Modeling Errors in gps vertical Estimates Signal propagation effects


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Modeling Errors in GPS Vertical Estimates






Modeling Errors in GPS Vertical Estimates

  • Signal propagation effects

    • Signal scattering ( antenna phase center/multipath )
    • Atmospheric delay ( parameterization, mapping functions )
  • Unmodeled motions of the station

    • Monument instability
    • Loading of the crust by atmosphere, oceans, and surface water












Modeling Errors in GPS Vertical Estimates

  • Signal propagation effects

    • Signal scattering ( antenna phase center/multipath )
    • Atmospheric delay ( parameterization, mapping functions )
  • Unmodeled motions of the station

    • Monument instability
    • Loading of the crust by atmosphere, oceans, and surface water










Percent difference (red) between hydrostatic and wet mapping functions for a high latitude (dav1) and mid-latitude site (nlib). Blue shows percentage of observations at each elevation angle. From Tregoning and Herring [2006].



Difference between a) surface pressure derived from “standard” sea level pressure and the mean surface pressure derived from the GPT model. b) station heights using the two sources of a priori pressure. c) Relation between a priori pressure differences and height differences. Elevation-dependent weighting was used in the GPS analysis with a minimum elevation angle of 7 deg.



Height (red: simulated; black: estimated) and ZTD (green: simulated; blue: estimated) errors versus latitude as a function of error in surface pressure used to calculate the a priori ZHD. Uniform 10 mm data weighting applied.



Height (black/blue) and ZTD (red/green) errors at Davis, Antarctica, for different elevation cutoff angles as a function of error in surface pressure used to calculate the a priori ZHD.. Results shown for both elevation-dependent (blue and red results) and constant data weighting (black and green).



Modeling Errors in GPS Vertical Estimates

  • Signal propagation effects

    • Signal scattering ( antenna phase center/multipath )
    • Atmospheric delay ( parameterization, mapping functions )
  • Unmodeled motions of the station

    • Monument instability
    • Loading of the crust by atmosphere, oceans, and surface water




Modeling Errors in GPS Vertical Estimates

  • Signal propagation effects

    • Signal scattering ( antenna phase center/multipath )
    • Atmospheric delay ( parameterization, mapping functions )
  • Unmodeled motions of the station

    • Monument instability
    • Loading of the crust by atmosphere, oceans, and surface water














Differences in GPS estimates of ZTD at Algonquin, Ny Alessund, Wettzell and Westford computed using static or observed surface pressure to derive the a priori. (Elevation-dependent weighting used).



Station height estimates for Rio Grande, Argentina, using pressure from height-corrected STP, GPT and actual observations (MET). Dashed black line shows observed surface pressure; pink line shows atmospheric pressure loading deformation (corrected for in the GPS analyses) , offset by 2.07 m.




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