This study aims to compare advantages and disadvantages between detail surveying done with a drone (UAS) and GNSS equipment. Thus, in order to examine if detail surveying with UAS can be applicable for creating base maps in a more time efficient way. Aspects such as accuracy, environment, surroundings and ethics are shown consideration for. This was carried out by comparing data sampled from UAS flying and detailed surveying with GNSS. The flight altitude was 65 meters and the aerial photos were processed in Agisoft Metashape and ArcMap. GNSS was used to measure objects with high frequency, roughly 16 points per second and was later processed in GEO and ArcMap. Additional surveying was done with a total station in areas where the accuracy didn’t meet the requirements set by HMK. Establishment of free station was used when measuring with total station and the objects were then surveyed with a prism and direct measuring. Results that are relevant to this study are mainly RMS (Root Mean Square) and standard uncertainty. The results show that the time required for detailed surveying with UAS is 6 hours and 45 minutes, whilst for GNSS the time required is 8 hours and 30 minutes. Considering the RMS value and the standard uncertainty, the differences are marginally different. RMS value for UAS is 0.088 meters and standard uncertainty is 0.062 meters whilst for GNSS the RMS value is 0.084 meters and standard uncertainty is 0.058 meters. All measurements and results are within the 2nd standard level which are the requirements for a base map within an urban area. The results can be seen as reliable as the requirements set by HMK when practicing detailed surveying with UAS, GNSS and total station was followed. The time efficiency achieved when doing detailed surveying with UAS can make up for the increase in standard uncertainty as long as the results are within the recommendations set by HMK. Further studies could be applied to see how similar surveying results could look in areas with different environments and different sizes.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / An integrated design, Test and Evaluation (T&E) system for GPS receiver is proposed in the paper, which can perform T&E early in R&D cycle, and combine new designs into a conceptual GPS receiver directly. The flowchart of its development mode is given. The architectures of the system, especially of the signal-computing software are described with frame diagrams. The mathematical models of three reference points are derived, with the impact of oscillator errors modeled. Future plans and further developments are also discussed.

One challenge for Autonomous Underwater Vehicle (AUV) multibeam surveying is the limited ability to assess internal vertical agreement rapidly and reliably. Applying an external ellipsoid reference to AUV multibeam data would allow for field comparisons. A method is established to merge ellipsoid height (EH) data collected by a surface vessel in close proximity to the AUV. The method is demonstrated over multiple collection missions in two separate areas. Virtual tide corrector values are derived using EH data collected by a boat and a measured ellipsoid to chart datum separation distance. Those values are compared to measurements by a traditional tide gauge installed nearby. Results from the method had a mean difference of 6 centimeters with respect to conventional data and had a mean total propagated uncertainty of 15 centimeters at the 95% confidence interval. Methodologies are examined to characterize their accuracies and uncertainty contribution to overall vertical correction.

Les avancées récentes dans le domaine de navigation par satellites (GNSS) ontconduit à une prolifération des applications de géolocalisation dans les milieux urbains. Pourde tels environnements, les applications GNSS souffrent d’une grande dégradation liée à laréception des signaux satellitaires en lignes indirectes (NLOS) et en multitrajets (MP). Cetravail de thèse propose une méthodologie originale pour l’utilisation constructive des signauxdégradés MP/NLOS, en appliquant des techniques avancées de traitement du signal ou àl’aide d’une assistance d’un simulateur 3D de propagation des signaux GNSS. D’abord, nousavons établi le niveau maximal réalisable sur la précision de positionnement par un systèmeGNSS "Stand-Alone" en présence de conditions MP/NLOS, en étudiant les bornes inférieuressur l’estimation en présence des signaux MP/NLOS. Pour mieux améliorer ce niveau deprécision, nous avons proposé de compenser les erreurs NLOS en utilisant un simulateur 3D dessignaux GNSS afin de prédire les biais MP/NLOS et de les intégrer comme des observationsdans l’estimation de la position, soit par correction des mesures dégradées ou par sélectiond’une position parmi une grille de positions candidates. L’application des approches proposéesdans un environnement urbain profond montre une bonne amélioration des performances depositionnement dans ces conditions. / Recent trends in Global Navigation Satellite System (GNSS) applications inurban environments have led to a proliferation of studies in this field that seek to mitigatethe adverse effect of non-line-of-sight (NLOS). For such harsh urban settings, this dissertationproposes an original methodology for constructive use of degraded MP/NLOS signals, insteadof their elimination, by applying advanced signal processing techniques or by using additionalinformation from a 3D GNSS simulator. First, we studied different signal processing frameworks,namely robust estimation and regularized estimation, to tackle this GNSS problemwithout using an external information. Then, we have established the maximum achievablelevel (lower bounds) of GNSS Stand-Alone positioning accuracy in presence of MP/NLOSconditions. To better enhance this accuracy level, we have proposed to compensate for theMP/NLOS errors using a 3D GNSS signal propagation simulator to predict the biases andintegrate them as observations in the estimation method. This could be either by correctingdegraded measurements or by scoring an array of candidate positions. Besides, new metricson the maximum acceptable errors on MP/NLOS errors predictions, using GNSS simulations,have been established. Experiment results using real GNSS data in a deep urban environmentshow that using these additional information provides good positioning performance enhancement,despite the intensive computational load of 3D GNSS simulation.

