Submitted by Haroudo Xavier Filho (haroudo.xavierfo@ufpe.br) on 2016-03-17T18:13:34Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) GILMARA DANNIELLE DE CARVALHO ROCHA_ DISSERTAÇÃO 2015.pdf: 3108174 bytes, checksum: c5307dded72886ffaf2f476a6333026d (MD5) / Made available in DSpace on 2016-03-17T18:13:34Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) GILMARA DANNIELLE DE CARVALHO ROCHA_ DISSERTAÇÃO 2015.pdf: 3108174 bytes, checksum: c5307dded72886ffaf2f476a6333026d (MD5) Previous issue date: 2015-03-06 / CNPq / Umas das maiores fontes causadoras de erro no posicionamento GNSS é a ionosfera, sendo que o efeito provocado por esta camada da atmosfera é um dos mais impactantes no processo de estimativa das coordenadas, principalmente para dados coletados com receptores de simples frequência. A modelagem matemática da refração ionosférica é complexa devido às variações diárias, sazonais, de curto e longo período, além de outros fenômenos que ocorrem na atmosfera, tal como a cintilação ionosférica. Em se tratando de posicionamento absoluto com receptores de simples frequência, seja Posicionamento por Ponto Simples (PP) ou Posicionamento por Ponto Preciso (PPP), estratégia adequada de correção dos efeitos ionosféricos devem ser adotadas. A correção da ionosfera para dados de simples frequência pode ser realizada a partir de modelo matemático, tal como o de Klobuchar, Mapas Globais ou Regionais da Ionosfera ou a partir da estimativa residual da ionosfera. Quando se tem disponível dados de duas frequências é possível utilizar a combinação ion-free, a qual permite eliminar os efeitos de primeira ordem da ionosfera. Contudo esta combinação faz com que as ambiguidades percam suas características de números inteiros, bem como realça outros níveis de ruído tal como o multicaminho. Uma possibilidade para atenuar os efeitos da ionosfera é a aplicação da estimativa dos efeitos residuais junto com as coordenadas incógnitas da estação e outros parâmetros. Neste caso, os efeitos da ionosfera podem ser tratados como um processo estocástico no Filtro de Kalman e se pode aplicar tal estratégia para dados de simples ou dupla frequência. Essa estratégia pode facilitar a solução das ambiguidades como inteiras e consequentemente permite a obtenção de resultados mais acurados no posicionamento geodésico. Dentro deste contexto, esta dissertação de mestrado apresenta a avaliação da acurácia do posicionamento absoluto GPS com aplicação de diferentes estratégias de correção da ionosfera. Foram realizados processamentos no modo PPP com dados GPS coletados em estações da RBMC em períodos de alta e baixa atividade solar para os anos de 2010 a 2013, onde se aplicou a correção da ionosfera advinda do modelo de Klobuchar, dos mapas globais (GIM – Global Ionospheric Map) e regionais (LPIM – La Plata Ionospheric Model), além da estimativa residual da ionosfera. As coordenadas estimadas foram comparadas com aquelas advindas da solução semanal SIRGAS-CON, a qual é dada atualmente em ITRF2008 e o Erro Médio Quadrático (EMQ), seja diário ou anual foi utilizado como medidor de acurácia. Ao aplicar as correções da ionosfera advinda dos mapas globais e regionais na estimativa de coordenadas no PPP utilizando somente medidas de código, observou-se melhoria de até 80% em relação ao PPP sem correção da ionosfera. O PPP com correção ionosférica advinda dos mapas regionais produziu melhorias diárias da ordem de 10% em relação ao uso dos mapas globais. Com base nas melhorias produzidas com a utilização do modelo ionosférico regional, foi proposta a modificação do modelo estocástico do ajustamento tendo em vista que somente o modelo funcional é afetado pelas correções ionosféricas advindas dos mapas. Com relação à estimativa residual da ionosfera foram realizados experimentos envolvendo medidas de código e fase na frequência L1 com geração de séries temporais anuais de coordenadas para diversas estações da RBMC, cuja acurácia alcançada foi da ordem de 10 cm no PPP com solução diária. / One of the largest sources of errors in the GNSS positioning is the ionosphere considering that the effect caused by that atmosphere layer is one of the most impacting in the coordinate estimation process, especially for data collected with single frequency receivers. Mathematical modeling of ionospheric refraction is complex due to daily variation in as well as, seasonal short and long period and also other phenomena occurring in the atmosphere such as ionospheric scintillation. Concerning the absolute positioning with single frequency receivers, whether Single Point Positioning (PP) or by Precise Point Positioning (PPP), appropriate strategy to correct the ionospheric effects should be adopted. The ionosphere correction for single frequency data can be performed from mathematical model, such as Klobuchar, Global or Regional Ionosphere maps or from residual ionosphere estimating. When one has available data from two frequencies it is possible to apply the ionosphere free combination which allows eliminating the first order ionosphere effects. However, this combination makes ambiguities lose its integer characteristics as well as amplify other noise levels as for instance multipath. One possibility to mitigate the ionosphere effects is the application of the ionosphere residual estimation along with coordinates station and other parameters. In this case, the ionosphere effects can be treated as a stochastic process in the Kalman filter where it is possible to apply that strategy for single or dual frequency data. This strategy can facilitate the integer ambiguities resolutions and consequently allows obtaining more accurate results in geodetic positioning. Inside this context, this master thesis presents the accuracy evaluation of the GPS absolute positioning by applying different strategies for ionosphere corrections. Processing was performed in PPP mode with GPS data collected in brazilizan RBMC stations in periods of high and low solar activities for the years 2010-2013, where it was applied ionosphere correction from Klobuchar model, global (GIM - Global Ionospheric Map) and regional (LPIM - La Plata Ionospheric Model) maps and the residual ionosphere estimation. The estimated coordinates were compared with those coming from SIRGAS-CON in a weekly solution which is currently given in ITRF2008 and Root Mean Square (RMS), either daily or annually, was used as accuracy measuring. When applying ionosphere corrections from global and regional maps in the PPP coordinates estimation using only code measurements, it was observed improvements of up to 80% comparing with PPP without ionosphere correction. The PPP with ionospheric correction coming from regional maps produced daily improvements of around 10% in relation to applying global maps. Based on improvements reached with corrections from regional ionospheric model, it was proposed the modification of the stochastic model for adjustment considering that only the functional model is affected by the ionospheric corrections coming from maps. Regarding the residual ionosphere estimation experiments were performed involving code and phase measurements in the L1 frequency with generation of coordinates annual time series considering the chosen RBMC stations whose accuracy achieve approximately 10 cm in PPP with daily solution.

