[FOSS-GPS] Problem with RTKLIB kinematic, large residual, slip detected, ambiguity validation failed
Felipe G. Nievinski
fgnievinski at gmail.com
Thu Sep 17 15:36:56 PDT 2015
try to rule out real-time issues
by saving the data streams as
files on disk and post-processing
using the rtkpost GUI instead of the
rtkrcv CUI. ask it to save residuals
and inspect them graphically using
rtkplot.
-F.
On Thu, Sep 17, 2015 at 4:00 PM, <foss-gps-request at lists.osgeo.org> wrote:
> Message: 1
> Date: Thu, 17 Sep 2015 12:37:59 +1200
> From: Dean Ashby <dean at ashby.org.nz>
> To: foss-gps at lists.osgeo.org
> Subject: [FOSS-GPS] Problem with RTKLIB kinematic, large residual,
> slip detected, ambiguity validation failed
> Message-ID: <55FA0B67.3030503 at ashby.org.nz>
> Content-Type: text/plain; charset="utf-8"
>
> Hi,
>
> I'm relatively new to RTKLIB but have done quite a bit of reading over
> the past few weeks so please bear with me if I've missed something obvious.
>
> When running rtkrcv in kinematic mode talking to a base station running
> str2str via tcpcli I very rarely get a FIXED solution, usually it's just
> a FLOATING solution.
>
> I see a lot of this:
>
> rtkrcv> error
> 00:17:18.00: slip detected (sat=14 rcv=1 LLI1=3)
> 00:17:18.00: slip detected (sat=25 rcv=1 LLI1=3)
> 00:17:18.00: ambiguity validation failed (nb=6 ratio=1.44 s=25.24/36.30)
> 00:17:19.00: slip detected (sat=14 rcv=1 LLI1=3)
> 00:17:19.00: slip detected (sat=16 rcv=1 LLI1=3)
> 00:17:19.00: slip detected (sat=25 rcv=1 LLI1=3)
> 00:17:19.00: ambiguity validation failed (nb=6 ratio=1.45 s=29.42/42.56)
> 00:17:20.00: slip detected (sat=25 rcv=1 LLI1=3)
> 00:17:20.00: ambiguity validation failed (nb=6 ratio=1.46 s=31.24/45.48)
> 00:17:21.00: slip detected (sat=16 rcv=1 LLI1=3)
> 00:17:21.00: slip detected (sat=25 rcv=1 LLI1=3)
> 00:17:21.00: ambiguity validation failed (nb=6 ratio=1.45 s=34.00/49.20)
> 00:17:22.00: slip detected (sat=14 rcv=1 LLI1=3)
> 00:17:22.00: slip detected (sat=25 rcv=1 LLI1=3)
> 00:17:22.00: ambiguity validation failed (nb=6 ratio=1.31 s=37.35/49.06)
>
>
> I've seen various other posts where people have had similar problems but
> that has ofte been put down to cheap patch antennas and poor SNR.
> Admittedly I'm using cheapish active patch antennas sitting on sheets of
> spare 3mm aluminium to act as ground planes, located in reasonably clear
> space on three sides, and the satellite SNR looks OK:
>
> rtkrcv> obs
>
> TIME(GPST) SAT R P1(m) P2(m) L1(cyc) L2(cyc)
> D1(Hz) D2(Hz) S1 S2 LLI
> 00:17:55.0 G01 1 23173440.00 0.00 -67934004.25 0.00
> 4321.2 0.0 42 0 2 0
> 00:17:55.0 G03 1 20996503.04 0.00 -80470547.61 0.00
> 8531.9 0.0 43 0 2 0
> 00:17:55.0 G04 1 23901429.65 0.00 -56298544.87 0.00
> 3864.9 0.0 44 0 2 0
> 00:17:55.0 G14 1 23016147.60 0.00 -48310509.64 0.00
> 3804.7 0.0 35 0 2 0
> 00:17:55.0 G16 1 23683356.32 0.00 -27092194.48 0.00
> 10341.1 0.0 32 0 2 0
> 00:17:55.0 G22 1 25079322.86 0.00 -38665003.76 0.00
> 2944.1 0.0 28 0 3 0
> 00:17:55.0 G23 1 22642174.23 0.00 -44392777.77 0.00
> 9568.9 0.0 47 0 2 0
> 00:17:55.0 G25 1 23260380.39 0.00 -70004514.13 0.00
> 4404.1 0.0 30 0 3 0
> 00:17:55.0 G26 1 21612855.57 0.00 -63585920.57 0.00
> 9476.4 0.0 45 0 2 0
> 00:17:55.0 G31 1 19896070.95 0.00 -79557949.56 0.00
> 5677.5 0.0 44 0 2 0
> 00:17:55.0 G32 1 19775470.02 0.00 -84790957.79 0.00
> 6361.9 0.0 49 0 2 0
>
> 00:17:55.0 G01 2 23428649.54 0.00 123118157.28 0.00
> 0.0 0.0 42 0 0 0
> 00:17:55.0 G03 2 21251709.44 0.00 111677473.40 0.00
> 0.0 0.0 48 0 0 0
