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“EGNOS Workshop – application”
Cracow, 24th September 2004
MAIN ASTRONOMICAL OBSERVATORY
NATIONAL ACADEMY OF SCIENCES OF UKRAINE
GPS/EGNOS Pre-Processing
experimental software "OCTAVA_PPA":
concept, possibilities, initial test results
Dr. Alexey A. Zhalilo,
Natalya V. Sadanova
1
CONTENTS
пЃ®
пЃ®
пЃ®
пЃ®
пЃ®
Possibilities and Features of "OCTAVA_PPA" software
Observation equations
Software block-diagram
General distinctions from conventional analogues
Examples of the results of processing the GPS observations
В·
IGS stations, GPS observations (RINEX v. 2.10)
В·
пЃ®
пЃ®
пЃ®
пЃ®
пЃ®
NovAtel OEM4-G2W ref. receiver (JSC "NIIRI", Kharkov),
GPS/EGNOS observations (RINEX v. 2.10)
Software Applications
Users
Prospects of the software development
Acknowledgements
Contacts
2
Possibilities and Features of
"OCTAVA_PPA" software
The “Pre-Processing” software is being created within
the framework of the Program of regional geodynamic
and ecological monitoring of the Crimea as part of
WAD/VRS algorithmic and software complex
Scientific Supervisor – Prof. Yaroslav S. Yatskiv,
Academician of the National Academy of Sciences of
Ukraine
3
Possibilities and Features of
"OCTAVA_PPA" software
(1/5)
1. The basis of the Pre-Processing&Analyses (experimental)
software "OCTAVA_PPA“ is the processing of not only the
traditional double differences (or single differences "stationstation")
of
carrier-phase
observations
but
mainly
"undifferenced" data of one separate (single) station.
2. Input data - RINEX-files of dual-frequency (and singlefrequency) GPS/EGNOS unsmoothing raw data. PPA carry out
data processing at data rates 1/30 Hz and 1 Hz. PPA software
admits the processing of RINEX-files, in which Doppler
observations are absent.
4
Possibilities and Features of
"OCTAVA_PPA" software
(2/5)
3. In the course of processing the following operations are
executed:
detection of carrier phase slips at L1 and L2 GPS/EGNOS
observations, continuity recovery (where it is possible);
detection, estimation and correction of L1 and L2 (or L1
only) phase slips both for static and kinematic modes of
measuring on the basis of processing the geometry-free linear
combinations (LC) of code and phase data for each radiolink
"satellite – GPS-station" separately as well as direct phaseonly "satellite-satellite" single differences (the principle (key)
approach);
5
Possibilities and Features of
"OCTAVA_PPA" software
(3/5)
estimation and mitigation of L1 & L2 code multipath
effects;
QC-analyses of the code and carrier phase LC and
estimation of RMS observations (C/A, P2, L1, L2) at both
frequencies (multipath, noises);
elimination (or flagged ) of abnormal observations;
recovery of continuity of code and phase observations
(elimination of local time scale jumps typical for some type of
the equipment);
calculation of ephemeredes;
6
Possibilities and Features of
"OCTAVA_PPA" software
(4/5)
synchronization (interpolation to GPS integer seconds) of
observations;
calculation of satellite clock (frequency–time) corrections (using
broadcast GPS satellite messages) and correction of observations;
correct filtering of code observations by using carrier-phase ones
(“levelling”) - for the purpose of further formation of WADcorrections, estimation of current parameters of local ionospheric
model, etc. – optionally;
data editing and formation of RINEX.OBS-file "cleared" from
carrier-phase slips and pseudorange multipath;
graphic and text displaying and registration of the results of
processing
7
Possibilities and Features of
"OCTAVA_PPA" software
(5/5)
4. The software gives the opportunity of processing the data
obtained both in the static and kinematic modes including the
objects with high dynamics.
The full version of the PPA software complex will also allow to
carry out the analogous processing of such frequently used LC,
as single-differenced "station-station" observations and
double-differenced observations.