Au cours de la dernière décennie, les drones ont été largement utilisés dans les domaines des applications civiles. La photogrammétrie aéroportée a trouvé place dans ces applications comme une solution efficace de modélisation 3D mais aussi comme un outil de mesure. Vinci-Construction-Terrassement est une entreprise privée spécialisée dans le secteur des Travaux Publics qui intègre les drones et la photogrammétrie comme une solution de cartographie et de métrologie de ses chantiers. Cet outil est très efficace, par exemple, pour le calcul des volumes de stocks ou pour le suivi temporel de zones spécifiques avec un risque de glissement de terrain. Le but de ce travail est d’arriver à un géo-référencement direct des images acquises par la caméra lors du vol en s’appuyant uniquement sur un récepteur GPS embarqué. Le système utilisé doit être de faible coût et par conséquent le traitement des données est adapté à cette contrainte / Over the last decade, drones have been largely used for civil applications. Airborne photogrammetry has found place in these applications as a modeling and a measuring tool. Vinci-Construction-Terrassement is a private company of public building and works sector that integrates drones and photogrammetry as a mapping solution and metrology investigation on its sites. This tool is very efficient for the calculation of stock volumes for instance, or for time tracking of specific areas with risk of landslides. The aim of the present work is to do direct georeferencing of images acquired by the camera leaning on an embedded GPS receiver. The UAS used needs to be low cost and therefore data processing is adapted to this constraint

The Global Navigation Satellite System (GNSS), in the last few years, has been supporting the development of mobile telephony and the expansion of electronic equipments (GNSS receivers) to promote a revolution in geodetic surveys in real time. In this context, it becomes important the technique of positioning Real Time Kinematic (RTK) with the use of differential corrections transmitted by the protocol named Networked Transport of RTCM via the Internet Protocol (NTRIP), from a reference station via Internet. It is aimed, in this research, the evaluation of the precision of this technique for different lengths of baseline, and also the use of different numbers of trace periods. Then, three-dimensional coordinates of 10 stations (DEM) were used, they were also located in three municipalities of Rio Grande do Sul, which were traced by the static post-processed (static PP) method, which helped as being a reference in comparison with technique RTK / NTRIP, that used the correlations of the Brazilian Network for Continuous Monitoring of the GNSS Systems in real time - (RBMC-IP). The results showed that there was resolution of the ambiguities in nine seasons at baseline greater than 54 km, and that the precision values showed no difference greater than 0.041 m in the horizontal component and 0.083 m in the vertical component. In addition, between the numbers of the tested periods (5,10,30, 60 and 120 periods) for the method RTK / NTRIP, the tested period that had the best average precision of the horizontal component was the 120 one (0.01 m), and for the vertical component was considered the five periods number as the most appropriated (0.02 m). Hence, it was proved the reliability of the technique RTK / NTRIP (RBMC-IP) in baselines of until 54 km, showing that it can be used for topographical surveys in areas with wireless Internet or cellular services such as GPRS, GSM and 3G. / O Sistema Global de Navegação por Satélite (GNSS) nos últimos anos vem se apoiando no desenvolvimento da telefonia móvel e no avanço da eletrônica dos equipamentos (receptores GNSS) para promover uma revolução nos levantamentos geodésicos em tempo real. Neste contexto, se destaca a técnica de posicionamento Real Time Kinematic (RTK) usando correções diferenciais transmitidas pelo protocolo Networked Transport of RTCM via internet Protocol (NTRIP), a partir de uma estação de referência via internet. O objetivo deste trabalho foi avaliar a precisão desta técnica para diferentes comprimentos de linha de base e com o uso de diferentes números de épocas de rastreio. Para isso, foram utilizadas as coordenadas tridimensionais de 10 estações (marcos), localizadas em três municípios do estado do Rio Grande do Sul, rastreadas pelo método relativo estático pós-processado (estático PP), o qual serviu de referência na comparação com a técnica RTK / NTRIP, que utilizou de correções da Rede Brasileira de Monitoramento contínuo dos Sistemas GNSS em tempo real (RBMC-IP). Os resultados mostraram que houve resolução das ambiguidades em nove estações numa linha de base superior a 54 km e que os valores de acurácia não apresentaram diferença superior a 0,041 m na componente horizontal e 0,083 m na componente vertical. Além disso, entre os números de épocas testados (5, 10, 30, 60 e 120 épocas) para o método RTK / NTRIP, aquele que apresentou a melhor média de acurácia horizontal foi o de 120 épocas (0,01 m) e para a componente vertical o melhor resultado foi alcançado com o número de 5 épocas rastreadas (0,02 m). Deste modo, foi comprovada a confiabilidade da técnica RTK / NTRIP (RBMC-IP) em linhas de base de até 54 km, podendo ser utilizada para levantamentos topográficos em locais providos por Internet wireless ou serviços de telefonia celular tais como, GPRS, GSM e 3G.

