This thesis evaluates a hypothesis about how to implement a low cost Differential GPS (DGPS) solution, able to find a current location with a precision almost as good as more expensive DGPS solution.  For this purpose two Smartphone’s are used, one used as a fixed reference station and another used as a roving receiver. The reference station calculates the temporary error at its location at every second and transmits these errors to a server over the internet.  The roving receiver requests to the server to get the latest error from the reference station over the internet. By using these errors or differences, the roving receiver finds a corrected location. The results are in the same range as dedicated DGPS solutions.

No description available.

International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / The Talking GPS Locating System (TGLS) was developed to facilitate recovery of airborne targets by vocalizing and transmitting their Global Positioning System (GPS) coordinates to surface recovery teams following target splashdown. The airborne portion of the TGLS includes an off-the-shelf five-channel GPS receiver board, a GPS antenna, a microcontroller board with voice sample/playback circuitry, and a transmitter with antenna. Also part of the TGLS is a Record/Test Unit (RTU) which is used for pre-launch voice recording and ground tests. Upon splashdown, the TGLS is energized, the GPS receiver is initialized, and an optional homing tone burst -- periodically interrupted by a voice message relaying target and GPS receiver status -- is transmitted. Once the receiver has output valid longitude and latitude information to the microcontroller, this position is vocalized as the GPS status portion of the broadcast message. Just one intelligible reception of this message by any inexpensive, properly-tuned voice receiver will allow recovery teams to vector to within 25 to 100 meters of the target regardless of weather conditions or the time of day.

International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, California / GPS is required in today's vehicle tracking and navigation applications. The Navigation Satellite Timing and Ranging (NAVSTAR GPS) is an all-weather. Radio based, satellite navigation system that enables users to accurately determine 3-dimensional position, velocity and time. So it is an intelligent sensor intended to be used as a component in a system for public service.

International Telemetering Conference Proceedings / October 26-29, 1992 / Town and Country Hotel and Convention Center, San Diego, California / The Air Force Flight Test Center (AFFTC) at Edwards, California has installed the Edwards Digital Switch (EDS). The EDS is a DS-1 switch capable of switching voice, encrypted voice, and Time Space Position Information (TSPI) data. Communicating encrypted voice and TSPI data reliably from the EDS to any other communication system requires the two systems operate using the same frequency reference. The need to communicate with other test ranges and over commercially leased lines using the EDS requires synchronization to a standard frequency source. The current synchronization method used at the AFFTC is unacceptable for the EDS. A hierarchal system of synchronization networking will be implemented to provide a common reference to each of the systems interfacing the EDS. The Master Timing Station (MTS), which provides synchronization reference to most of the AFFTC resources, is aging and must be upgraded. The upgrade of the MTS and the restructuring of the synchronization signal distribution will be completed simultaneously. Traceability to the United States Naval Observatory (USNO) and the National Bureau of Standards (NBS) is required to provide the necessary synchronization to allow the EDS to interface reliably with other systems. The Global Positioning System (GPS) is being considered as the primary source for frequency calibration traceable to the USNO and NBS.

International Telemetering Conference Proceedings / October 26-29, 1992 / Town and Country Hotel and Convention Center, San Diego, California / The ionosphere is a critical link in the earth's environment for space-based navigation, communications and surveillance systems. Signals sent down by the GPS satellites can provide an excellent means of studying the complex physical and chemical processes that take place there. GPS uses two frequencies to ascertain signal delays passing through the ionosphere. These are measured as errors and used to correct position solutions. Since this process is a means of measuring columns of Total Electron Content (TEC), multiple top-soundings from the GPS constellation could provide significant detail of the ionospheric pattern and possibly lead to enhancement of predictions for selectable areas and sites. This paper addresses transforming the GPS propagation delays (errors) into TEC and providing TEC contours on a PC-style workstation in real and integrated time and discusses a worldwide ionospheric network monitoring system.

