Products IGS
-
Upload
mydearest-bennett -
Category
Documents
-
view
235 -
download
0
Transcript of Products IGS
-
8/10/2019 Products IGS
1/29
Jan Kouba
Geodetic Survey Div.
NRCan
Canada
IGS Products and Applications
-
8/10/2019 Products IGS
2/29
Content
IGS Combined Products
Objectives
Description
Precision/availability
Consistency
Use of IGS Products
Relative Positioning
Precise Point Positioning/Navigation
Compatibility
Scientific Applications
IGS Products Limitations and Solutions
Future Developments
-
8/10/2019 Products IGS
3/29
IGS PRODUCTS
Support practical positioning and scientific applications of GPS, such as
surveying, navigation and national geodetic control networks
monitoring of Earth rotation, deformation and atmosphere (trop. & ion.)
easy access and contributions to ITRF, time transfers, etc.
Provides convenient and precise IGS reference system through
the core IGS combined products: orbits, Earth rotation parameters (ERP), station
positions/velocities and satellite/station clocks
additional combined products, consistent with the core products: tropospheric
zenith path delays (ZPD), ionospheric TEC (total electron count) maps and
associated rec./satellite diff. calibration biases (DCB)
IGS combined orbits (since 1994) ; clocks and ERP (since 1995); station
positions (since 1996) and tropospheric ZPD (since 1997)
IGS Products are more precise and reliable than the individual AC solutions
(up to 8 Analysis Center solutions combined)
-
8/10/2019 Products IGS
4/29
IGS Product Description
Core Combined Products: orbits/clocks/ ERP/station positions
IGS Final orbit, clock and ERP combined solutions (12 day delay)
IGS Rapid orbit, clock and ERP combined solutions (17 hour delay)
IGS Predicted orbit and clock combined solutions (1 hour before the observation day) Nine Associate ACs (AACs) produce regional station position solutions in SINEX format
Up to eight ACs, AACs contribute global orbit, ERP, global station position (SINEX)
solutions and up to five ACs clock solutions
Combined Zenith Path Delay (ZPD)
seven ACs, produced by GFZ, since Jan. 1997
Weekly files by site, 2 hour resolution (four weeks delays)
Combined Global Ionosphere Maps of Total Electron Content (TEC)
Five ACs, AACs, Combined TEC and DCBs (Differential Code Biases) in IONEX format,
produced by ESA since June 1998
Daily files, 2 hour resolution (four weeks delay)
-
8/10/2019 Products IGS
5/29
Analysis Center Functions
IGS Analysis Centers (AC): are the basis of all IGS products, improved IGSproducts are largely due to AC improvements
Typically performs continuously (daily): three types of global solutions(Predicted, Rapid and Final) utilizing complex and sophisticated software, often
developed in house over many years
Conforming to IGS/IERS standards, but innovations are encouraged.
Documentation on an each AC
) approach is at the IGS CB Archives:
http://igscb.jpl.nasa.gov/igscb/center/analysis/
ccc
.acn
Continuously involved in research & developments: striving for the bestsolutions and sharing scientific results amongst AC colleagues
Helpful and healthy competitions amongst all ACs
Associate Analysis Centers (AACs):
typically do not perform all global solutions, e.g. the Rapid only, or only certainspecific solution products, such as:
RNAAC (Regional Network AAC), GNAAC (Global Network AAC), IAAC(Ionospheric AAC) etc.
