O desenvolvimento técnico da eletrônica, a contínua redução do tamanho dos receptores GNSS, associada à diminuição do consumo de energia, transformaram estes produtos em alguns circuitos integrados ou apenas pequenos chips do tamanho de um botão de uma camisa. Desta forma pode-se promover a sua integração com inúmeros dispositivos eletrônicos. A associação com os telefones celulares foi principalmente impulsionada pelo mandato de aprimoramento dos serviços 911 (E911) da Federal Communications Commission (FCC) nos Estados Unidos, exigindo que todas as operadoras de telefonia móvel daquele país fornecessem a localização com boa precisão das chamadas de emergência. Esta necessidade estimulou a produção dos chips em larga escala e, portanto, a diminuição do custo e a sua popularização. Desta maneira quase que em sua totalidade, os telefones celulares são hoje fabricados com receptores GPS, o que torna estes dispositivos uma das fontes mais baratas de se obter o Geoposicionamento. Acontece que existe uma lacuna na literatura quanto à precisão e a exatidão das coordenadas fornecidas por estes equipamentos. O presente trabalho visa, através de testes estatísticos e da comparação com outros receptores GPS e métodos, quantificar estes valores e propor uma metodologia para melhorar tal posicionamento. Para conseguir o objetivo, a estrutura do Sistema Operacional do telefone foi modificada de tal modo que fosse possível o acesso às observáveis do chipset do GPS embarcado e convertidos para o padrão RINEX de arquivamento de dados brutos. Os testes foram executados com o equipamento original e com o equipamento modificado com a instalação de uma antena externa e mostraram que com a utilização da medida de fase da portadora o equipamento pode fornecer o posicionamento com uma precisão média de 0,069m, com o desvio padrão de 0,047m e erro planimétrico de posicionamento máximo de 0,218m e mínimo de 0,004m. / The technical development of electronics, the continuous reduction in the size of GNSS receptors, allied with the energy consumption decrease, transformed these products into some integrated circuits or in small Chips as small as size of a button of a shirt. In this way one can promote its integration with countless electronic devices. The association with cell phones was mainly driven by the mandate to enhance services 911 (E911) of the Federal Communications Commission (FCC) in the United States, requiring that all mobile carriers of that country provide all the emergency calls location with good accuracy. So as to fulfill this necessity, the production of Chips in a large scale has been stimulated and therefore the decrease in cost and its popularity. In this way almost in its entirety, cell phones are now manufactured with GPS receivers, which makes these devices one of the cheapest sources to obtain the geopositioning. It turns out that there is a gap in the literature about how precise and accurate the coordinates provided by these equipments can be. This thesis aims through statistical tests and comparison with other GPS receivers and methods, quantify these values and propose a methodology to improve such positioning. To achieve the objective, the structure of the phone\'s operating system was modified in such a way that it was possible to access the embedded GPS Chipset observables and then converted into the RINEX standard raw data file. The tests were carried out with the original equipment and with the modified ones, with an external antenna installation which showed that using the phase measure of the carrier, the equipment can provide a positioning with an average accuracy of 0, 069m, with a default deviation of 0, 047m and a maximum planimetric positioning error of 0, 218m and a minimum of 0, 004m.