8
Observation equations (1/2)
“Geometry-free” linear combinations (LC) of observations:
9
Observation equations (2/2)
Carrier-phase single differences
“ith satellite – jth satellite”
часы
 Lˆ 1  {  F   L ij
ij
ij
ij
ij
ij
ij
} пЂ­ пЃ„ I пЂ« C L1 пЂ­ пЃ„ N 1 ( t k ) пѓ— пЃ¬ 1 пЂ« пЃ¤ пЃ„ L 1
ij
ij
ij
ij
ij
часы
2
ij
Л†
пЃ„ L 2 пЂЅ { пЃ„ F пЂ« пЃ¤ L ij } пЂ­ пЃ§ пѓ— пЃ„ I пЂ« C L2 пЂ­ пЃ„ N 2 ( t l ) пѓ— пЃ¬ 2 пЂ« пЃ¤ пЃ„ L 2
and Wide
ij
 Lˆ wl  (
пЃ¬w
пЃ¬1
- Lane
ij
)   Lˆ 1  (
LC :
пЃ¬w
пЃ¬2
ij
)   Lˆ 2
10
“OCTAVA_PPA” software
block diagram
(1/9)
Mode of post-processing of (daily)
sessions of dual frequency observations
of separate stations
Trimble 4000SSI, NovAtel OEM4-G2W
Registration rates – 1/30 Hz, 1 Hz
11
1
3
4
2
5
DB
6
7
8
9
DB
10
11
12
”Cleared”
RINEX
END of processing
(i-th station)
12
“OCTAVA_PPA” software
block diagram
(3/9)
RINEX 2.10
(OBS- and NAV- files)
A priori information
1
2
Reading of RINEX.NAV file.
Formation of intermediate data for calculation of
frequency and time corrections and ephemeredes
3
13
“OCTAVA_PPA” software
block diagram
(4/9)
Reading of RINEX.OBS file and
transformation into internal MatLab TNP
working structure
4
Reading the header of RINEX.OBS file.
Calculation of the Antenna Phase Center data
tying to the geodetic marker
5
14
“OCTAVA_PPA” software
block diagram
(5/9)
Calculations for each epoch: О”trec , ephemeredes,
frequency and time corrections and other data for
synchronization (interpolation to GPS integer
seconds) and consequent processing
6
пЃ®
пЃ®
Editing of TNP data:
By elevation angle β≥βmin = (5о ÷ 15о)
By the results of preliminary data analysis
7
15
“OCTAVA_PPA” software
block diagram
(6/9)
Formation of “geometry-free”(GF) code and
carrier-phase linear combinations (LC) of dual
frequency observations
 “Satellite-by-satellite” processing:
detection, estimation, identification and elimination
of carrier-phase “big” slips of L1 and L2
пЃ®
8
16
“OCTAVA_PPA” software
block diagram
(7/9)
Formation and Processing
(detection, estimation, identification) of single differences
(between satellites)
of L1 and L2 carrier-phase observations.
Processing of undifferenced (one-way) carrier-phase
observations (in case of external atomic clock use)
The elimination of “small” slips –
the final correcting of slips
9
17
“OCTAVA_PPA” software
block diagram
(8/9)
пЃ®
Estimation of code observation multipath using
the filtering of “slipless” code and carrier-phase
linear combinations
Multipath compensation (correction)
Estimation of observations (C/A, P2, L1, L2) RMS
пЃ®
Marking of abnormal observations (outliers)
пЃ®
пЃ®
10
18
“OCTAVA_PPA” software
block diagram
(9/9)
Formation of RINEX.OBS-file ”cleared”
from slips and pseudorange multipath
11
Interpolation of the observations to integer GPS seconds
and elaboration of frequency-time corrections,
ephemeredes (using SV navigation message) and
navigation solution
12
Termination
of processing of the session.