This work presents two approaches for integrating data from a low cost GPS receiver in a Monte Carlo localization algorithm. Firstly, an easily applicable method based on data in the standard NMEA protocol is shown. Secondly, an original algorithm utilizing lower level pseudorange measurements accessed in binary receiver-specific format is presented. In addition, a set of tools for analysis of GPS measurement errors on receivers with SiRF III chipset was implemented

Single-frequency Global Positioning System (GPS) receivers do not accurately compensate for the ionospheric delays imposed upon GPS signals. This can lead to significant errors and single-frequency systems rely upon models to compensate. This investigation applies 4D (four-dimensional) ionospheric tomography to GPS timing for the first time. The tomographic algorithm, MIDAS (Multi-Instrument Data Analysis System), is used to correct for the ionospheric delay and the results are compared to existing single and dual-frequency techniques. Days during the solar maximum years 2002, 2003 and 2004 have been chosen to display results when the ionospheric delays are large and variable. Maps of the ionospheric electron density, across Europe, are produced by using data collected from a fixed network of dual-frequency GPS receivers. Results that improve upon the use of existing ionospheric models are achieved for fixed (static) and mobile (moving) GPS receiver scenarios. The effects of excluding all of the GPS satellites below various elevation masks, ranging from 5° to 40°, on timing solutions for fixed and mobile situations are also presented. The greatest timing accuracies when using the fixed GPS receiver technique are obtained by using the highest mask. The mobile GPS timing solutions are most accurate when satellites at lower elevations continue to be included. Furthermore, timing comparisons are made across baselines up to ~4000 km and the ionospheric errors are shown to increase with increasing baseline. GPS time transfer is then investigated and MIDAS is shown to improve the time transfer stabilities of a single-frequency GPS system. The results are comparable to the dual-frequency time transfer after ~2 hours averaging time. Overall, the MIDAS technique provides the most accurate and most stable results (comparable to dual-frequency) for a single-frequency based GPS system. Ionospheric corrections (via MIDAS) may be broadcast to users nationally or via the internet for example, opening up the possibility of improving the accuracy and stability of single-frequency GPS systems in real-time.

This research demonstrates the potential of novel technology for space-based remote sensing of the topside ionosphere-plasmasphere, supported by ionospheric imaging, which can augment and enhance our current understanding of the Earth’s plasmasphere. The research was conducted in two phases. The first was the development of a technology demonstrator ‘TOPCAT’ that installed a dual-frequency GPS receiver dedicated for topside ionosphere-plasmasphere imaging into a Low Earth Orbit (LEO). The novelties of TOPCAT were that it was designed from commercial-off-the-shelf (COTS) components and was installed on-board the CubeSat ‘UKube-1’, greatly reducing development and launch costs of the instrument. The successful launch of TOPCAT for space-borne remote sensing of the topside ionosphere and plasmasphere could provide the necessary proof of concept for the installation of a constellation of CubeSats – a possible next phase that may be implemented in the future. Thus, in its first stage, the thesis discusses the development of TOPCAT, together with design challenges encountered from constraints imposed by CubeSat technology. The discussion also includes the series of qualification tests performed to successfully qualify TOPCAT as a space-worthy payload design that can remotely image regions beyond the ionosphere. The second phase of research was the validation of the Multi-Instrument Data Analysis System (MIDAS) for the topside ionosphere and plasmasphere. A tomography algorithm originally developed for the ionosphere, MIDAS uses total electron content (TEC) measurements from differential phase of GPS signals, and inverts them to derive the electron density of the region. The thesis investigates the extension of MIDAS to image regions beyond the ionosphere by validating the algorithm for the topside ionosphere and plasmasphere. The process was carried out by first reconstructing a simulation by Gallagher et al. [1988] to verify the quality of the images. This was followed by the use of real GPS phase data from the COSMIC constellation to reconstruct the topside ionosphere-plasmasphere, and the qualitative comparison of the images with previous independent observations obtained through COSMIC and Jason-1 missions. Results showed that MIDAS can successfully reconstruct the undisturbed (quiet) topside ionosphere-plasmasphere using COSMIC data. However, imaging the storm-time topside ionosphere-plasmasphere requires better data coverage (i.e. more receivers) as the resolution offered by COSMIC was not sufficient to reconstruct fast-evolving structures – thereby emphasising the need for more data sources providing high resolution global coverage, such as a constellation of CubeSats with LEO-based GPS receivers.

