Prologue to High-Precision GPS Data Analysis: Towards a typical dialect for the workshop

Introduction to high precision gps data analysis towards a common language for the workshop
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Slide 1

Prologue to High-Precision GPS Data Analysis: Towards a typical dialect for the workshop

Slide 2

Topics to be Covered in the Workshop Wednesday Morning Introduction to GPS Data Analysis Automatic Processing utilizing sh_gamit and sh_glred What's New in GAMIT/GLOBK Wednesday Afternoon Reference Frames and Spatial Filtering Effective Use of GLOBK Thursday Morning Estimating Heights and Atmospheric Parameters An Approach to Error Analysis Thursday Afternoon Overview of Kinematic Processing with Track A Short Introduction to Block Modeling GAMIT/GLOBK Utilities

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Your area is: 37 o 23.323' N 122 o 02.162' W Instantaneous situating with GPS Instantaneous Positioning with Pseudoranges Receiver arrangement or sh_rx2apr Point position ( svpos ) 30-100 m Differential ( svdiff ) 3-10 m

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High-exactness situating utilizes the stage perceptions • Long-session static: change in stage over the long run conveys a large portion of the data • Repairing cycle slips is thusly vital • The shorter the occupation, the more imperative is general uncertainty determination Each Satellite (and station) has an alternate mark

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Accuracy of Single-pattern Observations as a Function of Session Length Horizontal Vertical Agreement in mm of single session with normal of 30 24-h sessions for three distinctive reference stations at 30, 200, and 500 km Firuzabadi & King [2009]

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Horizonal (mm) Accuracy of Network Observations as a Function of Session Length Bottom names are diverse reference systems (3-20 destinations) with greatest degree in km Vertical (mm) Firuzabadi & King [2009]

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Observables in Data Processing Fundamental perceptions L1 stage = f1 x extend (19 cm) L2 stage = f2 x run (24 cm) C1 or P1 pseudorange utilized independently to get recipient clock counterbalance (time) To gauge parameters utilize doubly differenced LC = 2.5 L1 - 2.0 L2 "without ionosphere blend" Double differencing expels clock vacillations; LC evacuates all of ionosphere Both DD and LC open up clamor (utilize L1, L2 specifically for baselines < 1 km) Auxiliary mixes for information altering and vagueness determination "sans geometry mix" or "Additional wide-path" (EX-WL) (86 cm) LG = L2 - f2/f1 L1 Removes all recurrence autonomous impacts (geometric & climate) yet not multipath or ionosphere N2 - N1 "Widelane ambiguities" (86 cm); if stage just, incorporates ionosphere Melbourne-Wubbena wide-Lane (86 cm): stage/pseudorange mix that evacuates geometry and ionosphere; ruled by pseudorange commotion

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Modeling the Observations I. Applied/Quantitative Motion of the satellites Earth's gravity field ( leveling 10 km; higher sounds 100 m ) Attraction of Moon and Sun ( 100 m ) Solar radiation weight ( 20 m ) Motion of the Earth Irregular turn of the Earth ( 5 m ) Luni-sun based strong Earth tides ( 30 cm ) Loading because of the seas, air, and surface water and ice ( 10 mm) Propagation of the flag Neutral air ( dry 6 m; wet 1 m ) Ionosphere ( 10 m however crosses out to few mm more often than not ) Variations in the stage focuses of the ground and satellite radio wires ( 10 cm) * not entirely demonstrated

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Modeling the Observations II. Programming Structure Satellite circle IGS organized ephemeris (Earth-settled SP3 document) [ track ] GAMIT classified ephemeris ( t-record ): numerical mix by circular segment in inertial space, fit to SP3 record, might be spoken to by its underlying conditions (ICs) and radiation-weight parameters; requires arranged places of Sun and Moon Motion of the Earth in inertial space [ model or track ] Analytical models for precession and nutation (classified); IERS watched values for shaft position (wobble), and pivotal turn (UT1) Analytical model of strong Earth tides; worldwide frameworks of sea and climatic tidal stacking Propagation of the flag [ model or track ] Zenith hydrostatic (dry) delay (ZHD) from weight ( met-record, VMF1, or GPT ) Zenith wet deferral (ZWD) [crudely demonstrated and assessed in illuminate or track ] ZHD and ZWD mapped to viewable pathway with mapping capacities (VMF1 lattice or GMT) Variations in the stage focuses of the ground and satetellite reception apparatuses (ANTEX record)

