tttt - United Nations Office for Outer Space Affairs · ICG-5, WG D Meeting, Turin, Italy,...
Transcript of tttt - United Nations Office for Outer Space Affairs · ICG-5, WG D Meeting, Turin, Italy,...
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1ICG-5, WG D Meeting, Turin, Italy, Wednesday Oct. 20, 2010
ITRF2008
Zuheir AltamimiIGN, France
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2ICG-5, WG D Meeting, Turin, Italy, Wednesday Oct. 20, 2010
Technique contributions• IVS: (1980.0 – 2009.0) : Full EOP set (91 sites)• IGS: (1997.0 – 2009.5) : PM, PMrate, LOD (492 sites)• ILRS: (1983.0 – 2009.0) : PM, LOD (89 sites)• IDS: (1993.0 – 2009.0) : PM, LOD (67 sites)
• New local ties since ITRF2005:– Tahiti : GPS SLR DORIS– Tsukuba: GPS VLBI– Herstmonceux: GPS SLR– Medicina & Noto : GPS VLBI– Greenbelt: VLBI SLR GPS DORIS– Maui/Haleakala– San Fernando : GPS SLR
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3ICG-5, WG D Meeting, Turin, Italy, Wednesday Oct. 20, 2010
ITRF2008 Network
579 sites (920 stations)
461 Sites North
118 Sites South
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4ICG-5, WG D Meeting, Turin, Italy, Wednesday Oct. 20, 2010
ITRF2008 Datum Specification
• Origin: SLR• Scale : Mean of SLR &VLBI • Orientation: Aligned to ITRF2005
using 179 stations located at 131 sites: 104 at northern hemisphere and 27 at southern hemisphere
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5ICG-5, WG D Meeting, Turin, Italy, Wednesday Oct. 20, 2010
ITRF2008: GPS/IGS Site distribution
390
102
550 discontinuities
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6ICG-5, WG D Meeting, Turin, Italy, Wednesday Oct. 20, 2010
IG1 internal precision (1997.0 - 2009.5)
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7ICG-5, WG D Meeting, Turin, Italy, Wednesday Oct. 20, 2010
SLR-ILRSA Origin wrt ITRF2008
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8ICG-5, WG D Meeting, Turin, Italy, Wednesday Oct. 20, 2010
ITRF2008 Scale: mean of VLBI and SLR
± 1ppb (6.4 mm at the equator)
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9ICG-5, WG D Meeting, Turin, Italy, Wednesday Oct. 20, 2010
Scale FORMAL errors (1 σ) via ties to GPS
Scaleppb
Scale rateppb/yr
VLBI ± 0.10 ± 0.01
SLR ± 0.12 ± 0.01
DORIS ± 0.20 ± 0.03
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10ICG-5, WG D Meeting, Turin, Italy, Wednesday Oct. 20, 2010
ITRF2008 PM residuals
X-pole Y-poleGPS 10 10DORIS 239 353
X-pole Y-poleVLBI 142 120SLR 144 128
WRMS in µas
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11ICG-5, WG D Meeting, Turin, Italy, Wednesday Oct. 20, 2010
Transformation Param Fm ITRF2008 To ITRF2005
Txmm
Tymm
Tzmm
Scaleppb
-0.5± 0.2
-0.9± 0.2
-4.7± 0.2
0.94± 0.03
Tx ratemm/yr
Ty ratemm/yr
Tz ratemm/yr
Scale rateppb/yr
0.3± 0.2
0.0± 0.2
0.0± 0.2
0.00± 0.03
At epoch2005.0
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12ICG-5, WG D Meeting, Turin, Italy, Wednesday Oct. 20, 2010
ITRF2008 Horizontal Velocity Field
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13ICG-5, WG D Meeting, Turin, Italy, Wednesday Oct. 20, 2010
ITRF2008 Vertical Velocity Field
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14ICG-5, WG D Meeting, Turin, Italy, Wednesday Oct. 20, 2010
Accuracy of ITRF2008 Origin
• Defined by SLR only• Agreement with ITRF2005
– 4.7 mm in Z-translation at epoch 2005– 0.3 mm/yr drift in X-translation
• ==> “Accuracy”: 1 cm over the time-span of SLR observations
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15ICG-5, WG D Meeting, Turin, Italy, Wednesday Oct. 20, 2010
Accuracy of ITRF2008 Scale
• Defined by the average of VLBI and SLR• Difference btw the two technique solutions:
– 1.05 ppb at epoch 2005.0– 0.049 ppb/yr
• ==> “Accuracy”: 1.2 ppb (8 mm) over the common time-span of VLBI and SLR observations
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16ICG-5, WG D Meeting, Turin, Italy, Wednesday Oct. 20, 2010
ITRF2008 precision gain
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17ICG-5, WG D Meeting, Turin, Italy, Wednesday Oct. 20, 2010
Uncertainties of the Transfer of SLR origin and SLR&VLBI mean scale to GPS frame
TXmm
TYmm
TZmm
Scalemm
0.6 0.5 0.6 0.6
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18ICG-5, WG D Meeting, Turin, Italy, Wednesday Oct. 20, 2010
WGS84 - NGA Stations in ITRF2008NGA: National Geospatial-Intelligence Agency
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19ICG-5, WG D Meeting, Turin, Italy, Wednesday Oct. 20, 2010
Conclusions
• ITRF2008 is an improved solution, compared to ITRF2005
• Accuracy of ITRF2008 origin&scale: ~ 1 cm• Future Improvement: Technique-specific
systematic errors to be mitigated– GPS uncalibrated radome– VLBI antenna gravitational deformations– SLR range/timing biases– DORIS beacon reference point behavior ?