3.2.1.2015 effects of interoperability of coordinates-icg 10.ppt · 2015-11-17 · galileo...
TRANSCRIPT
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Yang Y, Qin X, Zeng A
1. China National Administration of
GNSS and Applications (CNAGA)
2. State Key lab of Geo-information
Engineering
Effects of Interoperability of GNSS Coordinate
System
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Introduction1
2
3
4
IF of diff gravitational cons on ephemeris
IF of diff rotation rate on ephemeris
Effects of diff cons on positioning
Contents
5 Conclusions
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� Background
� Multi GNSSs using
together should
provide better PNT
performance than
relying solely on
one system if the
systems compatible
and interoperable
GPS (31) GLONASS (24)
BDS (35) Galileo (27)
User
1. Introduction
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1. Introduction
� Background
� Interoperable open signals can
� improve the observed geometry
� increase reference fame stations
� increase time keeping clocks
� compensate systematic errors
� compensate random errors
The requirements are compatibility and
interoperability!
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� GPS---WGS 84
� GLONASS---PZ-90
� BDS---CGCS 2000 or BDC 2000
� Different geometrical reference ellipsoids
� Different gravitational constants
� Different rotation velocity
� Different reference frame
� Different updating period
� The status of GNSS coordinate references
1. Introduction
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Broadcast ephemeris
Ground control system
Orbit & its prediction
Fitting of orbit parameters
Reference ellipsoid constants, reference frame,
gravitational constant and earth’ rotation velocity
Tracking stations Monitoring stations
2. Effects of Grav Cons on ephemeris
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Original gravitational
constant of GPS
GM =3.986005××××10-14 GM=3.986004418××××10-14
Since 1994, the
gravitational constant
of GPS
Reduces about 1.2m
orbit radial errorExisting receivers
use the original GM
� Change of GPS gravitational constant
2. Effects of Grav Cons on ephemeris
OrbitsReceivers ?
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Gravitational cons GM
((((m3/s2))))
Rotation rate
((((rad/s))))
GPS 3.986005××××10-14 7.2921150××××10-5
GLONASS 3.986004418××××10-14 7.2921150××××10-5
Galileo 3.986004415××××10-14 7.2921151467××××10-5
BDS 3.986004418××××10-14 7.2921150××××10-5
IERS 3.986004418××××10-14 7.2921150××××10-5
� Gravitational constant and earth rotation rate
of GNSS
⊕ω
2. Effects of Grav Cons on ephemeris
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∆GM)
0
x
y
ω
z
y
x
(t2GM
1r∆ k ⋅
−
⋅+
⋅⋅=⊕
&
&
&
v
oek ttt −= (time starting from reference epoch)
[ ]Tzyxr &&&&v = (satellite velocity vector)
� Effect of ∆GM on orbit
Effects of ∆GM
changes with
Observation time tk
Satellite position
Satellite velocity
2. Effects of Grav Cons on ephemeris
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Effect of GM on Orbit of GPS03
� Effect of ∆GM on orbit
614 105.821083.98600441-3.986005∆GM ×=×= )(
� ΔΔΔΔGM=GMGM=GMGM=GMGM=GM
GPSGPSGPSGPS
----GMGMGMGM
IERSIERSIERSIERS
Effect of GM on all GPS orbits
2. Effects of Grav Cons on ephemeris
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� Different GM will result
in orbit error to 2m
� The effects of ∆GM on
the satellite orbits are
different for different
epochs
� The effects of ∆GM on
different satellite orbits
are different
� Analysis of Effect ∆GM on orbit
2. Effects of Grav Cons on ephemeris
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3. Effects of rotation velocity on orbits
⊕⋅⋅
−= ∆ωt
0
x
y
r∆ k
v
� Effects of rotational velocity on orbit⊕∆ω