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Parameter Estimation Phase perceptions [ comprehend or track ] Form twofold contrast LC mix of L1 and L2 to scratch off tickers & ionosphere Apply from the earlier limitations Estimate the directions, ZTD, and genuine esteemed ambiguities Form M-W WL as well as stage WL with ionospheric imperatives to gauge and resolve the WL (L2-L1) whole number ambiguities [ autcln, unravel, track ] Estimate and resolve the thin path (NL) ambiguities Estimate the directions and ZTD with WL and NL ambiguities altered - Estimation can be group slightest squares [ explain ] or consecutive (Kalman channel [ track ] Quasi-perceptions from stage arrangement (h-record) [ globk ] Sequential (Kalman channel) Epoch-by-age trial of similarity (chi2 increase) however cluster yield

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Limits of GPS Accuracy Signal proliferation impacts Signal disseminating ( recieving wire stage focus/multipath ) Atmospheric postponement (essentially water vapor) Ionospheric impacts Receiver clamor Unmodeled movements of the station Monument precariousness Loading of the outside by environment, seas, and surface water Unmodeled movements of the satellites Reference outline

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Limits of GPS Accuracy Signal engendering impacts Signal diffusing ( radio wire stage focus/multipath ) Atmospheric deferral (mostly water vapor) Ionospheric impacts Receiver commotion Unmodeled movements of the station Monument shakiness Loading of the covering by air, seas, and surface water Unmodeled movements of the satellites Reference outline

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Reflected Signal Direct Signal Reflected Signal Mitigating Multipath Errors Avoid Reflective Surfaces Use a Ground Plane Antenna Use Multipath Rejection Receiver Observe for a long time Remove with normal from numerous days

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Multipath and Water Vapor Effects in the Observations One-way (undifferenced) LC stage residuals anticipated onto the sky in 4-hr previews. Spatially repeatable commotion is multipath; time-changing clamor is water vapor. Red is satellite track. Yellow and green positive and negative residuals only for visual impact. Red bar is scale (10 mm).

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Limits of GPS Accuracy Signal proliferation impacts Signal dissipating ( recieving wire stage focus/multipath ) Atmospheric postponement (for the most part water vapor) Ionospheric impacts Receiver commotion Unmodeled movements of the station Monument flimsiness Loading of the outside layer by air, seas, and surface water Unmodeled movements of the satellites Reference outline

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Monuments Anchored to Bedrock are Critical for Tectonic Studies (less for climatic concentrates) Good tying down: Pin in strong shake Drill-propped (left) in cracked shake Low working with profound establishment not great securing: Vertical poles Buildings with shallow establishment Towers or tall building (warm impacts)

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Annual Component of Vertical Loading Atmosphere (purple) 2-5 mm Snow/water (blue) 2-10 mm Nontidal sea (red) 2-3 mm From Dong et al. J . Geophys. Res., 107 , 2075, 2002

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24-hr position gauges more than 3 months for station in semi-parched eastern Oregon Random clamor is ~1 mm flat, 3 mm vertical, however the vertical has ~10-level systematics enduring 10-30 days which are likely a blend of landmark insecurity and environmental and hydrologic stacking

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Limits of GPS Accuracy Signal proliferation impacts Signal scrambling ( radio wire stage focus/multipath ) Atmospheric postponement (principally water vapor) Ionospheric impacts Receiver commotion Unmodeled movements of the station Monument flimsiness Loading of the outside by air, seas, and surface water Unmodeled movements of the satellites Reference outline

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GPS Satellite Limits to model are non-gravitational increasing velocities because of sun based and albedo radiation, lopsided pushes, and outgassing; and non-circular recieving wire design

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Quality of IGS Final Orbits 1994-2008 20 mm = 1 ppb Source: http://acc.igs.org

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Quality of ongoing expectations from IGS Ultra-Rapid circles 2001-2008 20 mm = 1 ppb Source: http://acc.igs.org

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Limits of GPS Accuracy Signal engendering impacts Signal dissipating ( reception apparatus stage focus/multipath ) Atmospheric deferral (for the most part water vapor) Ionospheric impacts Receiver commotion Unmodeled movements of the station Monument shakiness Loading of the hull by air, seas, and surface water Unmodeled movements of the satellites Reference outline

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Reference Frames Global Center of Mass ~ 30 mm ITRF ~ 2 mm, < 1 mm/yr Continental < 1 mm/yr horiz., 2 mm/yr vert. Nearby - might act naturally characterized

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Effect of Orbital and Geocentric Position Error/Uncertainty High-accuracy GPS is basically relative ! Gauge mistake/vulnerability ~ Baseline separate x geocentric SV or position blunder SV height SV mistakes diminished by averaging: Baseline mistakes are ~ 0.2 • orbital mistake/20,000 km e.g. 20 mm orbital mistake = 0.2 ppb or 0.2 mm on 1000 km pattern Network position blunders amplified for short sessions e.g. 5 mm position blunder ~ 1 ppb or 1 mm on 1000 km pattern 10 cm position mistake ~ 20 ppb or 1 mm on 50 km benchmark

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