Why Tefnut?

  • Meteorology: high spatio-temporal tropospheric parameters estimated at GNSS receivers, such as tropospheric path delays in zenith or slant directions, tropospheric horizontal gradients or derived indicators, are valuable for improvement of numerical weather forecasts and nowcasts
  • Climate: accurate long-term GNSS troposphere estimates are valuable for independent validation of climate models, water vapour cycle etc
  • Positioning: tropospheric corrections are provided from a local augmentation service for fast ambiguity resolution using PPP-RTK
  • G-Nut/Tefnut is a tool for advanced monitoring of the troposphere through analysing ground-based GNSS observations when supported with precise GNSS products.


  • Post-processing long-term troposphere monitoring (climate research)
  • Near real-time troposphere estimates (meteorology)
  • Real-time troposphere estimates (meteorology, PPP-RTK)
  • Stochastic modelling with a high temporal parameter resolution
  • Estimating zenith path delays and tropospheric horizontal gradients
  • Estimating slant tropospheric delays retrieved from carrier-phase post-fit residuals and trophospheric parameters
  • Troposphere state indicators (severe weather events)



  • Strategy: autonomous PPP for troposphere estimates
  • Estimators: Kalman filter, backward smoother
  • Modelling: compliant with the IERS 2010 standards
  • Multi-GNSS: GPS, GLONASS, Galileo, BeiDou
  • Observations: dual-frequency pseudoranges and carrier phases
  • Configuration: flexible command-line and XML-file configuration


  • Real-time: forward filter using data streams
  • Near real-time: filter+smoother using data streams or hourly files
  • Post-processing: filter+smoother using high-accuracy product
  • Network/station: parallel processing of stations
  • Static mode: reference stations platform


  • Bias SINEX files (differential code biases)
  • SINEX files (station meta data)
  • ATX files (antenna phase center offsets and variations)
  • BLQ files (ocean-tide loading station coefficients)
  • SP3 files (precise orbits) and RINEXC files (satellite clocks)
  • RINEX 2/3 files (observation and navigation data)
  • RTCM 3 streams (real-time data/products via NTRIP)


  • LOG file for common logging
  • PPP file for processing logging (individual stations)
  • FLT for results from forward filter (individual stations)
  • SMT for results from backward smoother (individual stations)
  • COST-716 file for estimated tropospheric products
  • SINEX_TRO v2 file for estimated tropospheric products


Latest releases

  • Tefnut Trial: 3.4
  • Tefnut Pro: 3.4
  • Tefnut Real-Time: 3.4

Software version

  • 30-day trial version (Trial)
  • Full functionality (Pro)
  • Full & Real-Time (Real-Time)


  • Linux (default distribution)
  • OSX (extra fee)
  • Windows (extra fee)

Pre-compiled binaries only.


Tefnut Trial

30-day trial version with a full functionality of G-Nut/Tefnut Pro & RT (Real-Time)

no fee

On request

Tefnut Pro

Commercial software for post-processing multi-GNSS PPP solution

from 3000 EUR

More information

Tefnut Real-Time

Commercial software for post-processing and real-time processing

from 4500 EUR

More information

The price is for a major release, for a consecutive update the price is reduced by 50%.
The price depends on number of stations.



A system designed for near real-time monitoring of GNSS tropospheric products (zenith tropospheric delays and linear horizontal gradients) and other related information. It consists of geographical views and time-series plots both supporting an interactive selection of data sources, parameter types, individual vs. combined views, setting of parameter ranges etc. Geographical plot animations and sortable numerical data tables then complete the system.



Basic usage and help instructions.


A detailed description of the software.

Individual support

Available on request. Contact us at

Support fee can be combined with a software fee.


The troposphere is the lower part of the atmosphere (approx below 12 km). Radio signals transmitted from GNSS satellites are banded and delayed by refractivity of the neutral atmosphere up to 60 km due to Fermat’s principle, and such delay needs to be considered in GNSS positioning. The so-called tropospheric effect on GNSS is theoretically divided into two parts: dry and wet, and hence the total tropospheric path delays split accordingly... (read more)