Implementation of Moving-Base-GNSS en NAVKA Multisensor GNSS / MEMS /optics navigation algorithms and systems

[EN] Implementation of Moving-Base-GNSS in NAVKA Multisensor GNSS / MEMS / Optics Navigation Algorithms and Systems. Development and implementation of an ambiguity resolution algorithm related to the Moving-Base-GNSS situation. Algorithm implementation in the RTKLIB open source library (C / C ++). Development of software that allows to calculate the position of a rover from the coordinates of a master receiver (DGNSS / PPP) and from the baselines calculated with the algorithm in question.[ES] Implementation of Moving-Base-GNSS in NAVKA Multisensor GNSS/MEMS/Optics Navigation Algorithms and Systems. Desarrollo e implementación de un algoritmo de resolución de ambigüedades relacionado con la situación Moving-Base-GNSS. Implementación del algoritmo en la librería de código abierto RTKLIB (C/C++). Desarrollo de un software que permite calcular la posición de un rover a partir de las coordenadas de un receptor máster (DGNSS/PPP) y de las líneas base calculadas con el algoritmo en cuestión.Hernández Olcina, J. (2019). Implementation of Moving-Base-GNSS en NAVKA Multisensor GNSS / MEMS /optics navigation algorithms and systems. http://hdl.handle.net/10251/139434TFG

Adaptive restoration of text images containing touching and broken characters

For document processing systems, automated data entry is generally performed by optical character recognition (OCR) systems. To make these systems practical, reliable OCR systems are essential. However, distortions in document images cause character recognition errors, thereby, reducing the accuracy of OCR systems. In document images, most OCR errors are caused by broken and touching characters. This thesis presents an adaptive system to restore text images distorted by touching and broken characters. The adaptive system uses the distorted text image and the output from an OCR system to generate the training character image. Using the training image and the distorted image, the system trains an adaptive restoration filter and then uses the trained filter to restore the distorted text image. To demonstrate the performance of this technique, it was applied to several distorted images containing touching or broken characters. The results show that this technique can improve both pixel and OCR accuracy of distorted text images containing touching or broken characters

Polarized-interferometer feasibility study

The feasibility of using a polarized-interferometer system as a rendezvous and docking sensor for two cooperating spacecraft was studied. The polarized interferometer is a radio frequency system for long range, real time determination of relative position and attitude. Range is determined by round trip signal timing. Direction is determined by radio interferometry. Relative roll is determined from signal polarization. Each spacecraft is equipped with a transponder and an antenna array. The antenna arrays consist of four crossed dipoles that can transmit or receive either circularly or linearly polarized signals. The active spacecraft is equipped with a sophisticated transponder and makes all measurements. The transponder on the passive spacecraft is a relatively simple repeater. An initialization algorithm is developed to estimate position and attitude without any a priori information. A tracking algorithm based upon minimum variance linear estimators is also developed. Techniques to simplify the transponder on the passive spacecraft are investigated and a suitable configuration is determined. A multiple carrier CW signal format is selected. The dependence of range accuracy and ambiguity resolution error probability are derived and used to design a candidate system. The validity of the design and the feasibility of the polarized interferometer concept are verified by simulation

Reverse Engineering Low-Level Design Patterns From Object-Oriented Code.

The purpose of this research is to develop and automatically extract an abstract representation model of object-oriented (abbreviated as OO) software systems that captures the structure of the system and code dependencies, in order to aid maintenance. The research resulted in the development of two abstract representation models--the low-level design pattern (LLDP) abstract model and the low-level software architecture (LLSA) abstract model. The LLDP model is at a higher level of abstraction than the LLSA model. The LLSA model acts as an intermediate representation between the LLDP model and an OO software system. The design of the LLSA and LLDP representation models and the automatic extraction of these models from an OO software system are significant contributions of this research. An LLDP representation is a textual description of common OO strategies. Three sets of LLDPs--polymorphism, decoupling and messages are defined. LLDPs describe the structure, the benefits and consequences of a strategy. The design of the LLSA model considers the complexities inherent in OO systems, and the requirements of a maintainer from such a model. The LLSA model defines software components, static and dynamic interfaces of components and static and dynamic interactions between components. Software components are defined in terms of OO programming language constructs and interactions between the components are defined in terms of OO relationships that exist between the components. Understanding the relationships is necessary to understand what dependencies occur and why they occur in the code. The LLSA abstract model in conjunction with the LLDPs provides a view of software systems that captures the dependency relationships between code, the nature of the dependencies and the reasons why the dependencies must exist and be preserved. The LLSA model of C++ software systems in particular are defined. The usefulness of LLSA and LLDPs from the maintenance perspective are explored. A prototype CASE tool, pulse was implemented to demonstrate the feasibility of automatic extraction of both models. Reverse engineering and code analysis techniques were developed to extract the LLSA relationships and interfaces and to recognize LLDPs

Synchronization in digital communication systems: performance bounds and practical algorithms

Communication channels often transfer signals from different transmitters. To avoid interference the available frequency spectrum is divided into non-overlapping frequency bands (bandpass channels) and each transmitter is assigned to a different bandpass channel. The transmission of a signal over a bandpass channel requires a shift of its frequency-content to a frequency range that is compatible with the designated frequency band (modulation). At the receiver, the modulated signal is demodulated (frequency shifted back to the original frequency band) in order to recover the original signal. The modulation/demodulation process requires the presence of a locally generated sinusoidal signal at both the transmitter and the receiver. To enable a reliable information transfer, it is imperative that these two sinusoids are accurately synchronized. Recently, several powerful channel codes have been developed which enable reliable communication at a very low signal-to-noise ratio (SNR). A by-product of these developments is that synchronization must now be performed at a SNR that is lower than ever before. Of course, this imposes high requirements on the synchronizer design. This doctoral thesis investigates to what extent (performance bounds) and in what way (practical algorithms) the structure that the channel code enforces upon the transmitted signal can be exploited to improve the synchronization accuracy at low SNR