Dans le but d’améliorer la disponibilité des services fournis par un récepteur, la conception d’un récepteur GNSS permettant de recevoir plusieurs signaux de toutes les bandes simultanément semble être la solution. Une architecture à sous échantillonnage RF optimisée de type SDR (Software Defined Radio) comportant un étage RF intégrable et reconfigurable et un étage de traitement numérique avec une implémentation logicielle du traitement en bande de base est défini pour ce récepteur GNSS, tout en répondant aux exigences des spécifications des standards GNSS : des réseaux radio cellulaires : GPS, Glonass, Galileo, Beidou. Un choix des composants discrets suite au dimensionnement system est effectué et ceci pour installer un prototype de validation expérimental. Ensuite nous nous s’intéressons à la caractérisation de la chaine RF afin d’étudier les limitations causés par la non linéarité et d’étudier la stabilité du prototype proposé. Un étage de traitement numérique des signaux IF, capturés à la sortie de l’ADC, est implémenté sous Matlab. L’acquisition de ces données permet la détermination des satellites visible à un instant donné qui nous permet éventuellement la détermination d’une position / In order to improve the availability of services provided by a receiver, designing a GNSS receiver to collect multiple signals from all bands simultaneously seems to be the solution. An optimized software-defined RF (SDR) sub-sampling architecture with an integral and reconfigurable RF stage and a digital processing stage with a software implementation of the baseband processing is defined for this GNSS receiver, while meeting the requirements GNSS standards specifications: cellular radio networks: GPS, Glonass, Galileo, Beidou. Many discrete components are selected after system dimensioning. Thus, experimental validation prototype is installed. Then we are interested in the characterization of the RF front-end in order to determine the limitations caused by the nonlinearity and to study the stability of the proposed prototype. A stage of digital processing of the IF signals, captured at the ADC output, is implemented under Matlab software. The acquisition of these data allows the determination of satellites visible at a given instant that allows us to determine a position

Die Veränderungen des Antarktischen Eisschildes (AIS) haben einen entscheidenden Einfluss auf den Meeresspiegel. Für Prädiktionen zukünftiger Szenarien des globalen Klimawandels ist das Verständnis der zugrundeliegenden Prozesse und damit die Beobachtung gegenwärtiger Veränderungen unabdingbar. Mit Hilfe von Satellitenaltimetrie lässt sich die Massenbilanz des AIS großflächig, hochaufgelöst und kontinuierlich ermitteln. Da viele Prozesse jedoch auf sehr langen Zeitskalen ablaufen, ist es das Ziel dieser Arbeit, durch Validierung, Kalibrierung und Kombination der Messungen verschiedener Altimetermissionen die Zeitreihen der Beobachtungen maximal zu verlängern. Nur so lassen sich interannuale Variationen vom Langzeittrend trennen, was entscheidend für das Verständnis der Prozesse der Oberflächenmassenbilanz und der Eisdynamik ist. Die Ausgangsdaten dieser Arbeit bilden altimetrische Höhenmessungen des AIS. Zur Analyse ihres Genauigkeitspotenzials und um Kalibrierfehler aufzudecken, werden diese Messungen mit unabhängigen In-situ-Daten validiert. In dieser Arbeit wurde hierfür ein umfangreicher Datensatz von kinematischen GNSS-Profilen verwendet, welche zwischen 2001 und 2015 beobachtet wurden und mit Profillängen von bis zu 1700 km das gesamte topografische Spektrum des Eisschildes abdecken. Neben der anspruchsvollen differenziellen Auswertung der GNSS-Profile mit Basislinienlängen von über 1000 km erfordert auch die Reduktion der Höhe der Antenne auf die Schneeoberfläche aufgrund des Einsinkens der Zugmaschinen in die oberen Firnschichten besondere Berücksichtigung. Anhand dieser Daten wurden Radaraltimetermessungen in unterschiedlichen Prozessierungsvarianten verglichen, um den Einfluss der Wahl der Auswerteansätze zu quantifizieren. Die Genauigkeit der Radaraltimetrie von Eisschilden wird dominiert durch das Retracking zur Ableitung der exakten Signallaufzeit und durch die Methode der Korrektion topografischer Einflüsse. Die Validierung zeigt, dass durch einen schwellwertbasierten Retracker und die Relokation der Messung zum satellitennächsten Punkt die höchste Genauigkeit erreicht wird. Optimierte Varianten dieser Ansätze wurden zur konsistenten Reprozessierung aller Radarmessungen verwendet, wodurch nicht nur ein einheitlicher Datensatz geschaffen, sondern auch die Genauigkeit der meisten Messungen um etwa 