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[Eric Raymond-3]

Patrick Weemeeuw <pweemeeuw@...>:
> The O=GND is much more accurate (e.g. horizontal error 2 vss 33) (33
> is perhaps on the high side, but this is an indoor measurement).

That's interesting, and not what I'd expect.
 

> According to the gpsd manual, MID2 and GND are tags:
>     "A tag identifying the last sentence received. For NMEA devices
> this is just the NMEA sentence name; the talker-ID portion may be
> useful for distinguishing among results produced by different NMEA
> talkers in the same wire."
>
> Applications get most often the MID2 one, as that is typically the
> most recent one received. I would like to select the GND one, and
> ignore the MID2. Is there a means to make gpsd to do that?
>
> Further I'm wondering about the underlying cause of this.

They're both sentences emitted by SirF chips at different points in
their cycle, analogous to the way many NMEA devices redundantly emit
GPRMC/GPGGA/GPGLL.  We process both because in older firmware versions
the timestamp in the GND report is garbage.

Currently there's no way to suppress GND. It is possible we could do that
in the driver, but I'd need to see evidence from people with different usage
patterns before I'd take that relatively drastic step.

I have a feature request in my queue for the new protocol, to implement
filtering commands.  I will bear in mind that some people may want
to filter on tags as well as data classes.
--
                <a href="http://www.catb.org/~esr/">Eric S. Raymond</a>
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