Lake Vostok, der größte der über 70 subglazialen Seen in der Antarktis, ist derzeit einer der Forschungsschwerpunkte der geowissenschaftlichen Polarforschung. Der See erstreckt sich unter einer 4 000 m dicken Eisschicht auf über 250 km Länge mit einer Wassertiefe von bis zu 1 000 m. Ziel der hier vorliegenden Arbeit ist die Untersuchung des Einflusses der Gezeiten auf den Wasserstand des Sees, die eine bisher nicht betrachtete Komponente in der Zirkulation im See darstellen. Auf Grund seiner Ausdehnung ist das Gezeitenpotential an verschiedenen Punkten auf dem See nicht gleich, sondern weist differentielle Unterschiede auf. Unter der Annahme, dass sich die Seeoberfläche entlang einer Äquipotentialfläche ausrichtet, ergeben sich Gleichgewichtsgezeiten des Sees mit Amplituden von bis zu 4,6 mm für die größte ganztägige Tide K1 und 1,8 mm für die größte halbtägige Tide M2. Differenzen des Luftdruckes zwischen Nord- und Südteil des Sees rufen zusätzlich einen differentiellen inversen Barometer-Effekt hervor. Der inverse Barometer-Effekt besitzt im wesentlichen die spektralen Eigenschaften eines roten Rauschens. Die Variationen erreichen bis zu +/- 20 mm. Zum messtechnischen Nachweis derartiger Höhenänderungen an der Eisoberfläche über dem See wurden drei unterschiedliche Verfahren herangezogen. Differentielle GPS-Messungen zwischen einem Punkt auf aufliegendem Eis und einem zweiten in der südlichen Seemitte bestätigen die Modellvorstellungen und zeigen sowohl mit der Luftdruckdifferenz korrelierte Höhenänderungen als auch Höhenänderungen mit ganz- und halbtägigen Perioden. Die SAR-Interferometrie als flächenhaft arbeitende Methode zur Bestimmung von Höhenänderungen lässt den räumlichen Verlauf der Deformation erkennen. Dabei zeigt sich, dass sich die Aufsetzzone auf dem etwa 50 km breiten See bis in die Seemitte ersteckt. Erdgezeitenregistrierungen, die im Jahr 1969 in der Station Vostok durchgeführt wurden, zeigen zwar Auffälligkeiten wie etwa einen stark erhöhten Luftdruckregressionskoeffzienten und einen Phasenvorlauf der K1-Tide, diese können jedoch nicht eindeutig als Resultat von Höhenänderungen der Seeoberfläche identifiziert werden. Auf Grund der Lage der Station Vostok nahe dem Ufer des Sees ist die Deformation dort schon stark gedämpft. Die zu erwartenden Effekte liegen daher unterhalb der Auflösung der damaligen Messungen. Damit sind die theoretischen Grundvorstellungen über die Reaktion des subglazialen Sees auf Gezeiten- und Luftdruckanregungen herausgearbeitet, sowie diese Effekte mit zwei unabhängigen und komplementären Messverfahren nachgewiesen. / Lake Vostok, the largest of more than 70 subglacial lakes in the Antarctic, is one of the prominent topics of recent geoscientific polar research. The lake extends beneath the 4,000 m thick ice sheet to a length of more than 250 km with a water depth of up to 1,000 m. This thesis aims to investigate the influence of tides on the lake level which has not been considered so far in the discussion of water circulation within the lake. Due to the extent of the lake the tidal potential at different positions on its surface is not equal but exhibits a differential effect. Under the assumption of the lake level to be parallel to an equipotential surface the equilibrium tides of the lake yield amplitudes of up to 4.6 mm for the largest diurnal tidal constituent K1 and 1.8 mm for the largest semi-diurnal wave M2. In addition, differences in air pressure between the northern and the southern part of the lake result in a differential inverse barometric effect. This effect shows red noise characteristics with variations of up to +/- 20 mm. Three different types of measurements were used to verify corresponding height changes of the ice surface above the lake. Differential GPS measurements between one station on grounded ice and one in the southern centre of the lake confirm the concept and show height changes correlated to air pressure differences as well as changes with diurnal and semi-diurnal periods. SAR interferometry as a spatial method to determine height changes reveals the areal extent of the deformation with a grounding zone extending to the centre of the about 50 km wide lake. Gravimetric earth tide data recorded at Vostok Station in 1969 show pecularities such as an increased regression with air pressure and a phase lead of the K1 tide. However, these effects cannot be explicitly attributed to height changes of the lake surface. Due to the position of the station near the edge of the lake the effect is highly attenuated and below the noise level of these measurements. This work introduces the concept of the response of the subglacial lake to the tidal potential and to air pressure forcings and presents evidence for the effect by two different techniques proving the validity of the model.

The aim of my dissertation work was to create an application for pocket PC with operating system Windows Mobile and touch screen, an application that would enable to position the current location of the pocket PC based on the GPS data, on distance measurement between two and more points of which the location is obtained from GPS, and on measurement of territory surface defined by certain number of points obtained from the GPS. The application also enables to display the characteristics of the received GPS signal, information about the number of visible satellites and also information about maximum deviation from positioning. In order to increase the accuracy of the positioning, an averaging function has been implemented. As additional function, a possibility of route location has been created. It measures the passed distance and records some other route characteristics. The application has been successfully tested on pocket PC E-ten M600+ and GPS receiver Navilock but it has been designed with general-purpose and should be compatible with all devices working with operating system Windows Mobile and touch screen. The text section of my dissertation work describes the positioning principle on the basis of satellites with known position, deals with the accuracy of these systems and describes few possibilities how to increase their accuracy. It also discusses the NMEA 0183 Protocol that is used by the majority of GPS modules for communication. The text section also describes several mathematic and cartographic calculations needed for realization of the application. In the end of the text section there is a detailed description of the created application.

