GNSS augmentation

About: GNSS augmentation is a research topic. Over the lifetime, 2478 publications have been published within this topic receiving 28513 citations. The topic is also known as: SBAS & Satellite Based Augmentation System.

A topological approach with MEMS in smartphones based on routing-graph

Abstract: GNSS (Global Navigation Satellite System) supported navigation with smartphones is an established technique. Solutions for position estimation for GNSS-shaded areas are developed more and more in the research field of the indoor navigation. The MEMS (MicroElectroMechanical Systems) sensors integrated into smartphones will be used increasingly for this. The aim of the research group at the HCU is the autonomous navigation only with MEMS sensors, favors are accelerometer, gyroscope and barometer. The quality of MEMS inertial sensors based position estimate decreases with time. Additional information should be used as support which is a prerequisite to realize a navigation application. A support is therefore possible with the available map data or the routing graph. In most approaches, the low-cost sensors are fused with the help of particle filter and Kalman filter at present. This serves the simple integration of external support, such as maps. In this work an approach without these filters is presented. A position estimate based on the routing nodes and edges shall be realized, only with the integrated MEMS inertial sensors in the smartphone. A fusion with further supports is not provided. The position estimate is calculated on the path network which is normally the basis for the routing to calculate the path. The position on a routing edge is derived from the acceleration sensors and the gyroscopes with step detection and orientation comparison. At a routing node, the sensor data is used to choose the probably nearest routing edge. For comparison purposes, approaches with Kalman filter and particle filter are applied to the same data set.

System and method for GNSS in-band authenticated position determination

Abstract: The present invention provides a system and method for determining the authenticity of reported positions of GNSS receivers, such as aircraft equipped with GPS positioning devices, and provides an in-band verification capability for GNSS positions by tasking one or more GNSS satellites as designated authentication support (DAS) satellites that transmit corrupted ephemeris data in a pseudo-random error corrupted C/A signal on the L1 band, and the GNSS receivers determine authentication ranges to the DAS satellites and transmit the DAS authentication ranges as part of their position report. The surveillance system can verify the authenticity by comparing the transmitted authentication ranges to true authentication ranges determined using actual ephemeris data and the known C/A code pseudo-random error for the DAS satellites.

Optimized Selection of Satellite Subsets for a Multi-Constellation GBAS

Abstract: In the next generation of Ground Based Augmentation System (GBAS) corrections and integrity parameters for two frequencies and multiple constellations will be provided. However, the capacity of the VDB (VHF Data Broadcast) link providing those parameters to users is strongly limited. Thus providing all those new corrections and parameters would either require a longer update rate of corrections or a limitation on the number of satellites to which corrections are provided. In this paper we propose a new satellite selection method which allows fast selection of a variable sized, quasi-optimal subset of all visible GNSS satellites. The proposed selection heuristic bases on a strong correlation between the third (i.e. vertical) component inside the S-matrix for each satellite and the probability of the related satellite being part of a subset which provides a favorable vertical protection level. Utilizing this correlation we design an algorithm which converges fast and leads to optimal results for a majority of constellations. As the selection can be performed for an arbitrary number of satellites and the complexity is not exponentially scaling with the number of available satellites, as an exhaustive search (brute-force) does, the heuristic is flexible and suitable for different applications even beyond GBAS’s. In the context of GBAS these subsets still provide reliable protection levels as the contribution to the accuracy is dropping with every additional satellite. We show the feasibility of using for instance only 14 satellites in global protection level simulations. In a multi-frequency multi-constellation GBAS architecture the approach of selecting only an optimal subset allows to keep the current 2 Hz update rate. This could mitigate problems with VDB capacity or remove the necessity of additional, more frequent integrity messages.

Prototyping a GNSS-Based Passive Radar for UAVs: An Instrument to Classify the Water Content Feature of Lands.

Abstract: Global Navigation Satellite Systems (GNSS) broadcast signals for positioning and navigation, which can be also employed for remote sensing applications. Indeed, the satellites of any GNSS can be seen as synchronized sources of electromagnetic radiation, and specific processing of the signals reflected back from the ground can be used to estimate the geophysical properties of the Earth’s surface. Several experiments have successfully demonstrated GNSS-reflectometry (GNSS-R), whereas new applications are continuously emerging and are presently under development, either from static or dynamic platforms. GNSS-R can be implemented at a low cost, primarily if small devices are mounted on-board unmanned aerial vehicles (UAVs), which today can be equipped with several types of sensors for environmental monitoring. So far, many instruments for GNSS-R have followed the GNSS bistatic radar architecture and consisted of custom GNSS receivers, often requiring a personal computer and bulky systems to store large amounts of data. This paper presents the development of a GNSS-based sensor for UAVs and small manned aircraft, used to classify lands according to their soil water content. The paper provides details on the design of the major hardware and software components, as well as the description of the results obtained through field tests.

Comparison Between Ratio Detection and Threshold Comparison for GNSS Acquisition

Abstract: A comparison between two widespread global navigation satellite system (GNSS) acquisition strategies is presented. The first strategy bases its decision on comparing the energy within a cell to a threshold, while the second one uses the ratio between the two largest cell energies. It is shown that the first method outperforms the second one in terms of receiver operating characteristics (ROCs) in many practically relevant cases. Moreover, despite the purported simplicity of the ratio detection method, it is further shown that its complexity is comparable to or even higher than the one of threshold comparison with adaptive threshold setting.