A caracterização morfométrica e hipsométrica de bacias hidrográficas permite o melhor entendimento do seu funcionamento enquanto sistema, facilita a correlação com suas características e potencializa diversos estudos. O emprego de métodos quantitativos e qualitativos para caracterizar uma bacia hidrográfica possibilita uma maior compreensão da sua dinâmica e por isso o emprego de vários parâmetros é fundamental. Nessa tese é apresentada a análise morfométrica e hipsométrica e a determinação automática de hidrografia e knickpoints na bacia da Lagoa Mirim, uma bacia transfronteiriça, localizada na costa atlântica da América do Sul entre os paralelos 31°S e 34°30’S e entre os meridianos 52°W e 55°30’W, com 58407.78km2 de área, dos quais 47% estão em território brasileiro e 53% em território uruguaio. A análise e obtenção dos parâmetros e a determinação automática de hidrografia e knickpoints na bacia da Lagoa Mirim, foi realizada com técnicas de Geoprocessamento, utilizando as ferramentas de análise espacial e de manipulação de dados do programa ArcGis, versão 10.2.2. Foram utilizadas 15 imagens SRTM (Shuttle Radar Topographic Mission), com resolução espacial de 1 segundo de arco (1”), aproximadamente 30m, para gerar o Modelo Digital de Elevação (MDE) da área de estudo. Este modelo foi validado com levantamento cinemático GNSS (Sistemas Globais de Navegação por Satélite), pós-processado com o método de Posicionamento por Ponto Preciso (PPP). As análises morfométrica e hipsométrica e a determinação da hidrografia e knickpoints da Bacia da Lagoa Mirim foram realizadas a partir do MDE SRTM. A hidrografia foi obtida com o Model Builder e ferramentas hidrológicas do ArcGis. E os knickpoints foram determinados através do Knickpoint Finder, um script em linguagem Python integrado ao ArcTollBox do programa ArcGis. Os resultados demonstram que a utilização de dados SRTM em ambiente SIG (Sistemas de Informação Geográfica) permite a caracterização de bacias hidrográficas, sendo útil para gestão e gerenciamento dos recursos hídricos e para estudos ambientais, mostrando-se uma alternativa prática e viável ao minimizar custos e tempo na execução dos trabalhos. / The morphometric and hypsometric characterization of river basins allows a better understanding of its functioning as a system, facilitates the correlation with its characteristics, and potentiates several studies. The use of quantitative and qualitative methods to characterize a river basin allows a better understanding of its dynamics, therefore the use of several parameters is fundamental. This thesis presents the morphometric and hypsometric analysis and the automatic determination of hydrography and knickpoints in the Mirim Lagoon Basin. Mirim Lagoon basin is a transboundary basin, located in the Atlantic coast of South America, between parallels 31°S and 34°30’S and meridians 52°W and 55°30'W, with an area of 58,407.78 km2, being 47% in Brazilian territory and 53% in Uruguayan territory. The analysis and acquisition of morphometric and hypsometric parameters and the determination of hydrography and knickpoints were performed with geoprocessing techniques, using the spatial analysis and data manipulation tools of the software ArcGIS, 10.2.2 version We used 15 SRTM (Shuttle Radar Topographic Mission) images, version 3, band C, with a spatial resolution of 1 arcsecond (1"), approximately 30 meters, to generate a Digital Elevation Model (DEM) of the study area. This model was validated by means of kinematic GNSS (Global Navigation Satellite System) survey post-processed using the Precise Point Positioning (PPP) method. The intended morphometric and hypsometric analysis and the determination of hydrography and knickpoints of Mirim Lagoon basin were performed using the DEM SRTM. The hydrography was obtained with the Model Builder and the hydrologic tools of ArcGis. And the knickpoints were determined using the Knickpoint Finder, a script in Python language integrated to ArcGis ArcToolbox The results show that the use of SRTM data in GIS (Geographic Information Systems) allows the characterization of the watersheds, which is useful for water resources management and for environmental studies, and prove to be a practical and viable alternative to minimize cost and time in the work execution.