Diploma thesis deals with the possibilities of using GPS when analysing road accidents. The history and structure of U.S. global positioning system, Russian GLONASS system and European Galileo system are described. GPS receivers are sorted out by the possibility of use. The thesis deals with the methods of refinement GPS and how the vehicles can be monitored using GPS. In the practical part of this diploma thesis measurements with several types of navigations were made. And a comparison of accuracy of measured data with the real situation where the car was found at the moment of measuring followed and how fast was gone.

Advance Driver Assistance System (ADAS) are becoming the main issue in today’s automotive industry. The new generation of ADAS aims at focusing on more details and obtaining more accuracy. To achieve this objective, the research and development parts of the automobile industry intend to utilize Global Positioning System (GPS) by integrating it with other existing tools in ADAS. There are several driving assistance systems which are served by a digital map as a primary or a secondary sensor. The traditional techniques of digital map generation are expensive and time consuming and require extensive manual effort. Therefore, having frequently updated maps is an issue. Furthermore, the existing commercial digital maps are not highly accurate. This Master thesis presents several algorithms for automatically converting raw Universal Serial Bus (USB)-GPS and Real Time Kinematic (RTK) GPS traces into a routable road network. The traces are gathered by driving 20 times on a highway. This work begins by pruning raw GPS traces using four different algorithms. The first step tries to minimize the number of outliers. After the traces are smoothed, they tend to consolidate into smooth paths. So in order to merge all 20 trips together and estimate the road network a Trace Merging algorithm is applied. Finally, a Non-Uniform Rational B-Spline (NURBS) curve is implemented as an approximation curve to smooth the road shape and decrease the effect of noisy data further. Since the RTK-GPS receiver provides highly accurate data, the curve resulted from its GPS data is the most sufficient road shape. Therefore, it is used as a ground truth to compare the result of each pruning algorithm based on data from USB-GPS. Lastly, the results of this work are demonstrated and a quality evaluation is done for all methods.

No description available.

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / The embedded system related hardware technology has experienced rapid development, and it provided the software technology with a huge space for growth. Therefore using software approaches to perform GPS receiver functions in a powerful and generic hardware platform is becoming more feasible. In this paper, the software GPS receiver technology and the design basics of the software receiver are discussed. Further in the Matlab simulation environment, the implementation of a software receiver for replacing the processing functions of ASIC in traditional GPS receivers, i.e. RF front end and multi-channel correlator, is presented. Some simulation results and implementation details are included.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Vehicle Monitoring System (VMS) has being introduced into the world marketplace with the hope that it will help alleviate traffic congestion and the associated environmental pollution. In this paper we give an overview of system composition and principle of the VMS and several communications link solutions in China. We review technologies and focus on the key technological issues about the integration of VMS with the GPRS wireless mobile network and the Internet.

ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, California / For the final evaluation of a GPS attitude determination algorithm, it was determined its true performance in terms of accuracy, reliability and dynamic response. To accomplish that, a flight test campaign was carried out to validate the attitude determination algorithm. In this phase, the measured aircraft attitude was compared to a reference attitude, to allow the determination of the errors. The system was built using non-dedicated airborne GPS receivers, and a complete Flight Tests Instrumentation (FTI) System. The flight test campaign was carried out at the Brazilian’s Flight Test Group T-25C 1956 Basic Trainer aircraft. The performance and accuracy of the system is demonstrated under static and dynamics tests profiles, which are fully compliant with the Federal Aviation Administration (FAA) Advisory Circular (AC) 25-7A. Dynamic response of the system is evaluated.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Quartz crystal is an important electronic element in the field of communication systems, computer systems, etc. It is important to precisely measure the frequency of quartz crystal unit for manufacturing. The Pi-network transmission system recommended by International Electrotechnical Commission (IEC) is generally acknowledged as a measurement technique. However it needs a precise frequency source. The frequency source must be calibrated within a regular period in the process of manufacturing. Frequency counters, time internal counters, phase comparisons, which are the most common frequency calibrations, are introduced in the paper. Nowadays GPS has also become the primary system for frequency calibration. GPS receivers provide 1 PPS (Pulse Per Second) with accuracy < 100 nanoseconds to UTC under normal conditions. Motorola UT Oncore timing GPS with time accuracy < 50ns (1 sigma) uses time RAIM algorithm to ensure the validity and reliability of measurements. The comparison between the precise 1PPS and local reference is implemented. And the phase differences are logged and read by computer. According to the values, the frequency output of DDS is coordinated. In order to reduce the phase ambiguity, local reference is divided before comparison. The calibration can be implemented at any time by GPS. Block diagrams of calibration are presented in this paper.