Using the Global Navigation Satellite System and satellite altimetry for combined Global Ionosphere Maps

Within this study we create Global Ionosphere Maps (GIM) from GNSS data and additionally introduce satellite altimetry observations, which help to compensate the insufficient GNSS coverage of the oceans. The obtained global maps are in 2 h intervals and daily values of Differential Code Biases (DCB) for all the GNSS satellites and receivers are also estimated. The combination of the data from around 160 GNSS stations and two satellite altimetry missions - Jason-1 and TOPEX/Poseidon - is performed on the normal equation level. The comparison between the integrated ionosphere models and the GNSS-only maps shows a higher accuracy of the combined GIM over the seas. The study aims at improved combined global TEC maps, which should make best use of the advantages of each particular type of data and have higher accuracy and reliability than the results derived by the two methods if treated individually.