-
8/10/2019 Products IGS
6/29
IGS PRODUCT Table
IGS Combined Product Precision
Product Available Interval Precision
Satellite Orbits&clocks orbits clocks
Predicted Real-time 15 min 50 cm 30 ns
Rapid 17 hours 15 min 10 cm .5 ns
Final 12 days 15 min 5 cm .3 ns
IGS Combined (Prelim.) Station Positions Velocities
Weekly solutions 2-4 weeks 7 days 3-5 mm 1-3mm/y
Earth Rotation Parameters parameters rates/LODRapid PM 17 hours 1 day .2 mas. .4 mas/d
Final PM 12 days 1 day .1 mas .2 mas/d
Rapid UT /LOD 17 hours 1 day .10 ms .06 ms/d
Final UT /LOD 10 days 1 day .05 ms .03 ms/d
Tropospheric ZPD
-
8/10/2019 Products IGS
7/29
IGS Orbit Improvement
1994 to Mid 1999
-
8/10/2019 Products IGS
8/29
IGS PRODUCTS (AC performance)
BROADCAST (BRD), IGS PREDICTED (IGP) and IGS UTRA_RAPID
(IGU) ORBIT RMS WITH RESPECT TO THE IGS RAPID (IGR)
ORBITS
0
1
2
3
4
5
6
7
16-Nov-99 16-Dec -99 15-Jan-00 14-Feb-00 15-Mar-00 14-Apr-00 14-May-00
DATE
WEIGHTEDRMS(m)
brd
igp
igu
-
8/10/2019 Products IGS
9/29
IGS Orbit Comparison
-
8/10/2019 Products IGS
10/29
Earth Rotation Parameters
-
8/10/2019 Products IGS
11/29
Consistency of IGS Products
Consistent with the current international conventions
International Earth Rotation Service (IERS) Conventions 1996
International Terrestrial Frame (ITRF)(currently ITRF97)
IGS CORE products (orbits/clock/ERP/stations) are mutually consistent
Since December 1998, combination of minimally constrained AC solutions
Nearly exact ITRF transformations (e.g. for the ITRF97-ITRF96 and the future
changes)
ITRF realizations used for IGS Products (for more details see the presentationon: IGS ITRF Realization and Transformations) :
ITRF92 - Jan 2, 1994(Wk 0730) to Dec 31, 1994 (Wk 0781) ITRF93 - Jan 1, 1995(Wk 0782) to Jun 29, 1996 (Wk 0859)
ITRF94 - Jun 30, 1996(Wk 0860) to Feb 28, 1998 (Wk 0946)
ITRF96 - Mar 1, 1998(Wk 0947) to July 31, 1999 (Wk1020)
ITRF97 - Aug 1, 1999(Wk 1021) to present (since Feb 27, 2000 IGSITRF97 (SINEX))
IGS satellite clock solutions are aligned to the GPS time via broadcast clockcorrections:
-
8/10/2019 Products IGS
12/29
USE of IGS PRODUCTS
IGS Products greatly enhance and simplify (no need for complex global
GPS solutions) all GPS analyses and applications such as:
Positioning/navigation
Global, Regional and Local
Relative positioning with respect to the IGS station Polyhedron of about 200 stations atthe mm/ppb level (IGS orbits/ERP and station positions can be fixed even for
baselines 2000 km and longer). No need for precise satellite clocks (nearly
eliminated)
Absolute, precise point positioning ppp) worldwide, with respect to the IGSReference Frame IGS orbit/clocks/ERP held fixed) at mm precision level
Absolute, precise point navigation worldwide (ground, air, LEO satellites - no basestations needed ), at a cm precision level
Global Change Monitoring: solid Earth, atmosphere and oceans
ERP monitoring
plate motion and crustal deformation monitoring, volcanoes, etc.
monitoring of atmosphere (troposphere and ionosphere)
Precise time and freq. transfers (future contributions to UTC)
-
8/10/2019 Products IGS
13/29
Relative Positioning
Relative position precision at ppb/mm
IGS Orbits, ERP, base station position solutions can be held fixed at the IGS
solutions for all, even extreme, baseline lengths at ppb/mm precision level (in
ITRF insensitive to ERP)
When using double differencing, potentially more robust (than precise point
positioning), the IGS products ease data cleaning, ambiguity fixing
Complete covariance/correlation matrix available (e.g. for in SINEX format)
Suitable for continental, regional, national ITRF densification (e.g. EUREF -
normal equation matrix stacking of RNAAC SINEX solutions)
Warning: fixing IGS orbits/ERP implies very precise reference orientation and scale
even for (SINEX) unconstrained solutions (I.e. no stations fixed)
For long baselines (~ 1000km) ITRF orientation/scale changes need to be taken into
account prior normal matrix stacking
Insensitive to incompatibilities and clock errors
Insensitive to clock errors and all small (cm) ITRF changes for baselines
-
8/10/2019 Products IGS
14/29
Relative Positioning
Relative Positioning Rrequirements for cm Precision ( double differenced phase data with, or without phase
ambiguity fixing ; ~ 1 h occupancy)
IGS Products/ Baseline < 10 km 10 100 km 100 1000 km >1000 km
IGS Orbits No (Broadcast) IGS Rapid IGS Rapid/Final IGS Final
IGS ERP**** No No No NoIGS Sat Clocks No No No IGS Rapid/Final
IGS Iono Delays IGS iono* IGS iono* No** No**
IGS Tropo Delays Nominal/IGS tropo IGS tropo/ estimate Estimate Estimate
IGS ITRF Trasform No No No Yes
ERROR MODELS
IGS Ant phase center No Yes*** Yes*** Yes
Solid Earth tides No No Yes Yes
Ocean loading No No Yes YesRelativity correction No No Yes Yes
Sat phase wind up No No No Yes
Single frequency data; ** Two frequency data; *** For different antenna types only;
**** IGS ERP implied by IGS Orbits
-
8/10/2019 Products IGS
15/29
Precise Point Positioning
IGS combined Orbits, clocks held fixed in single point solutions
Equivalent to back substitution into complex, global (IGS) solutions
An efficient, flexible and convenient interface/access to the IGS reference frame
mm precision level for static point positioning worldwide, no base (IGSPolyhedron) station positions/data required
cm precision level for (epoch by epoch, ground, air, LEO sarellite) navigation, no
base (DGPS) station positions/data required.