50% verbessert wurde. Auch die Laseraltimetermessungen von ICESat wurden anhand der GNSS-Profile kalibriert. Hier wurden Laserkampagnenbias bestimmt und korrigiert, welche andernfalls abgeleitete Höhenänderungsraten um etwa 1,2±0,3 cm/a verfälscht hätten. Zur gemeinsamen Auswertung der Altimetermissionen Seasat, Geosat, ERS-1, ERS-2, Envisat, ICESat und CryoSat-2 wurde der Ansatz der Wiederholspuranalyse verwendet und noch erweitert, um spezifische Charakteristika unterschiedlicher Missionen entsprechend berücksichtigen zu können. Die hieraus abgeleiteten Zeitreihen beinhalten noch die Kalibrierbias der jeweiligen Messungen, welche im Anschluss unter Beachtung von Aspekten technikspezifischer Abtastung des Geländes und zeitlicher Distanz verschiedener Missionen schrittweise bestimmt und korrigiert werden. Das Ergebnis dieser kombinierten Auswertung bilden monatlich aufgelöste Zeitreihen von Höhendifferenzen gegenüber einer Referenzepoche auf einem Gitter von 10x10 km. Die Validierung mit kinematischen GNSS-Profilen, wie auch mit flugzeuggestützten Lasermessungen, bestätigt die beobachteten Höhenänderungen der kombinierten Zeitreihen und zeigt, dass auch die abgeleiteten Fehlermaße realistische Abschätzungen der Unsicherheit darstellen. Nach Korrektion der Höhenänderungen um Ausgleichsbewegungen der festen Erde und der Umrechnung in eine Massenänderung lässt sich aus diesen Beobachtungen die Massenbilanz verschiedener Regionen des Antarktischen Eisschildes ableiten. Aus den Ergebnissen geht hervor, dass der beobachtete Teil des AIS nördlich von 81,5° südlicher Breite im Schnitt 85±16 Gt/a zwischen 1992 und 2017 an Masse verloren hat. Die Zeitreihen zeigen, dass diese Rate sich vor etwa 10 Jahren nochmals deutlich beschleunigte, so dass der Massenverlust zwischen 2010 und 2017 137±25 Gt/a betrug. Die Unterteilung in verschiedene Teilregionen des Eisschildes zeigt, dass diese Verluste nahezu vollständig der Westantarktis und der Antarktischen Halbinsel zuzuschreiben sind, während sich in der Ostantarktis Regionen mit Massenverlusten und mit Massenzuwächsen gegenseitig ausgleichen. Aus der Analyse der altimetrischen Beobachtungen der küstennahen Regionen der Ostantarktis, welche bis 1978 zurückreichen, geht hervor, dass der Trend über 25 Jahre sich auch vor 1992 in ähnlicher Weise fortsetzen lässt, so dass hier tatsächlich von einem Langzeittrend gesprochen werden kann. Allerdings wird dieser Trend oftmals durch interannuale Variationen überlagert, was sich aus den monatlichen Zeitreihen gut ablesen lässt und entscheidend für die Interpretation ist. Ein Vergleich mit Massenzeitreihen aus gravimetrischen Beobachtungen und Modellierungen der Oberflächenmassenbilanz zeigt eine hohe Konsistenz der Ergebnisse unterschiedlicher Beobachtungsverfahren, birgt jedoch auch Hinweise, wo Annahmen über die zugrunde liegenden Prozesse zu hinterfragen sind. Somit liefert dieser Vergleich einen wichtigen Beitrag zum Verständnis der Prozesse der Eismassenbilanz des AIS. Die Grundlage der vorliegenden kumulativen Dissertation bilden zwei wissenschaftliche Publikationen. Die erste Publikation befasst sich mit der Validierung und Kalibrierung unterschiedlicher Altimeterprodukte mit In-situ-Messungen und beinhaltet in diesem Zusammenhang auch Details zur Auswertung der kinematischen GNSS-Profile, welche die Grundlage dieser Untersuchungen bilden. Die zweite Publikation baut auf den Ergebnissen der vorherigen Studie auf, beschreibt die Reprozessierung und die Kombination der Daten verschiedener Altimetermissionen und analysiert die Ergebnisse dieser Multimissionszeitreihen Antarktischer Eishöhenänderungen. Insgesamt soll diese Arbeit einen Beitrag zum verbesserten Verständnis der Veränderungen des AIS im Zuge des globalen Klimawandels liefern. Darüber hinaus zeigt sie auch weiteres Potenzial für zukünftige Arbeiten auf.:Zusammenfassung Abstract 1. Einführung 1.1. Die polaren Eisschilde 1.2. Satellitengestützte Beobachtungsverfahren 2. Satellitenaltimetrie 2.1. Messprinzip 2.2. Komponenten der Oberflächenhöhenbestimmung 2.2.1. Orbitbestimmung 2.2.2. Distanzmessung 2.3. Missionen 2.4. Satellitenaltimetrie über Eisschilden 2.4.1. Analyse des Rückkehrsignals 2.4.2. Topografiekorrektion 2.4.3. Interferometrischer SAR-Modus 2.4.4. Bias bei Eisaltimetrie 3. Bestimmung von zeitlichen Variationen der Eisoberflächenhöhe 3.1. Methoden zur Bestimmung von Höhenänderungen 3.2. Kombination unterschiedlicher Missionen 4. Validierung 4.1. Messunsicherheiten und Arten der Validierung 4.2. Absolute Validierung mit kinematischen GNSS-Profilen 4.3. Validierung der Bestimmung von Höhenänderungen 5. Geophysikalische Interpretation 