Simulation and Prediction Module

For the prediction of the system performance and for the design and dimensioning of the GNSS Services, a simulation/prediction function is implemented in GalTeC. For this purpose, the NavPos Systems Service Volume Simulator AVIGA® has been developed into a GalTeC Prediction tool in the frame of the GalTeC project. The Prediction Tool offers the means to predict, analyse and evaluate future Galileo services, such as the Commercial Services.

The Simulation Module offers to run simulations at a specific point, over a specific area and along routes in order to analyse Accuracy, Continuity of Service, Integrity and Availability.

In addition, the Simulation Module supports the analysis of the GNSS Constellation's Visibility and Geometry performances.

This module is composed of following components:

• Space Segment Module: Which predicts satellite trajectories from standard almanacs, such as Almanac YUMA files, computes satellite trajectories from user defined Keplerian elements; Broadcast Ephemeris or SP3 Precise Ephemeris.
• Visibility Module: Evaluates visibility characteristics of satellite coverage accounting for mask skyline angles;
• DOP (or Geometry) Module: Evaluates Dilution of Precision (DOP) and Position Error characteristics of satellite coverage. Position accuracy is estimated from the position errors covariance matrix.
• Availability Module: Evaluates availability of DOP and position accuracy. Models of satellite outages and navigation solution errors are used in this module.
• Integrity/Continuity Modules:
  • RAIM: Evaluates availability of the snapshot RAIM FD/FDE methods.
  • SBAS: Evaluates availability of the SBAS Protection Levels.
  • Galileo: Evaluates availability of protection level according to concept proposed for Galileo system, calculates the associated Integrity Risk.
• Service Availability module: Analyses availability of Accuracy, Continuity and Integrity Risk according to the proposed Galileo concept. It also gives analysis of critical satellites.
• GBAS / Galileo LE: Analyses performance of GPS and Galileo based local area augmentation systems.
• Route Module: Analyses the performance along a specified route
• SISE Analysis Module: Assesses satellite orbital and clock errors from SP3 precision orbits and RINEX Navigation files.
• Data Dissemination Module: Simulates dissemination of Galileo Messages from Ground Mission Segment via ULS network to world-wide or regional users (under development).

Some of the components include "error components simulation" to analyse the Galileo Service performance with the impact of various sources of errors. The prediction of the Galileo Services according to their specification, and also with further parameter settings, is done with the GalTeC Prediction Tool. The tool allows the simulation of rare system failures such as erroneous behaviour and outages.

The figure below shows, as an example, the global Galileo SOL service availability for a period of 10 days.