[FOSS-GPS] Problem with RTKLIB kinematic, large residual, slip detected, ambiguity validation failed
Dean Ashby
dean at ashby.org.nz
Wed Sep 16 17:37:59 PDT 2015
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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