5.1. Von Höhenänderungen zur Eismassenbilanz 5.2. Vergleich unterschiedlicher Beobachtungsverfahren 6. Publikationen PI. Validierung von Satellitenaltimetrie mittels kinematischem GNSS PII. Multimissions-Satellitenaltimetrie über vier Jahrzehnte 7. Zusammenfassung und Ausblick Literaturverzeichnis / Changes of the Antarctic Ice Sheet (AIS) have a significant impact on sea level. To predict future scenarios of global climate change, it is essential to understand the contributing processes and, therefor, to observe current changes. Large scale, high resolution and continuous mass balances of the AIS can be obtained with the help of satellite altimetry. As many processes here act over very long temporal scales, the goal of this work is to validate, calibrate and combine the measurements of different altimetry missions in order to obtain time series which are as long as possible. Only such long-term observations allow to separate interannual variations from the long-term trend, which is crucial to understand the processes of surface mass balance and ice dynamics. Altimetric observations of elevation of the AIS are the basic data used in this work. In order to analyze their accuracy and precision, these measurements are validated using independent in situ observations. Here, an extensive set of kinematic GNSS-profiles was utilized for this purpose. These profiles were observed between 2001 and 2015 and, with lengths of up to 1700 km, they cover the whole spectrum of ice sheet topography. To obtain high precision surface elevation profiles, not only the demanding differential GNSS-processing with baseline lengths of more than 1000 km needs to be treated very carefully, also the reduction of the antenna height measurement to the snow surface requires special attention as the heavy vehicles sink into the upper firn layers in some regions. With the help of this data set, radar altimetry measurements in different processing versions are compared in order to quantify the influence of the choice of methods to derive the surface elevation. The uncertainty of a radar altimetry measurement of an ice sheet is dominated by the method of retracking, which is used to defined the exact signal travel time, and the methodology to correct for topographic effects. The validation shows that a threshold based retracker and the method of relocating the measurement to the point of closest approach provides the highest accuracy and precision. All radar altimetry measurements have been consistently reprocessed using optimized versions of these approaches. This provided a uniform data basis for their combination and, at the same time, improved the accuracy of these measurements by about 50%. Also the laser measurements of ICESat were calibrated using these profiles. This helped to correct for the laser campaign biases, which, otherwise, would distort any inferred surface elevation rate by 1.2±0.3 cm/yr. The joint processing of the missions Seasat, Geosat, ERS-1, ERS-2, Envisat, ICESat and CryoSat-2 was performed using the repeat altimetry method. Here, several extensions of this approach were developed to cope with the characteristics of the different missions. The derived time series still contained calibration biases, which were determined and corrected for in the following stepwise approach, taking into consideration aspects as the topography sampling of different techniques and the temporal sequence of the missions. The result of this combination are monthly time series of elevation changes with respect to a reference epoch, gridded on a 10x10 km raster. The validation with kinematic GNSS-profiles, as well as with airborne laser measurements, confirms the elevation changes from the multi-mission time series and proves that also the uncertainty estimates of these results are realistic. The mass balance of different regions of the Antarctic Ice Sheet was obtained by correcting the surface elevation changes for changes of the underlying solid earth and transforming the results into mass. The obtained data shows that the observed part of the AIS north of 81.5° southern latitude lost an average amount of mass of 85±16 Gt/yr between 1992 and 2017. The time series reveal that this rate accelerated about 10 years ago, leading to a rate of 137±25 Gt/yr between 2010 and 2017. Individual time series of different parts of the ice sheet show that these losses originate almost completely from the West Antarctic Ice Sheet and the Antarctic Peninsula. In contrast for East Antarctica, regions with negative and positive mass balances compensate each other almost entirely. In coastal East Antarctica, where the altimetric