Creating 3D models of our surrounding world has seen a rapid increase in research and development over the last few years. A common method is to use laser scanners. Mapping is done either by ground based systems or airborne systems. With stationary ground-based laser scanning, or terrestrial laser scanning (TLS), it is possible to obtain high accuracy point clouds. But stationary TLS can often be a cumbersome and time-demanding task due to its lack of mobility. Because of this, much research has gone into mobilised TLS systems, referred commonly to as mobile laser scanning (MLS). Georeferencing point clouds to a world coordinate system is a difficult task in environments where global navigation satellite systems (GNSS) is unreliable. One such environment is forests, where the GNSS signal can be blocked, absorbed or reflected from the trees and canopy. Accurate georeference of points clouds for MLS systems in forests is difficult task that can be solved by using additional measurement instruments and post-processing algorithms to reduce the accumulation of errors, also known as drift. In this thesis a backpack-based MLS system to be used in forests was tested. The MLS system was composed of a GNSS, an inertial navigation unit (INS) and a laser scanner. The collected data was post-processed and analyzed to reduce the effects of detecting multiple ground layers and multiples of the same tree due to drift. The post-processing algorithm calculated tree and ground features to be used for adjusting the point cloud in the horizontal and vertical planes. The forest survey was done for an area roughly 40 meters in diameter. The MLS data was compared against TLS data as well as manual caliper data - where the caliper data was only measured in an area roughly 24 meters in diameter. The results indicated that the effects of multiple ground layers and multiple tree copies were removed after post-processing. Out of the total 214 TLS trees, 185 managed to be co-registered to MLS trees. The root mean square error (RMSE) and bias of the diameter at breast height (DBH) between the MLS andTLS data were 27.00 mm and -9.33 mm respectively. Co-registrationof the MLS and manual caliper data set gave 36 successful matches out of the total 43 manually measured DBH. The DBH RMSE and bias were 16.95 mm and -10.58 mm respectively. A Swedish TLS forest study obtained a DBH RMSE and bias (between TLS and caliper) of approximately 10 mm and +0.06 mm respectively. A Finnish backpack MLS forest study obtained a DBH RMSE and bias (between MLS and TLS) of 50.6 mm and +11.1 mm respectively. Evaluating the difference in radius at different heights along the tree stems between the MLS and TLS revealed a slight dependence on height, as the radius difference increased slightly closer to the stem base. The results indicated that backpack-based MLS systems has the potential for accurate lidar mapping in forests, and future development is of great interest to improve this system further.