Efficient and precise solutions for station clocks and tropospheric ZPDs
Disadvantages (wrt to double differencing/relative positioning)
More difficult to clean/edit data and/or to fix integer phase ambiguities
Sensitive to clock errors and to incompatibilities (see below) and even small
reference (ITRF) changes; orbits/clocks/ERP must be consistent
Correlation/variance matrix (amongst stations) lost and not available, thus not
well suited for national/continental ITRF (SINEX) densification
-
8/10/2019 Products IGS
16/29
Precise Point Positioning
Static Point Positioning Requirements (undifferenced phase/pseudorange data; < 1 h occupancy)
IGS Products/precision < 1 cm 1 10 cm 10 100 cm >100 cm
IGS Orbits IGS Final IGS Rapid/Final IGS Rapid/UltraR No (Broadcast)
IGS ERP*** No No No No
IGS Sat Clocks IGS Final IGS Rapid/Final IGS Rapid/UltraR No (Broadcast)
IGS Iono Delays No** No** IGS iono* IGS iono*
IGS Tropo Delays Estimate Estimate/IGS tropo IGS tropo/estimate Standard/nominalIGS ITRF Trasform Yes No No No
ERROR MODELS
IGS Ant phase centre Yes Yes No No
Solid Earth tides Yes Yes Yes No
Ocean loading Yes Yes No No
Relativity corrections Yes Yes Yes Yes
Sat phase wind up Yes Yes No No
* Single frequency data; ** Two frequency data; *** IGS ERP implied by IGS Orbits
Note:in near future,the Ultra Rapid IGS orbits (Ultra R )
-
8/10/2019 Products IGS
17/29
Precise Point Positioning (PPP)
-
8/10/2019 Products IGS
18/29
Precise Navigation
Navigation/Kinematic Point Positioning Requirements (undifferenced phase and pseudorange data;
instantaneous occupancy)
IGS Products/ precision < 10 cm 1050 cm 50500 cm >500 cm
IGS Orbits IGS Final IGS Rapid/Final IGS Rapid/Final No (Broadcast)
IGS ERP *** No No No No
IGS Sat Clocks IGS Final IGS Rapid/Final IGS Rapid/Final No (Broadcast)
IGS Iono Delays No** No** IGS iono* IGS iono*
IGS Tropo Delays Estimate Estimate/IGS tropo IGS tropo/estimate Standard/nominal
IGS ITRF Trasform Yes No No No
ERROR MODELS
IGS Ant phase centre Yes No No NoSolid Earth tides Yes Yes No No
Ocean loading Yes No No No
Relativity corrections Yes Yes Yes No
Sat phase wind up Yes No No No
* Single frequency data; ** Two frequency data *** IGS ERP implied by IGS Orbits
-
8/10/2019 Products IGS
19/29
-
8/10/2019 Products IGS
20/29
Compatibility
IGS CORE products (orbits/clock/ERP/stations)
Mutually compatible and consistent since Dec 1998
Consistency of orbits and clocks is of utmost importance for precise point positioning
IGS station (SINEX) solutions are compatible/consistent with IGS antenna offsets (station logfiles) and the antenna calibration (phase center) tables (IGS_01.pcv) at IGSCB Archives
IGS satellite clock solutions are based on/compatible with the following
assumptions/conventions:
Periodical special relativistic correction : - 2 . X .V/c2 applied
Cross correlation type of pseudoranges : C/A; P2= C/A + P2-P1)
: P1, P2 (After April 2, 2000, Wk 1056)
Adopted satellite antenna offsets (X,Y,Z m)
Block II/IIA : 0.279 0.000 1.023 (in the satellite fixed frame)
Block IIR : 0.000 0.000 0.000
no L1-L2 satellite/receiver calibration delayed applied
Ionospheric TEC grid maps, satellite/receiver calibration biases must be of the same solutions
and
corresponding mapping function and DCBs must be used for all ionospheric applications to derive
slant ionospheric delays)
-
8/10/2019 Products IGS
21/29
Compatibility
Solid Earth tides have once and twice daily periods; can reach up to 300 mm in height and
up to 50 mm in latitude and longitude.
