"G-Nut/Shu" is the end-user application designed to process Numerical Weather Model (NWM) data field in support of tropospheric augmentation corrections for GNSS positioning, navigation and timing. The application is implemented using the G-Nut core library developed at the Geodetic Obsevatory Pecny. G-Nut/Shu is the application for tropospheric and meteorology parameter derivation from the numerical weather (NWM) data field. The software is designed to support a flexible functionality (questions related to the software could be sent to This email address is being protected from spambots. You need JavaScript enabled to view it. - J.Dousa or M.Elias):

  • handle NWM products: ERA, WRF, ALADIN, HARMONIE, GFS (GRIB/NETCDF), parameters, coordinate systems, etc.,
  • calculate selected tropospheric and meteorological parameters for requested area (grid) or user location (GNSS stations),
  • support variants of temporal and spatial interpolation methods (linear/bi-linear/spline, vert2hor/hor2ver/integration {\ldots}),
  • apply different approaches for vertical parameter fitting (power/logarithmic, height-/pressure-dependent, {\ldots}),
  • use various ZWD surface calculations (integration, Askne-Nordius, GOP-ZWD/GOP-AN model variants,{\ldots}),
  • exploit variants of ZWD vertical scaling (GOP, RTCA-MOPS, {\ldots}),
  • model height-pressure relation using fixed/linear/zero T lapse rates,
  • refractivity coefficients (SW 1953, TH 1974, BV 1992, FO 1999, RU 2002),
  • densify original profile with a multiplication factor,
  • adjust surface parameters in vertical parameter approximations,
  • estimate tropospheric linear horizontal gradients from ZWD/ZHD grids,
  • estimate combination ratio between water vapour and ZWD decays.


  • Dousa J, Elias M (2014) An improved model for calculating tropospheric wet delay, Geophys. Res. Lett., 41, 4389–4397, doi:10.1002/2014GL060271.

Figures show selected parameters - pressure, partial water vapour pressure, zenith total and zenith wet delays - derived from the global NWM data fields in support

Example global pressure derived from the NWM by G-Nut/Shu software Example global WV pressure derived from the NWM by G-Nut/Shu software
Example global ZTD derived from the NWM by G-Nut/Shu software Example global ZWD derived from the NWM by G-Nut/Shu software