Passing to session processing
of another station
19
General distinctions from
conventional analogues
(1/2)
For the determination and elimination of carrier-phase slips
the software performs the processing of “undifferenced”
observations of a separate (single) station or receiver – the
standard approach usually uses double differences
Two-stage approach of detection and elimination of “big” and
“small” slips at the expense of using the LC of observations
with “low”dynamics (Stage 1) and direct (with high
dynamics) observations of carrier-phase single differences
between satellites is used (Stage 2)
20
General distinctions from
conventional analogues (2/2)
The software uses new original algorithms of detection
and estimation of carrier-phase slips in conditions of
high dynamics and observation lapses
The principle of correlation filtering of code and
carrier-phase linear combinations for detection and
estimation of carrier-phase slips is used
21
Examples of the results of processing the GPS
observations of IGS stations
Detection, estimation, identification of “big”
carrier-phase cycle slips
(1/5)
22
Examples of the results of processing the GPS
observations of IGS stations
Detection, estimation, identification of “big”
carrier-phase cycle slips
(2/5)
23
Examples of the results of processing the GPS
observations of IGS stations
Detection, estimation, identification of “big”
carrier-phase cycle slips
(3/5)
24
Examples of the results of processing the GPS observations
of IGS stations
(4/5)
Detection, estimation, identification of “big”
carrier-phase cycle slips
25
Examples of the results of processing the GPS
observations of IGS stations
Detection, estimation, identification of “big”
carrier-phase cycle slips
(5/5)
26
Examples of the results of processing the GPS
observations of IGS stations
(1/3)
Detection, estimation, identification of “small”carrierphase cycle slips (at the example of “Wide-Lane” LC processing )
27
Examples of the results of processing the GPS
observations of IGS stations
(2/3)
Detection, estimation, identification of “small”carrierphase cycle slips (at the example of “Wide-Lane” LC processing)
28
Examples of the results of processing the GPS
observations of IGS stations
(3/3)
Detection, estimation, identification of “small”carrierphase cycle slips (at the example of “Wide-Lane” LC processing)
29
Examples of the results of processing the GPS
observations of IGS stations
(1/7)
Multipath estimation
30
Examples of the results of processing the GPS
observations of IGS stations
(2/7)
Multipath estimation
31
Examples of the results of processing the GPS
observations of IGS stations
(3/7)
Multipath Effect (Correlator Output)
32
Examples of the results of processing the GPS
observations of IGS stations
(4/7)
Multipath Effect is eliminated (Correlator Output)
33
Examples of the results of processing the GPS
observations of IGS stations
(5/7)
Multipath Effect + Cycle Slip
34
Examples of the results of processing the GPS
observations of IGS stations
(6/7)
Multipath Effect + Cycle Slip (Correlator Output)
35
Examples of the results of processing the GPS
observations of IGS stations
(7/7)
Correlator Output:detection of Cycle Slip (Multipath Effect is
eliminated )
36
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (1/21)
ZONES OF RADIOVISIBILITY OF GPS SATELLITES
Гистограмма видимости
35
30
25
20
15
10
5
0
2.4
2.6
2.8
3
3.2
3.4
время
3.6
3.8
4
4.2
4.4
4
x 10
Fig. 1
Session of observations в„–1060 dt. 15 April 2004;
the processing interval included 17700 epochs at rate 1 Hz;
beginning of the session – 10 minutes and 22 seconds past 7 a.m.
37
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (2/21)
Processing results for SV9 observations
РЈРіРѕР» Beta Sv9
Qp-Qc(b), РЎ.Р¤.Qp-Qc(r)
90
15
80
10
70
60
5
50
40
0
30
20
-5
10
0
3.9
3.95
4
4.05
4.1
4.15
4.2
4.25
4.3
4.35
4
x 10
Fig. SV9.1 - Elevation angle function
-10
3.8
3.9
4
4.1
время
4.2
4.3
4.4
4
x 10
Fig. SV9.2 - Difference of code pseudoranges
(P2-C/A) and its smoothing function
38
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (3/21)
Processing results for SV9 observations
(L1-L2) - M.o.
(L1 - L2) - m.o. Sv9
10
1.2
1
5
0.8
0.6
0
0.4
0.2
-5
0
-0.2
-10
-0.4
-15
3.8
3.9
4
4.1
время
Fig. SV9.4A
4.2
4.3
4.4
-0.6
3.8
3.9
4
4.1
4
4.2
4.3
4.4
4
x 10
x 10
Fig. SV9.4B
39
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (4/21)
Processing results for SV9 observations
дифф.(L1-L2) - дифф.сгл. функц. (с коррекцией краев)
diff. (L1 - L2) Sv9
15
0.06
0.04
10
0.02
5
0
0
-0.02
-5
-10
3.8
-0.04
3.9
4
4.1
время
Fig. SV9.5A
4.2
4.3
4.4
-0.06
3.8
3.9
4
4.1
4
4.2
4.3
4.4
4
x 10
x 10
Fig. SV9.5B
40
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (5/21)
Processing results for SV9 observations
F - M.Рѕ.