-
8/10/2019 Products IGS
22/29
Compatibility
Ocean Loading Effects have once and twice daily periods; can reach up to 50 mm in height
and up to 10 mm in latitude and longitude.
-
8/10/2019 Products IGS
23/29
Scientific Applications
Earth Orientation Parameter (EOP) monitoring
IGS Polar Motion rates of unprecendeted precision (0.1 mas/day) and resolution
(1 day, or even 2 hours for CODE AC solutions )
Continuously available with delays of less than 24h (IGS Rapid)
Independent short period (
-
8/10/2019 Products IGS
24/29
Scientific Applications
Correlation between Polar Motion Rates (Xrt, Yrt (not shown)) and OAM+AAM is nearly always better
than 0.8 (except for the low signal period at or below 0.25 mas/d)
-
8/10/2019 Products IGS
25/29
Water Vapor Estimates Comparison
at Station Potsdam
Partial Water Vapor (PWV) from GPS at IGS station POTS (Germany) agrees with
Water Vapor Radiometer (WVR), well within one mm (Courtesy of GFZ).
-
8/10/2019 Products IGS
26/29
Limitations and Solutions
IGS Combined Orbits :
In 24 h files with 15 min sampling (0-23:45 GPS time); can be easilyconcatenated to span daily boundaries; easily be fitted with low order
polynomials for continuous representation
Small daily discontinuities (at the dm level)
Possible orbit origin offsets (biases at the cm level)
Improvements at the AC level, I.e. smaller daily AC orbit discontinuities
(
-
8/10/2019 Products IGS
27/29
Recent Changes and Improvements
IGS Preliminary SINEX Combined Products became official
From Feb 20/00 (GPS Week 1050), aligned to ITRF97 ( using min. constraints)
SeeIGS Mail 2740
for more details
New IGS ITRF97 realization (through the IGS SINEX combined solution
IGS00P04.snx
product)
From Feb 27/00 (GPS Week 1051); delay increased from 10 to 12 days
Improved ITRF97 realization for the IGS Final orbits/ERP/clocks
No noticeable changes to the IGS users (no transformation, no steps )
SeeIGS Mail 2750
and
2751
for more details
New Pseudorange bias convention
starts on Apr 02/00(wk 1056)
P1, P2replace the current convention: C/A, P2= C/A + (P2-P1)
Important forIGS clock users (precise point positioning, time transfers)
SeeIGS Mail 2744
for more details and the adopted C/A-P1 biases
IGS Ultra-Rapid Comb. Orbits/clocks
testing started Mar 2/00
-
8/10/2019 Products IGS
28/29
Future Developments
Improved IGS ITRF realization (see the next presentation)
Weekly, Preliminary SINEX combinations, official since Feb 20, 2000
Up to 250 IGS Polyhedron stations IGS Combined SINEX solutions
Continuous plate motion monitoring/quality check (under way)
Ultra Rapid products Pilot Project (
-
8/10/2019 Products IGS
29/29
QUESTIONS?
Jan Kouba
Geodetic Survey Division
Natural Resources Canada (NRCan)
615 Booth Street
Ottawa, Canada K1A OE9
Tim Springer (The IGS AC Coordinator)
Astronomical Institute, Univ. Bern
For details on IGS Products, see the IGS Annual Reports
http://igscb.jpl.nasa.gov/overview/pub.html