Este trabalho trata da proposta de um Sistema de Gestão da Qualidade para uma empresa genérica prestadora de serviços de posicionamento com o GPS, como alternativa para melhorar a gestão da organização e garantir a qualidade de seus serviços e produtos. O aumento da demanda por esse tipo de serviço estimulou o aparecimento de novas empresas específicas em GPS e adaptação de antigas para atender um mercado crescente e cada vez mais exigente. Por se tratar de um processo novo, sua implantação requer mudanças significativas tanto de ordem técnica (intimamente ligadas ao conhecimento específico do sistema e suas capacidades) como administrativa (meios e políticas que possam garantir uma gestão efetiva de todos os processos envolvidos no posicionamento com o GPS dentro da empresa). A modernização imposta ao setor de topografia e geodésia em seu cenário produtivo e econômico, com o aparecimento de novas técnicas produtivas e ferramentas gerenciais, não pode mais ser protelada. Isso impõe às organizações uma necessidade emergencial de mudança e grandes desafios, entre eles o de sua própria sobrevivência. A execução de um serviço de posicionamento com o sistema GPS consiste em uma seqüência de procedimentos práticos que, se forem bem executados, proporcionarão maior probabilidade de êxito ao resultado final. Os procedimentos dependem muito de cada caso, e normalmente são definidos por indicações dos fabricantes dos instrumentos, normas e especificações oficiais e, na grande maioria das vezes, pela própria experiência prática do responsável. Como parte desse trabalho foi desenvolvida uma pesquisa social para identificar como são e como agem as empresas que prestam serviços de posicionamento com o sistema GPS no Brasil. Com base nos resultados dessa pesquisa, elaborou-se uma empresa genérica de posicionamento com GPS, com características similares à maioria, e que serviu como referência na concepção dos padrões para os processos básicos da empresa. O modelo de gestão da qualidade proposto teve como guia o Sistema da Qualidade preconizado pela ISO série 9000. Consideraram-se também as ferramentas de gestão e controle da qualidade comumente aplicados na indústria de manufatura e adaptados aos serviços de um posicionamento com GPS. O resultado apresenta uma seqüência de implantação do modelo com as devidas recomendações e viabilidades. Para ilustrar, são apresentados os resultados benéficos obtidos com a aplicação direta dos padrões técnicos da empresa genérica, em um posicionamento real para pontos estáticos, em que se considerou apenas a parte produtiva. O resultado mostrou-se bastante convincente. / This thesis deals with a proposal for quality management for a generic GPS surveying company as an alternative to management and service quality improvement. As a result of the GPS measurement demand increasing, an important number of new companies and/or renovated ones have been established in order to operate in that market. But considering that it is a new process some changes must be performed in order to accommodate the old surveying techniques and the old fashioned management to the new reality. This implies in a new management organization which must be based on a well described procedure sequence aiming a final quality control success. As an important part of that research a social research has been applied to several Brazilian GPS service provider companies with the purpose of knowing the status of the sector related to the quality management. Based on that research a hypothetical company was considered in order to give subsides to the elaboration of a standardized company. The proposed quality management model was based on the ISO 9000 Quality System adopting management tools and quality control operators applied in the general industry adapted to the GPS surveying companies. This thesis shows the results of that research presenting an implementation model for quality management considering a real surveying GPS work based on the new GPS measurement techniques.