observations range back until 1978, the results show that the rate over 25 years continues very similarly also before 1992, which proves that the rates, observed here, can be considered as long-term rates. However, the monthly time series also reveal, that this trend is superimposed by interannual variations, which is crucial for the interpretation of these elevation changes. A comparison with mass time series from gravimetric observations and models of surface mass balance demonstrates the high consistency of the results. On the other hand, this comparison also reveals some discrepancies, indicating where the assumptions about the underlying processes need further improvements. Hence, this comparison provides new insights for the understanding of the processes contributing to the mass balance of the AIS. This dissertation is based on two scientific publications. The first paper describes the validation and calibration of different products of altimetry using in situ data. Therefore, it also contains details towards the processing of kinematic GNSS-profiles which form the basis of this investigation. Based on these results, the second paper describes the reprocessing and the combination of different altimetry missions and analyzes the results of these multi-mission time series of Antarctic surface elevation changes. In conclusion, this work aims to contribute to a better understanding of the changes of the AIS under a changing climate. Furthermore, it also points out potential aspects for further improvements.:Zusammenfassung Abstract 1. Einführung 1.1. Die polaren Eisschilde 1.2. Satellitengestützte Beobachtungsverfahren 2. Satellitenaltimetrie 2.1. Messprinzip 2.2. Komponenten der Oberflächenhöhenbestimmung 2.2.1. Orbitbestimmung 2.2.2. Distanzmessung 2.3. Missionen 2.4. Satellitenaltimetrie über Eisschilden 2.4.1. Analyse des Rückkehrsignals 2.4.2. Topografiekorrektion 2.4.3. Interferometrischer SAR-Modus 2.4.4. Bias bei Eisaltimetrie 3. Bestimmung von zeitlichen Variationen der Eisoberflächenhöhe 3.1. Methoden zur Bestimmung von Höhenänderungen 3.2. Kombination unterschiedlicher Missionen 4. Validierung 4.1. Messunsicherheiten und Arten der Validierung 4.2. Absolute Validierung mit kinematischen GNSS-Profilen 4.3. Validierung der Bestimmung von Höhenänderungen 5. Geophysikalische Interpretation 5.1. Von Höhenänderungen zur Eismassenbilanz 5.2. Vergleich unterschiedlicher Beobachtungsverfahren 6. Publikationen PI. Validierung von Satellitenaltimetrie mittels kinematischem GNSS PII. Multimissions-Satellitenaltimetrie über vier Jahrzehnte 7. Zusammenfassung und Ausblick Literaturverzeichnis

Målsättningen med examensarbetet är att utvärdera en metod för att upprätta en kommunikationslänk från en mobil satellitterminal till en geostationär kommunikationssatellit utan kännedom om satellitterminalens position på jordytan. Målsättningen är intressant då GNSS-operatörer (främst i det allmänna USA-drivna GPS-systemet men möjligen även i de tillkommande franska, kinesiska, ryska och europeiska systemen) begränsar den allmänna tillgängligheten av taktiska/strategiska skäl vid konflikter och kriser. Därtill att allmänna globala navigationssatellittjänster, GNSS-system, ofta bygger på mottagningsantenner med låg riktverkan vilka kan störas ut av lokala störningskällor. En mobil satellitterminal blir därmed beroende av manuell inmatning av riktningsvinklar för att upprätta nya satellitkommunikationslänkar. Systemet blir då mycket sårbart. I denna rapport återges resultat från mätserier inhämtade vid satellitterminalinstallationer utförda i Frankrike, Indonesien, Kanada, Polen, Sverige och USA. / The objective of the thesis is to evaluate a method for establishing a communication link from a mobile earth station to a geostationary communication satellite without prior knowledge of the position of the earth station. The objective is interesting as the GNSS-operators (mainly in the United States-run GPS-system, but possibly also in the French, Chinese, Russian and European systems) limits the general availability of tactical/strategic reasons during conflicts and crises. Furthermore, general GNSS-systems are based on receiving antennas with low directivity which can be disrupted by a local opponent or by other local sources of interference. A mobile earth station, lacking proper positioning information, depends on manual entry of directional angles to establish new satellite communication links. The system then becomes very vulnerable. This report evaluates measurement data gathered from deployed satellite terminal installations in Canada, France, Indonesia, Poland, Sweden and the U.S.

