The integrated use of GPS/GLONASS observations in network code differential positioning

We present the methodology and results of GPS/GLONASS integration in network code differential positioning for regional coverage across Poland using single frequency. Previous studies have only concerned the GPS system and relatively short distances to reference stations of up to tens of kilometers. This study is limited to using GPS and GLONASS. However, the methodology presented applies to all satellite navigation systems. The deterministic and stochastic models, as well as the most important issues in GPS/GLONASS integration are discussed. Two weeks of the GNSS observations were processed using software developed by the first author. In addition to interpolation of pseudorange corrections (PRCs) within the polygon of reference stations, the effect of their extrapolation outside that polygon is also briefly presented. It is well known that the positioning accuracy in a network of heterogeneous receivers can be degraded by GLONASS–FDMA frequency-dependent hardware biases. Our research reveals that when using such networks, the effect of these biases on the network differential GNSS (NDGNSS) positioning results as derived from both GPS and GLONASS can be reduced by simple down-weighting of GLONASS observations. We found that the same approach for the homogeneous equipment is not required; however, it can enhance performance of NDGNSS. Yet, the addition of the down-weighted GLONASS pseudoranges still improves the positioning accuracy by 14–25 %. The representative NDGNSS estimation is characterized by 0.17, 0.12 and 0.32 m RMS errors for the north, east and up component, respectively

Nurses' perceptions of aids and obstacles to the provision of optimal end of life care in ICU

Contains fulltext : 172380.pdf (publisher's version ) (Open Access

Initial analysis of the tracking performance of the GOOSE GNSS Software-Defined Receiver

The GOOSE (GNSS Receiver with open software interface) Software-Defined Receiver has been developed at the Fraunhofer Institute for Integrated Circuits (IIS) in Nürnberg, Germany. The main motivation for the development of this platform was to control the receiver at all stages, from digital signal processing to the PVT domain, and to enable controlled feedback to the hardware. Besides having access to all raw data including correlation values, the GOOSE receiver also enables for example tight- or ultra-tight integration with an inertial navigation system or other dead reckoning systems, as these kinds of architectures require access to the acquisition and tracking loops. In this paper, the tracking performance of the GOOSE platform was evaluated and compared to a reference receiver (Septentrio PolaRx5S). Several long data sessions were recorded on a “zero baseline” in which both receivers used the same precise geodetic antenna that was also developed at Fraunhofer IIS. The measurements were performed in a harsh environment (obstructions, multipath, possible interferences), as well as on a site with an unobstructed sky view. Quality and performance analyses were performed using raw measurements (in the domain of primary observables) of three civil GPS signals: L1CA, L2CM, and L5. The data were processed using the “zeroEdit” module of the TUB-NavSolutions academic software for education and research. The quality of the raw observables and tracking performance were described by the following parameters: number of cycle slips detected, number of un-correctable cycle slips, number of loss of locks of the signals, number of single epoch data gaps, and the length of carrier phase arcs. The presentation is illustrated with some numerical examples

Performance comparison of ionospheric models used for GNSS positioning

An evaluation of applicability of ionospheric corrections derived from the two global total electron content (TEC) maps, Neustrelitz DLR/GIM and Center for Orbit Determination in Europe CODE/GIM, for mitigation of ionospheric threads in precise GNSS positioning, has been done. Investigations on the both models have been performed in the following empirical approach. Investigation in the domain of coordinates: Processing of selected static GPS data in relative pseudo-kinematic mode, taking ionospheric corrections from the two selected models, to solve for position at every observational epoch. Comparison of the obtained results (time series of coordinates) with precise reference coordinates of the station calculated over a long time period. Investigation in the domain of TEC corrections: Preparation of two time series of interpolated TEC values for the all observation epochs using the CODE- and DLR maps, and calculation of TEC time series from the recorded GPS observations. Comparison and analysis of the all three sets of TEC values. Calculation of the Rate of TEC (ROT) and of scintillation index S4 as indicators of ionospheric irregularities. Analysis of the time series of TEC, ROT, S4 and the pseudo-kinematic station coordinates to detect and identify origin of anomalous signals. Experimental GPS data from the continuously operated station at Kiruna (Sweden) located at the polar region, and Wettzell (Germany)located at mid latitude, have been processed. The paper presents first results of investigations on GPS data recorded during a quiet period and under the presence of ionospheric irregularities. Further investigations are in progress