� GPS starts its broadcast ephemeris according to the second
of GPS week, thus the biggest effect of the rotation rate on
the orbit appears at the last day of the GPS week
Effects of rotation
rate changes
Observation time tk
Satellite position⊕∆ω
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ωGalileo – ωIERS=
-12-5 101.467 107.292115 - 677.29211514∆ω ×=×=⊕
)0(
Effects of ∆ω on GPS03
� Effects of rotational rate on orbit⊕
∆ω
⊕∆ω
Effects of ∆ω on all GPS sats
3. Effects of rotation rate on ephemeris
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� Effect analysis of on Effect analysis of on Effect analysis of on Effect analysis of on
orbitorbitorbitorbit
⊕∆ω
� If substitute Galileo’s rotational rate into GPS orbit
determination software , then will produce error
more than 10m on the GPS orbit
� It should be noted that Galileo system uses a different
earth rotation velocity from those of other GNSS, or
from IERS recommended value
⊕∆ω
3. Effects of rotation rate on ephemeris
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Semi-major axis (m)))) FlattingFlattingFlattingFlatting
GPS 6378137.0 298.257223563
GLONASS 6378136.0 298.25784
Galileo 6378136.5 298.25769
BDS 6378137.0 298.257222101
IERS 6378137.0 298.2572221008827
� Ellipsoid geometrical constants of GNSS
(Cheng P et al 2009)
4. Effects of reference ellipsoid constants
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� The semi-major axis of
GPS (WGS 84) and BDS
(CGCS 2000) ellipsoids are
the same, only the flatting is
different
� Different GNSS uses
different flatting of ellipsoid
� Effect of ellipsoid constants on GNSS positioning
4. Effects of reference ellipsoid constants
� Difference of semi-major axis of the reference ellipsoid will
only affect the height and the latitude, not the longitude
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⋅
−
−−−
−+
−
+
+
⋅
−+
+−
+
⋅
−+
+−
+
+−+
−+−
+
−+−
+
⋅
++−
++−
+−
=
df
da
f1
B)sinBsinBsineM(1B)sine(1
a
N00
f)H)(1(M
B)sinBcosBsineM(2
H)a(M
sinBcosBNe
m
BsinNeH)(N
0HM
sinBcosBNe
ε
ε
ε
0sLsinBcosBcoNenLsinBcosBsiNe
1tgBsinLHN
H)eN(1tgBcosL
HN
H)eN(1
0cosLHM
BsinNeH)(NsinL
HM
BsinNeH)(N
z
y
x
sinBconsBsinLcosBcosL
0H)cosB(N
cosL
H)cosB(N
sinLHM
cosB
HM
sinBsinL
HM
sinBcosL
dH
dL
dB
2222
222
22
2
z
y
x
22
22
2222
0
0
0
� Effects of
∆a, ∆f,
[x0, y0, z0],
(εx,εy,εz) as
well as the
scale m on
positions
4. Effects of reference ellipsoid constants
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� Latitude effects of diff ellipsoids
4. Effects of reference ellipsoid constants
-100 -50 0 50 100
-0.00002
-0.00001
0.00000
0.00001
0.00002
Latitude(Degree)CGCS2000-0.002
-0.001
0.000
0.001
0.002GTRF -0.002
-0.001
0.000
0.001
0.002PZ90.11
-100 -50 0 50 100
-0.00002
-0.00001
0.00000
0.00001
0.00002
LatitudeCGCS2000-0.002
-0.001
0.000
0.001
0.002GTRF -0.002
-0.001
0.000
0.001
0.002PZ90.11
Effect btw GPS & BDS
-100 -50 0 50 100
-0.000010
-0.000005
0.000000
0.000005
0.000010
LatitudeCGCS2000-0.00010
-0.00005
0.00000
0.00005
0.00010GTRF-0.0004
-0.0002
0.0000
0.0002
0.0004PZ90.11
Effect btw GPS & GalEffect btw GPS & Glo
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-100 -50 0 50 100
0.00000
0.00003
0.00006
0.00009
0.00012
Latitude(Degree)
CGCS2000-0.04
-0.03
-0.02
-0.01
0.00GTRF -0.05
-0.04
-0.03
-0.02
-0.01
0.00PZ90.11
-100 -50 0 50 100
0.00000
0.00004
0.00008
0.00012
Latitude
CGCS20000.46
0.47
0.48
0.49
0.50GTRF0.960
0.975
0.990
1.005PZ90.11
-100 -50 0 50 100
-0.000010
-0.000005
0.000000
0.000005
0.000010
Latitude
CGCS20000.4980
0.4985
0.4990
0.4995
0.5000GTRF 0.996
0.997
0.998
0.999
1.000PZ90.11
Effect btw GPS & BDS Effect btw GPS & GalEffect btw GPS & Glo
�Height effects of diff ellipsoids
4. Effects of reference ellipsoid constants
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� Effects of GPS & BDS ellipsoids on both of the
