Time filter

Source Type


Capua R.,SOGEI | Bottaro A.,SOGEI
24th International Technical Meeting of the Satellite Division of the Institute of Navigation 2011, ION GNSS 2011 | Year: 2011

The paper presents the work of the Sogei GNSS R&D Group for the development of a GNSS SDR receiver for institutional applications. Target applications are high accuracy GNSS Surveying for Land Registry, Customs Border Control and Tracing and Tracking. The objective of the project is to build a Real-Time GNSS SDR receiver running on a Notebook, based on COTS and internal developed source code. The GNSS SDR receiver is composed by an RF Front-End and four software modules: Data Dispatcher, Acquisition, Tracking and PVT. The Software has been written in C++, using SIMD primitives. Communication is performed through TCP/IP sockets. Look-Up tables are used for Code and Carrier replicas and logic operations. The RF Front-End was developed using a reconfigurable commercial IC sampler and is connected to the Notebook through USB. IF is 1.023 MHz and undersampling is performed at 4.092 MHz. A Data Dispatcher spools samples to the processing modules. The Parallel Search Acquisition provides results in about 300 ms for 32 GPS and 4 SBAS channels, using FFT and zero-padding. Code matching ambiguities are avoided. Tracking loop works on bit-parallelized samples through a second order PLL and a first order FLL. Correlation is performed using logical tables, while a Dot product DLL discriminator is used. The Tracking processes Is of samples in less than 50 ms per channel. PVT is implemented through an Extended Kaiman Filter and outputs NMEA. A DSP GNSS SDR, developed for achieving high performance processing, provides results comparable to the PC platform. At the end of the First Phase of the Project, the GNSS SDR receiver implements Real-Time GPS, GIOVE-A/B and SBAS Acquisition and Tracking, with an accuracy of 5 m. The Second Phase will implement a Multi-Carrier/Multi-Constellation Code/Phase SDR receiver based on Multi-Core programming, including Hybridization with external sensors and indoor positioning capabilities. Source

Capua R.,SOGEI | Bottaro A.,SOGEI
25th International Technical Meeting of the Satellite Division of the Institute of Navigation 2012, ION GNSS 2012 | Year: 2012

The paper presents the results of the development of advanced PVT solutions for the Sogei's GNSS SDR. Such Real-Time platform is based on an internally designed Front-End and is totally running on a General Purpose Notebook. The EKF deals with non-linear systems through process and observations functions linearization. Non-linearity errors can lead to poor Kalman filter performances or to divergence. Linearization does not allow correct state and measurements Covariance matrices propagation in presence of significant dynamic conditions. Jacobians introduce severe computational burdens and cannot be applied in the presence of discontinuities and singularities. In order to overcome such limitations, an Unscented Kalman Filter (UKF) algorithm has been developed and tested within the SDR. The UKF avoids linearization. Non-linear transformation is performed at each step on a set of deterministic sigma points extracted from the Covariance matrix, allowing prediction errors minimization. Dependence on initial conditions is reduced. Due to inherently quantized measurements and computational load constraints, SDR can highly benefit from the use of an UKF. In our implementation, a numeric efficient GPS L1 pseudoranges and Doppler measurements representation has been developed. A fine tuning phase has been carried out in mixed static and dynamic conditions. A test campaign has been carried out on a car equipped with the GNSS SDR. True trajectory was determined through RTK. An accuracy of 5m and improved robustness in case of abruptly changing routes is achieved. For SDR, a simple and inexpensive augmentation technique for medium level accuracy is advisable. A Local Augmentation based on Coordinates Corrections method has been implemented. Corrections are calculated at SDR rover side, using Reference Station measurements acquired through NTRIP and RTCM messages. An accuracy of 2 m is reached. Such a solution can pave the way for implementing reliable and low cost Augmentation systems totally based on SDR receivers. Source

Antonioli N.,SOGEI | Castano F.,Dip. del Tesoro | Coletta S.,SOGEI | Grossi S.,SOGEI | And 5 more authors.
Frontiers in Artificial Intelligence and Applications | Year: 2014

In this paper we present an ontology-based data management (OBDM) project concerning the Italian public debt domain, carried out within a joint collaboration between Sapienza University of Rome and the Department of Treasury of the Italian Ministry of Economy and Finance. We discuss the motivations at the basis of this project and present the main characteristics of the ontology we have built. We also describe the mechanisms we used to link the ontology to the actual data and the tools we have adopted for supporting ontology development and maintenance, as well as exploiting OBDM services. Finally, we provide a thorough evaluation of the ontology we produced and discuss in detail the role that it plays within the whole information system of the ministry department responsible for managing Italian public debt data. © 2014 The authors and IOS Press. All rights reserved. Source

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