> 00:17:55.0 G04 2 24156636.48 0.00 126942627.26 0.00
> 0.0 0.0 41 0 0 0
> 00:17:55.0 G14 2 23271350.71 0.00 122291627.81 0.00
> 0.0 0.0 33 0 0 0
> 00:17:55.0 G16 2 23938559.50 0.00 125797319.77 0.00
> 0.0 0.0 43 0 0 0
> 00:17:55.0 G22 2 25334523.53 0.00 133133154.17 0.00
> 0.0 0.0 26 0 1 0
> 00:17:55.0 G23 2 22897381.47 0.00 120326137.93 0.00
> 0.0 0.0 49 0 0 0
> 00:17:55.0 G25 2 23515585.12 0.00 123575137.32 0.00
> 0.0 0.0 29 0 1 0
> 00:17:55.0 G26 2 21868061.88 0.00 114917375.21 0.00
> 0.0 0.0 44 0 0 0
> 00:17:55.0 G31 2 20151273.77 0.00 105894595.55 0.00
> 0.0 0.0 51 0 0 0
> 00:17:55.0 G32 2 20030674.09 0.00 105260781.87 0.00
> 0.0 0.0 47 0 0 0
>
> There are a few things here that seem unusual though. My understanding
> is that the first block of satellites are from the local (serial) GPS
> receiver and the second block are from the base station. The P and L
> values seem to significantly different, and the doppler (D) values don't
> exist for the base station. This strikes me as very odd as I have seem
> some other examples on-line where these values are much closer matches.
>
> Rtkrcv appears to be receiving RTCM messages from the base station
> according to the status output:
>
> rtkrcv> sta
>
> Parameter : Value
> rtklib version : 2.4.2
> rtk server thread : -1227946896
> rtk server state : run
> processing cycle (ms) : 100
> positioning mode : kinematic
> frequencies : L1
> accumulated time to run : 00:28:52.7
> cpu time for a cycle (ms) : 45
> missing obs data count : 0
> bytes in input buffer : 0,0
> # of input data rover :
> obs(1732),nav(24),gnav(0),ion(657),sbs(3431),pos(0),dgps(0),ssr(0),err(0)
> # of input data base :
> obs(1733),nav(25),gnav(0),ion(0),sbs(0),pos(114),dgps(0),ssr(0),err(0)
> # of input data corr :
> obs(0),nav(0),gnav(0),ion(0),sbs(0),pos(0),dgps(0),ssr(0),err(0)
> # of rtcm messages rover :
> # of rtcm messages base :
> 1002(1733),1004(1733),1005(57),1006(57),1019(670)
> # of rtcm messages corr :
> solution status : float
> time of receiver clock rover: 2015/09/17 00:25:50.000480056
> time sys offset (glo-gps)(s): 0.000000000
> solution interval (s) : 1.000
> age of differential (s) : 0.001
> ratio for ar validation : 1.160
> # of satellites rover : 11
> # of satellites base : 10
> # of valid satellites : 10
> GDOP/PDOP/HDOP/VDOP : 1.6,1.5,0.8,1.2
> # of real estimated states : 3
> # of all estimated states : 124
> pos xyz single (m) rover : -4603225.267,603993.316,-4358763.701
> pos llh single (deg,m) rover: -43.38549245,172.52487221,56.564
> vel enu (m/s) rover : 0.062,-0.092,-0.162
> pos xyz float (m) rover : -4603225.267,603993.316,-4358763.701
> pos xyz float std (m) rover : 0.233,0.137,0.204
> pos xyz fixed (m) rover : -4603228.149,604003.890,-4358765.385
> pos xyz fixed std (m) rover : 0.038,0.049,0.022
> pos xyz (m) base : -4603224.437,603994.410,-4358758.516
> ant type rover :
> ant delta rover : 0.000 0.000 0.000
> ant type base :
> ant delta base : 0.000 0.000 0.000
> pos llh (deg,m) base : -43.38546274,172.52485749,52.507
> vel enu (m/s) base : 0.000,0.000,0.000
> baseline length float (m) : 5.365
> baseline length fixed (m) : 12.282
> monitor port : 0
>
> I can supply my configs and more information about the hardware and
> software version if necessary but this message was getting large enough
> as it was and I thought the information above might be enough to
> diagnose what I am missing.
>
> Any help much appreciated.
>
> Regards,
>
> Dean
>
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