230 likes | 256 Views
This research outlines the development of a regional ionosphere model in Norway using GPS data from SATREFTM stations to enhance navigation in the Arctic region. The model's performance was verified against the IGS GIM and compared with the EGNOS ionosphere model, showing promising results. Future work includes real-time implementation and further improvements. Acknowledgments: The project was supported by the Norwegian Space Centre and benefited from valuable discussions with experts at the Norwegian University of Life Sciences.
E N D
A Norwegian Ionosphere Model Based on GPS Data Anna B.O. Jensen Nordic Institute of Navigation Oslo, June 2008
Outline • Navigation in the arctic • Ionospheric activity at high latitudes • SATREFTM Ionosphere Model • Verification towards IGS GIM • Comparison with EGNOS ionosphere model • Summary
Navigation in the arctic (1) • Norway is located at high latitudes, from 60° to 80° N, mainly in the arctic region • GPS is used extensively as a navigational mean in the arctic • Unfortunately, GNSS performance is limited in the arctic compared to mid latitudes
Navigation in the arctic (2) • Much offshore activity in the Norwegian Sea • Need for reliable navigation • In the future: • Increasing activity and more traffic due to global warming and more oil and gas exploration • Increasing need for navigation
Ionospheric activity at high latitudes • At high latitudes characteristics of the ionospheric activity are different than at mid latitudes: • Higher ionospheric variability • Increased amount of scintillation • This does affect navigation users e.g. by: • Reduced accuracy • Poor signal tracking (loss of lock)
Ionospheric activity at high latitudes Feb. 28, 2008 70°N network 60°N network Trimble gpsnet software
SATREFTM Ionosphere Model (1) • Several ionosphere models exist, but they are generally poor for high latitudes • In 2007 the NMA therefore started development of a regional Norwegian ionosphere model based on the SATREFTM network of GNSS stations
SATREFTM Ionosphere Model (2) • The model is based on: • GPS data from selected SATREFTM stations • Estimation of ionospheric delays in the stations • Spatial interpolation to obtain nationwide grid model
Verification towards GIM (1) • Verification with respect to the Global Ionosphere Model (GIM) of the IGS • IONEX files retrieved from the IGS web site, and L1 ionosphere delays extracted for comparison with SATREFTM Ionosphere Model • 20 grid points used for verification
Verification towards GIM (2) • Differences, SATREFTM minus IGS GIM • 30 second sampling, 20 grid points
Verification towards GIM (3) • Summing up: • Mean of differences of 2 - 5 cm is basically negligible • Indicates no offset between the two models • Standard deviation of 12 – 19 cm • Occur mainly because no filtering is applied to the SATREFTM model • Lower standard deviation on the day with low ionospheric activity
Comparison with the EGNOS iono. model • Verification of the SATREFTM model towards the IGS GIM showed acceptable results • Therefore, the SATREFTM model is now used for a preliminary evaluation of the performance of the EGNOS ionosphere model in the arctic
Comparison with EGNOS iono. model • Differences, SATREFTM minus EGNOS • 16 grid points
Selected grid point – Feb. 28, 2008 • EGNOS: blue, GIM: green, SATREFTM: red • EGNOS model is biased
Selected grid points – Feb. 28, 2008 • EGNOS bias for upper grid point
Selected grid points – Feb. 2, 2008 • Another day - again EGNOS bias for same point
Future work • Modify model to run in real time • Lots of programming • Further investigations to decide on: • Coverage area • Grid spacing • Number of SATREFTM stations to include • Temporal update interval • Information to users – web application
Summary • Development of the SATREFTM Ionosphere Model has been initiated • Verification of the SATREFTM Ionosphere Model towards the IGS GIM show very good results • Comparison with EGNOS model show deviations for some grid points • Improvement expected with new EGNOS version this summer
Acknowledgments • Thanks to the Norwegian Space Centre for providing support for the work • Thanks to Ola Øvstedal, Norwegian University of Life Sciences in Ås, for valuable discussions during the development phase