GALOCAD User interface

Report (2008)

Galileo Local Component for the detection of atmospheric threats

in Goodman, John (Ed.) Proceedings of the 12th International Ionospheric Effects Symposium (IES2008) (2008, May)

A novel method for the quantitative assessment of the ionosphere effect on high accuracy GNSS applications which require ambiguity resolution

in Journal of Atmospheric & Solar-Terrestrial Physics (2008), 70

Characterization of the tropospheric small-scale activity

Report (2008)

Project Office - Final report

Report (2008)

Ionospheric Products and Services from the Regional Warning Centers of the International Space Environment Service (ISES) for GNSS Users

Conference (2008)

Total Electron Content monitoring using triple frequency GNSS data: a three-step approach

Conference (2008)

Ionosphere Modelling for GALILEO Single Frequency Users

Poster (2007, October 17)

Assessment of the NeQuick Model at Mid-latitudes using GPS TEC and Ionosonde Data

in First Colloquium Scientific and Fundamental Aspects of the Galileo Programme (2007, October)

The ionosphere plays a crucial role in Global Navigation Satellite Systems (GNSS) accuracy. In extreme cases, this electrically charged part of the atmosphere can lead to errors in positioning exceeding ... [more ▼]

The ionosphere plays a crucial role in Global Navigation Satellite Systems (GNSS) accuracy. In extreme cases, this electrically charged part of the atmosphere can lead to errors in positioning exceeding 100 $m$. At first approximation, ionospheric effects depend mainly on the total content in free electrons of the ionosphere ("total electron content", TEC). The modelling of the latter parameter reveals thus itself critical in particular for single frequency receivers, the most common ones constituting the mass market. In the framework of GALILEO, the NeQuick model has been chosen to this extent and will be integrated into a global algorithm providing the users with daily updated information. In order to reach the specified correction level, the model itself and its latest evolutions as well as its use for GALILEO are investigated. As a first step in a thorough analysis, we take benefit of ionosonde and GPS TEC data from the Dourbes Geophysical Observatory (Belgium) to study the mid-latitudes. Constraining the model with ionosonde measurements, we first investigate the difference between GPS-derived vertical TEC (vTEC) for Dourbes station and corresponding values from NeQuick for the latest years for solar maximum in 2002 and minimum in 2006. With this approach, we reach residual errors of about 20% RMS for 2002 and 30% for 2006. Through a focusing process, we identify then gradually best and worst months and days for which we observe the evolution between two versions of NeQuick. We highlight among others improvements from the latest modification in the topside formulation which appears clearly in the electron density profiles examined at the end of the assessment. [less ▲]

Statistical study of ionospheric small-scale irregularities at mid-latitudes using GPS measurements

Conference (2007, July 11)

At the present time, Global Navigation Satellite Systems (GNSS) allow to obtain a precision of a few centimeters in real time using positioning techniques like the so-called Real Time Kinematics (RTK ... [more ▼]

At the present time, Global Navigation Satellite Systems (GNSS) allow to obtain a precision of a few centimeters in real time using positioning techniques like the so-called Real Time Kinematics (RTK). Nowadays, the ionosphere remains the most important error source affecting such GNSS applications. Indeed, the presence of small-scale irregular structures in the Total Electron Content (TEC) can strongly affect the reliability and the precision of high precision real time positioning applications. Those small-scale structures can have several origins: Traveling Ionospheric Disturbances, "noise-like" variability in TEC, scintillations. The Royal Meteorological Institute of Belgium (RMI) has developed a software which allows to monitor the TEC using GPS measurements (at one station). The software can also be used to detect small-scale irregularities in TEC by monitoring TEC temporal gradients (i.e. rate of change). The RMI has applied this software to the GPS data collected at Brussels from April 1993 up to now what represents a period of more than a Solar Cycle. The results obtained from this GPS-TEC software will be presented. First, the paper analyzes the different types of small-scale structures which have been observed in TEC. Then, a statistical study of those ionospheric irregularities is presented; we shall analyze their probability of occurrence and their amplitude (in TECU/min) depending on daytime, season, solar activity, geomagnetic activity... The results of our study which is financed by the GNSS Supervising Authority will allow to have a better understanding of the usual case/worst case conditions encountered in high precision positioning applications based on GNSS. [less ▲]