This thesis examines the current implementations for the distribution of real-time GNSS data over IP networks such as the public Internet, focusing on two essential components of the system, data format and transport protocol. The provision of a suitable data format will allow users to take full advantage of the real-time GNSS data distribution system. Types of GNSS supported, message sizes, data rates, data precision levels, hardware and software support and possible future developments are investigated. An analysis is carried out on commonly known GNSS data formats, highlighting the most suitable standard for each evaluation criterion. A similar investigation is carried out on the transport protocols. An analysis is conducted on various design aspects of NTRIP and RT-IGS protocols, covering factors such as data latency, integrity, firewalls and proxy server compatibility and scalability. The analysis also covers the design aspects of the new draft Version 2 of NTRIP. The latter parts of this thesis report on the experiment results aimed at providing assessment of the current level of implementation of NTRIP. Data latency and integrity using NTRIP over the Internet are examined. Their impacts on users applications as the quality of real-time kinematic positioning is assessed. The results show that the performance of the system satisfies the rigorous requirement of the end-user application. The draft version of the new NTRIP indicates that UDP will be also supported. A similar investigation is carried out, providing the first experiment results on the new option. Tests using similar metrics, data latency and integrity, were carried out to verify the inherent differences between TCP and UDP. It was ascertained that, in most cases, UDP does offer improvement in terms of reduced latency over TCP. However this improvement is not significant enough to affect the performance of users applications tested. Compatibility tests were also carried out and the test results show that the new option experiences some compatibility issues with firewalls and wireless networks.

The availability of GPS signals is a major limitation for many existing and potential applications. Fortunately, with the development of Galileo by the European Commission (EC) and European Space Agency (ESA) and new funding for the restoration of the Russian GLONASS announced by the Russian Federation the future for satellite based positioning and navigation applications is extremely promising. This research primarily investigates the benefits of GNSS interoperability and GNSS/INS integration to Receiver Autonomous Integrity Monitoring (RAIM) from a geometrical perspective. In addition to these investigations, issues regarding multiple outlier detection and identification are examined and integrity procedures addressing these issues are proposed. Moreover, it has been shown how the same RAIM algorithms can be effectively applied to the various static and kinematic navigation architectures used in this research.

<p>Detta examensarbete utfördes under våren 2009 och avhandlar bestämning av fixpunkter i ett höjdnät med hjälp av statiska Global Navigation Satellite System (GNSS) mätningar. Ämnet är högaktuellt med tanke på att många kommuner står inför en övergång till Rikets Höjdsystem 2000 (RH 2000). Det kan vara ett problem vid en sådan övergång om det finns isolerade delar av det lokala höjdnätet som inte är anslutet till huvudnätet. Tidigare har den enda lösningen på ett sådant problem varit att genomföra ett höjdavvägningståg, ett både kostsamt och tidskrävande företag. Syftet med denna studie är att ge svar på hur noggrant det går att göra en höjdbestämning av fixpunkter med statisk GNSS-mätning.</p><p> Fältarbetet har utförts i Sandvikens kommun där ett antal höjdfixpunkter i RH 2000 nätet använts som referens vid GNSS-mätningar. Ett nät bestående av sju mätpunker etablerades i anslutning till RH 2000 höjdfixar. Fem av dessa användes sedan som passpunkter för att höjdbestämma två centralt belägna mätpunkter i nätet. För kontroll av mätningarna användes den kända avvägda höjden på de sökta punkterna. Mätningarna utfördes med fyra stycken Leica GX1230+ GNSS-mottagare som etablerades på punkterna i tre fyratimmarssessioner. Mätningarna utfördes i två kampanjer med tre veckors mellanrum.</p><p>Efterberäkning av GNSS- mätdata gjordes med Leica Geo Office 7 (LGO 7) och Surfer 8. Kontroll av resultaten gjordes genom matrisberäkningar i Microsoft Excel. Resultaten baseras på en sammanslagning av de båda mätkampanjerna. Avvikelserna visade sig ligga i ett spann på ca 3–5 mm ± punktmedelfelet (<strong>σ</strong>_H)lägre än de precisionsavvägda RH 2000 höjderna. Det faktum att samtliga GNSS-mätta höjder ligger 3–5 mm lägre än officiella RH 2000-höjder tyder på att ett systematiskt fel upptäckts. Slutligen, visar detta arbete att genom att kombinera frekvenser kan medelfelet bli så bra som 3 mm vid höjdbestämning med hjälp av statisk GNSS-mätning.</p>

Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2008.