latitude and Height are about 10-6s (or 0.1mm) . It
may be neglected
� However, different a btw GPS (or BDS) and Galileo
(GRTF) as well as GLONASS (PZ90) will result in
error of 0.001s (or 3cm) and 0.0015s (or 4.5cm) in
latitude respectively
� Height effects arrives at 0.5m and 1m respectively
� Effect analysis of ellipsoid constants
4. Effects of reference ellipsoid constants
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5. Effects of diff reference frames
� Effects of reference frames
� Differences of coordinate frames are usually reflected
in satellite orbits
� If CGCS2000 is selected as positioning system, the
corrections of the linearized GPS observation
equations will contain the effects of reference frames
and systematic orbit errors
� If single differencing positioning method is employed,
only the remain errors of reference frames affects the
positioning results
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Error of satellite orbit
Errors of baseline vector
rij
rj
s Ratio of Ranging btw stations and btw
satellite and stations
� Coordinate system errors will be reduced by
differentiating the observations of near stations
5. Effects of diff reference frames
� Effects of reference frames
Influence function
Frame errors orbit errors positioning errors
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5. Effects of diff reference frames
<5cm
� Effects of coordinate system offsets on single differential positioning
Influences of single differentiation positioning by the
coordinate offsets are 1m, 5m, 10m, 20m respectively
0 10 20 30 40 50 60 70 80 90 1000
0.01
0.02
0.03
0.04
0.05
基 基线线 (km)
差差差差单单
(m)
星 星星基卫 卫MEO H=20000km
1 m
5 m
10 m
20 m
0 10 20 30 40 50 60 70 80 90 1000
0.01
0.02
0.03
0.04
0.05
基 基线线 (km)
差差
差差
单单
(m)
星 星星基卫 卫GEO/IGSO H=36000km
1 m
5 m
10 m
20 m
Meo satellites with H=20000km GEO/IGSO satellites with H=36000km
Baseline length (km) Baseline length (km)
Single diff ra
nge erro
r (m)
Single diffe
range erro
r (m)
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1. As broadcast ephemeris is related to the gravitational
constant GM and the rotation velocity ωωωω of the earth,
they should be consistent to those of ephemeris
2. Original GM of GPS and present one are different,
the orbit error more than 1m will be introduced
(Receiver and broadcast ephemeris still use the
original one for consistency)
3. Different rotational velocity affects satellite orbits.
The biggest error will arrive at several ten meters
4. Broadcast ephemeris is not related to semi-axis a, thus
different a does not affect user positioning
5. Summary
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5. If GNSS positioning results need to be transformed to
geodetic ones, the parameters of different ellipsoids
should be used for different countries
6. The different frames of GNSS will result in satellite
orbit errors with several cm or dm, then systematically
affect the single point positioning results
7. The interoperability parameters should be introduced
into functional models; or using differential positioning
to reduce the effects
8. BDS coordinates connected to CGCS2000 by GPS
observations, thus additional errors are included
5. Summary
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9. Coordinates updating strategies of BDS and GPS are
different. GPS updates them to every June 30, which
reduces deformation effects
10.Multi GNSS receivers should be used for
tracking stations. The plate moving information
from the ITRF and IGS should be used for
generating the interoperability parameters
5. Summary
The idealized reference coordinate system of GNSS
should be Interchangeable!
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Thank you!