This research evaluates the potential benefits of the tightly combined processing of a global navigation satellite system together with the additional ranging observations from a satellite based augmentation system. In specific, the experiment presents performance of precise instantaneous single-frequency positioning based on European Galileo and EGNOS navigation systems. Due to currently low number of Galileo satellites, the test observational data were obtained with hardware GNSS signal simulator. All calculations were performed with in-house developed software - GINPOS. The results show that it is possible to obtain improvement in the accuracy and reliability of single-frequency precise positioning when including observations from SBAS systems. However, one must take in to account that at middle latitudes EGNOS satellites are observed at low elevations what results in higher atmospheric errors affecting its signals., Jacek Paziewski, Paweł Wielgosz and Marta Krukowksa., and Obsahuje bibliografické odkazy
The paper presents the foundations of MAFA method, as well as its application to the pro cessing of new GPS and Galileo signals. The presented numerical tests have been carried out on the basis of data obtained from a hardware GNSS signal simulator as there are currently too few Galileo satellites on orbit. In the proposed methodology, first linear combinations have been formed using new GNSS signals. These linear combinations constitute a data set for a cascade adjustmen talgorithm employing extended MAFA method. Feasibility of a single-epoch precise positioning has been tested. The single-epoch positioning is particularly important for reliable real-time landslide and deformation monitoring. The obtained test results show a high success rate of the extended MAFA method. The number of the correct single-epoch solutions varied from 85 % to over 99 % depending on the baseline length and accuracy of an a priori position. Thus, the MAFA method may be successfully used with new GPS and Galileo signals, even for the processing of single-epoch data., Sławomir Cellmer, Jacek Paziewski and Paweł Wielgosz., and Obsahuje bibliografické odkazy
GPS (Global Positioning System) technique has become a major tool in contemporary surveying and geodesy. This concerns mostly measurements of horizontal point coordinates, where centimeter-level accuracies are usually required and easily achievable. For the height component, however, these requirements are higher and millimeter-level accuracy is necessary. On the other hand, the intrinsic precision of GPS-derived heights is clearly lower comparing to the horizontal components. This is due to unfavorable satellite geometry, adverse effects of the troposphere or GPS antenna phase center offset and variations. In order to overcome these effects one has to carefully model all the error sources and rigorously process the GPS data. This paper presents studies on the optimal GPS data processing strategy suitable for precise leveling. This was done through the extensive testing and selection of the most appropriate observational session duration, ambiguity resolution strategy, network geometry, troposphere and ionospheric delay reduction methods, signal linear co mbination, elevation angle cut-off, etc. The analyzed processing strategies were evaluated through the processing of a test network. The test network consisted of 19 monitored points and 5 control points, and covered the area of 20 km x 60 km. The obtained results show that the precise GPS leveling with the selected optimal processing strategy allows for about 3 mm repeatability of height measurements when processing 4-hour long sessions. In our opinion GPS leveling may serve as fast and cost-effective replacement of classic geometric leveling, especially in applications where the hei ghts in orthometric or normal height systems are not necessary. This is the case in, e.g., ground deformation studies., Katarzyna Stepniak, Radosław Baryła, Paweł Wielgosz and Grzegorz Kurpinski., and Obsahuje bibliografické odkazy