Network-RTK is a method of relative measuring using GNSS that provides users in alarge area with an easy way obtaining low uncertainties in their measurements. Regularnetwork-RTK does not meet the requirements of the Swedish Transport Administration(STA) regarding its larger and/or more complex projects, leading to the concept ofproject-based network-RTK being introduced in Sweden by the STA, in collaborationwith the network-RTK service provider SWEPOS back in 2004. This concept improvesupon regular network-RTK by decreasing the uncertainties and increasing reliabilitieswithin the project area. SWEPOS has since the collaboration back in 2004 supplied theSTA with project-based network-RTK services.The market is not the same today as it was in 2004 and there are more service providersactive in Sweden. This thesis intends to find out if this new market means that there areother alternatives to SWEPOS with regards to the STA’s requirements for project-basednetwork-RTK. This is done through a technical comparison of the different serviceprovider’s measurement uncertainties and their measurement accuracies as well as acomparison of their surrounding infrastructure and the subjective user experience.Similar studies have been conducted before (Edwards et al., 2010) (Martin andMacGovern, 2012) (Saeidi, 2012), but never in Sweden nor with SWEPOS as one of theservice providers as it is only available in Sweden. Neither have they had a focus onmeasurement uncertainties and accuracies in a project-based network-RTK net. Theyhave all concluded that there were no significant differences between any of the serviceproviders compared, in both the measurement uncertainties and accuracies.For the technical part of this thesis, measurements were conducted at four sites: two atdifferent locations within the area of a former, STA project-site, one within the regularnet and the final site outside the entire net, with the amount of collected data varying forthe different sites. Five different GNSS receivers of different brands were used for themeasurements to make it as general as possible.The results show that there are slight differences in the height uncertainty, but the scopeof this thesis does not permit the full correlation study needed to determine if thesedifferences are significant. There does not seem to be any differences in the accuracies ofthe service provider. Some of the sites with less data collected show contradictoryevidence to this statement, but it is deemed that these deviations are more likely relatedto something other than the service providers, such as human interference or errors.Large differences exist in the user experience and surrounding infrastructure, an areawhere SWEPOS at the moment has a clear lead. This is believed to be due to SWEPOSprimarily being a network-RTK service provider and thus allocating more resources andpersonnel, whilst the other service providers also serve as equipment vendor andmaintainers.Combining the two comparison parts leads to the overall conclusion that with theservice providers in their current state with the requirements of the STA specified intheir current state, only SWEPOS is a viable alternative as a supplier of project-basednetwork-RTK. But this is something that could change with relative ease depending on ifthe other service providers allocate more resources. / Nätverks-RTK är en metod för relativ mätning med hjälp av GNSS som ger användare istora områden ett enkelt sätt att förbättra osäkerheterna i sina mätningar. I början av2000 talet då frågan om alternativa lösningar till stomnät på marken aktualiseradesuppfyllde inte tillgängliga nätverks-RTK-lösningar Trafikverkets (TrV) krav påmätningar när det gäller dess större och/eller mer komplexa projekt. Något som leddetill att konceptet projektbaserad nätverks-RTK infördes i Sverige av TrV i samarbetemed tjänsteleverantören SWEPOS 2004. Detta koncept förbättrar vanlig nätverks-RTKgenom att minska osäkerheterna ytterligare och öka tillförlitligheten inom ett mindreprojektområde. SWEPOS har sedan detta samarbete 2004 levererat projektbaseradenätverks-RTK tjänster till TrV.Marknaden är inte samma dag som den var 2004 och det finns fler verksammatjänsteleverantörer i Sverige. Detta examensarbete avser att ta reda på om denna nyamarknad innebär att det finns andra alternativ till SWEPOS med avseende på de kravTrV har på projektbaserad nätverks-RTK. Något som sker genom en teknisk jämförelseav de olika tjänsteleverantörernas mätosäkerheter och deras noggrannheter samt enjämförelse av deras omgivande infrastruktur och den subjektiva användarupplevelsen.Liknande studier har gjorts tidigare (Edwards et al., 2010) (Martin och MacGovern2012) (Saeidi, 2012), men aldrig i Sverige och med SWEPOS som ett avjämförelseobjekten. De har inte heller haft fokus på mätosäkerheter och noggrannheterunder projektbaserade nätverks-RTK förhållanden. De har alla haft samma slutsats: attdet inte finns några signifikanta skillnader mellan de jämförda tjänsteleverantörerna.För den tekniska jämförelsen har mätningar utförts på fyra platser: två inom ettbefintligt TrV projektområde, en i det ordinarie nätet och den sista utanför hela nätet,där den insamlade datamängden varierar för de olika platserna. Fem olika GNSSmottagareav olika märken användes för att göra mätningarna så allmänna som möjligt.Resultaten visar att det finns små osäkerhetsskillnader i höjd, men för att avgöra omdessa skillnader är signifikanta eller ej så skulle en fullständig korrelationsanalys av deolika tjänsteleverantörerna behövas, något som inte ryms inom detta arbete. Det verkarinte heller finnas några signifikanta skillnader i noggrannhet hos tjänsteleverantören.Några av platser med mindre mängd insamlad data uppvisar motsägande resultat, mendetta bedöms bero mer på andra faktorer än tjänsteleverantörer i sig, såsom mänskligpåverkan etc.Användarupplevelsen och tjänsteleverantörernas omgivande infrastruktur uppvisarstörre skillnader, där SWEPOS för tillfället har ett klart övertag. Detta tros bero påSWEPOS främst är en tjänsteleverantör av nätverks-RTK och därmed har merdedikerade resurser och personal, men de andra tjänsteleverantörerna även agerarleverantörer/försäljare av utrustning.En kombination av de två jämförelsedelarna leder till en mer generell slutsats att medalla tjänsteleverantörer i sina nuvarande tillstånd alternativt utan en eventuellomformulering av TrVs krav, är enbart SWEPOS ett alternativ som leverantör avprojektbaserad nätverks-RTK lösningar till TrV. Men detta är något som kan förändrasmed relativ snabbt beroende på om andra tjänsteleverantörerna avsätter mer resursereller om kraven formuleras om.