(Fw) - m.o. Sv9
60
4
50
3
2
40
1
30
0
20
-1
10
-2
0
-3
-10
-4
-20
-30
3.8
-5
3.9
4
4.1
время
Fig. SV9.6A
4.2
4.3
4.4
-6
3.8
3.9
4
4.1
4
4.2
4.3
4.4
4
x 10
x 10
Fig. SV9.6B
41
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (6/21)
Processing results for SV9 observations
(Qc-L1)-k1*(L1-L2) Sv9
15
10
5
0
-5
-10
-15
3.9
3.95
4
4.05
4.1
4.15
4.2
4.25
4.3
4.35
4
x 10
Fig. SV9.9. LC (C/A-L1) with the excluded dynamics of the ionospheric delay
42
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (7/21)
Processing results for SV9 observations
(Qp-L2)-k2*(L1-L2)
Sv9
15
10
5
0
-5
-10
-15
3.9
3.95
4
4.05
4.1
4.15
4.2
4.25
4.3
4.35
4
x 10
Fig. SV9.10. LC (P2-L2) with the excluded dynamics of the ionospheric delay
43
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (8/21)
Processing results for SV9 observations
MPQc (b), MPQp (r)
Sv9
15
10
5
0
-5
-10
-15
3.9
3.95
4
4.05
4.1
4.15
4.2
4.25
4.3
4.35
4
x 10
Fig. SV9.11. Code multipath effect (C/A (blue) and P2 (red))
44
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (9/21)
Processing results for SV26 observations
РЈРіРѕР» Beta Sv26
Qp-Qc(b), РЎ.Р¤.Qp-Qc(r)
90
15
80
10
70
60
5
50
0
40
30
-5
20
-10
10
0
2.7
2.8
2.9
3
3.1
3.2
3.3
3.4
3.5
3.6
3.7
4
x 10
Fig. SV26.1. Elevation angle function
-15
2.6
2.8
3
3.2
время
3.4
3.6
Fig. SV26.2. Difference of code pseudoranges
(P2-C/A) and its smoothing function
3.8
4
x 10
45
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (10/21)
Processing results for SV26 observations
(L1-L2) - M.o.
(L1 - L2) - m.o. Sv26
20
2.5
15
2
10
1.5
5
1
0
0.5
-5
0
-10
-0.5
-15
2.6
2.8
3
3.2
время
Fig. SV26.4A
3.4
3.6
3.8
-1
2.6
2.8
3
3.2
4
3.4
3.6
3.8
4
x 10
x 10
Fig. SV26.4B
46
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (11/21)
Processing results for SV26 observations
дифф.(L1-L2) - дифф.сгл. функц. (с коррекцией краев)
diff. (L1 - L2) Sv26
20
0.08
15
0.06
10
0.04
5
0.02
0
0
-5
-0.02
-10
-0.04
-15
-0.06
-20
2.6
2.8
3
3.2
время
Fig. SV26.5A
3.4
3.6
3.8
-0.08
2.6
2.8
3
3.2
3.4
3.6
3.8
4
4
x 10
x 10
Fig. SV26.5B
47
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (12/21)
Processing results for SV26 observations
F - M.Рѕ.
(Fw) - m.o. Sv26
60
6
40
4
20
2
0
0
-20
-2
-40
-4
-60
-6
-80
2.6
2.8
3
3.2
время
Fig. SV26.6A
3.4
3.6
3.8
-8
2.6
2.8
3
3.2
3.4
3.6
3.8
4
4
x 10
x 10
Fig. SV26.6B
48
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (13/21)
Processing results for SV26 observations
(Qc-L1)-k1*(L1-L2) Sv26
15
10
5
0
-5
-10
-15
2.7
2.8
2.9
3
3.1
3.2
3.3
3.4
3.5
3.6
3.7
4
x 10
Fig. SV26.9. LC (C/A-L1) with the excluded dynamics of the ionospheric delay
49
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (14/21)
Processing results for SV26 observations
(Qp-L2)-k2*(L1-L2)
Sv26
15
10
5
0
-5
-10
-15
2.7
2.8
2.9
3
3.1
3.2
3.3
3.4
3.5
3.6
3.7
4
x 10
Fig. SV26.10. LC (P2-L2) with the excluded dynamics of the ionospheric delay
50
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (15/21)
Processing results for SV26 observations
MPQc (b), MPQp (r)
Sv26
15
10
5
0
-5
-10
-15
2.7
2.8
2.9
3
3.1
3.2
3.3
3.4
3.5
3.6
3.7
4
x 10
Fig. SV26.11. Code multipath effect (C/A (blue) and P2 (red))
51
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (16/21)
Processing results for SBAS observations
7
3.97
Qc
x 10
Доплер [м\с]
47
3.96
46
3.95
45
3.94
44
3.93
43
3.92
42
3.91
3.9
41
3.89
40
3.88
2.4
2.6
2.8
3
3.2
3.4
3.6
3.8
4
4.2
4.4
39
2.4
2.6
2.8
3
3.2
3.4
3.6
3.8
4
4.2
4.4
4
4
x 10
Fig. SBAS.1
x 10
Fig. SBAS.2
52
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (17/21)
Processing results for SBAS observations
7
1.9
L1Sb-L1
x 10
Fn
1400
1200
1.85
1000
1.8
800
1.75
600
1.7
400
1.65
200
0
1.6
-200
1.55
-400
1.5
2.4
2.6
2.8
3
3.2
3.4
3.6
3.8
4
4.2
4.4
-600
2.4
2.6
2.8
3
3.2
3.4
3.6
3.8
4
4.2
4.4
4
4
x 10
Fig. SBAS.3
x 10
Fig. SBAS.4
53
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (18/21)
Processing results for SBAS observations
diff. Fn
diff. Fn
10
0.15
8
6
0.1
4
0.05
2
0
0
-2
-0.05
-4
-0.1
-6
-0.15
-8
-0.2
-10
2.6
2.8
3
3.2
3.4
3.6
3.8
4
4.2
2.6
2.8
3
3.2
3.4
3.6
4
4
4.2
4
x 10
Fig. SBAS.5
3.8
x 10
Fig. SBAS.6
54
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (19/21)
Processing results for SBAS observations
Fn после починки
diff. Fn после починки
0.8
0.08
0.6
0.06
0.04
0.4
0.02
0.2
0
0
-0.02
-0.2
-0.04
-0.4
-0.06
-0.6
-0.8
2.4
-0.08
2.6
2.8
3
3.2
3.4
3.6
3.8
4
4.2
4.4
-0.1
2.4
2.6
2.8
3
3.2
3.4
4
3.8
4
4.2
4.4
4
x 10
Fig. SBAS.7
3.6
x 10
Fig. SBAS.8
55
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (20/21)
Processing results for SBAS observations
(C1-L1)-mo
15
10
5
0
-5
-10
-15
2.4
2.6
2.8
3
3.2
3.4
3.6
3.8
4
4.2
4.4
4
x 10
Fig. SBAS.9
56
Examples of the results of processing the GPS/EGNOS
observations of NovAtel OEM4-G2W receiver (21/21)
Processing results for SBAS observations
(C1-L1)-mo
РЎ.Р¤. (C1-L1)
C/A noise
15
15
10
10
5
5
0
0
-5
-5
-10
-10
-15
2.4
2.6
2.8
3
3.2
3.4
3.6
3.8
4
4.2
4.4
-15
2.4
2.6
2.8
3
3.2
3.4
3.6
3.8
4
4.2
4.4
4
4
x 10
Fig. SBAS.10
x 10
Fig. SBAS.11
57
Software Applications
(1/2)
Improvement of the reliability and quality of
precise GPS-positioning in such areas as
geodesy, geodynamics, etc.
Detail analysis of observations (of reference
permanent stations) and recreating the
”cleared” from slips and code multipath
RINEX-files
As an initial tool for all possible GPS
applications
58
Software Applications
(2/2)
As software for teaching specialists and
students of Universities
As an instrument for the delicate post-fly
analysis in the automatic and interactive modes
of the results of mobile object trajectory
determinations, including aircrafts (Flight
Inspection Systems) and low orbit space
vehicles with on-board GPS equipment
59
Potential Users
Developers of algorithms and software of
processing GPS/GNSS observations
(navigation, geodesy, cadastre, GIS,
geodynamics, etc.)
Specialists of various applied centers of
processing GPS/GNSS observations
Sub-faculties of Universities specializing in the
areas: radionavigation, satellite geodesy, GIS,
etc.
60
Prospects of the Software
Development
(1/2)
Overall testing and improvement of the software
with the help of high-performance standard
software, such as BERNESE
Pre-Processing and analysis of single frequency
receiver observations
Adaptation to different sampling rates of
observations (10 Hz, 1 Hz, 1/5 Hz, 1/15 Hz)
Software adaptation to observations of SBAS
EGNOS(WAAS) , GLONASS, GALILEO
61
Prospects of the Software
Development
(2/2)
For reference permanent stations – the software
updating with the purpose of reducing the
multipath effects in carrier-phase observations
Development of the software version for
functioning in real time mode
Optional supplements – filtering the code
observations by using the carrier-phase ones – for
the tasks of formation of “noiseless” differential
RTCM and WAD corrections and estimation of
regional ionospheric models
62
Acknowledgements
The authors would like to thank the
Academician of the NAS of Ukraine,
Prof. Yaroslav S. Yatskiv, Director of the
MAO NASU for the encouragement and
overall support of the execution of the
development. Also acknowledged are the
nearest colleagues.
63
Contacts:
Main Astronomical Observatory
of the National Academy of Sciences of
Ukraine
27 Ak. Zabolotnogo St., 03680 Kiev
Tel: 380(44)-266-47-59; Fax: 380(44)-266-21-47
Email: gpsgroup@ic.kharkov. ua
64
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