GNSS-teknik ersätter i allt högre grad terrester mätteknik, dels på grund av sin enkelhet och dels på grund av att den är mindre kostsam än traditionella metoder. En vanlig förekommande GNSS-teknik är RTK (Real Time Kinematic) som är en teknik som beräknar en position i realtid genom bärvågsmätning. Inom RTK-mätning finns det olika tekniker att utöva; enkelstations-RTK (ERTK) och nätverks-RTK (NRTK). I studien undersöktes kvaliteten och lägesosäkerhet på höjdbestämningsdata erhållen från dessa metoder. En envägs variansanalys (ANOVA) användes för att undersöka om det fanns en signifikant skillnad mellan de genomsnittliga avvikelser som erhölls från mätmetoderna. Mätmetoderna utfördes över två punkter med känd höjd som fastställdes tidigare med ett dubbelavvägningståg. ERTK och NRTK varvades med en observationstid på 20 minuter med positioneringsintervall på 3 sekunder. Tidseparationen mellan mätningarna varade i 30 minuter och sammanlagt utfördes 5 mätserier med 400 observationer i varje serie. Grova fel eliminerades genom att kassera värden som föll utanför 3σ-gränsen. Resultaten från ERTK-mätningarna visade att punkten kunde höjdbestämmas med en lägesosäkerhet på 22 mm och en mätosäkerhet på 32 mm (2σ) för samtliga mätserier tillsammans. Internt varierade lägesosäkerheten 13–28 mm mellan serierna. NRTK mätningarna erhöll en total lägesosäkerhet på 14 mm och en mätosäkerhet på 24 mm (2σ). Från enskilda mätserier erhöll serie 3 den lägsta lägesosäkerheten på 9 mm, och serie 4 den högsta med 18 mm. Generellt visade NRTK-metoden lägre och jämnare avvikelser från referensdata än ERTK, resultatet kan dock ha blivit påverkat av basens läge i relation till ett närliggande träd. ANOVA-testet visade att det fanns en signifikant skillnad mellan mätserierna (p =0,00) per enskild metod, men skillnaden av medelavvikelserna mellan dessa metoder var inte signifikanta (p =0,115). Resultatet från denna studie är viktig med avseende på kvalitetsutvärdering av olika GNSS-metoder och kan användas som underlag för beslut om tillämpad metod för andra mätuppdrag. / A quality survey was performed on the position accuracy of two GNSS-methods (single station-RTK and network-RTK) for height determination, and a one-way analysis of variance (ANOVA) was used for statistical investigation of differences in the spread of height deviations. The GNSS-methods were applied on a reference point, which was determined prior with leveling, and measured with 20 minutes observation time and 30 minutes time separation, resulting in 5 series containing 400 observations each from respective method. The ANOVA test was performed by grouping the height deviations with respect to the measurement series, as well as the mean deviations with respect to the methods. Height determination with the ERTK method showed a total positional uncertainty of 22 mm (13-28 mm between the series) and a measurement uncertainty of 32 mm (2σ). Results obtained with NRTK showed a total positional uncertainty of 14 mm (9-14 between the series) and a total measurement uncertainty of 24 mm (2σ). The statistical tests showed that the differences between the measurement series for individual methods were significant (p = 0,000) but that the mean deviations between the methods were not (p = 0,115). NRTK obtained a lower positional uncertainty than ERTK measurements in this study, and the ANOVA test showed that there was no significant difference in the distribution of the mean deviations between the measurement methods. This study is important with regard to quality evaluation of different GNSS-methods and can be used as a basis for deciding on the applied measurement method.

No description available.

There are a number of global navigation satellite systems (GNSS), in use or planed, which are used for navigation on earth but also for autonomous navigation of satellites in low earth orbit (LEO). It would be desirable to also have autonomous navigation in geosynchronous earth orbit (GEO) to reduce costs and make it possible to get higher accuracy on the position of the satellite. One part of the navigation system is the GNSS antenna which is examined in this master thesis. The specifications of the antenna were first decided and then three antenna alternatives were investigated in greater detail: a monofilar helix antenna, a three element circular array antenna and a twelve element circular array antenna. The result was that they would all work as a GNSS antenna in GEO but none could be judged to be the best under all circumstances. The size requirement for the mission and the used GNSS receiver would primarily decide which fits the mission best. / Det finns ett antal världstäckande navigeringssystem (GNSS), i användning och planerade, som används för navigation på jorden fast också för autonom navigation för satelliter i låg bana runt jorden. Det skulle också vara önskvärt att använda autonom navigation för satelliter i geostationär omloppsbana (GEO) för att reducera kostnaden och få högre positions noggrannhet. En del av navigationssystemet är GNSS antennen vilken är undersökt i detta examensarbete. Specifikationerna för antennen bestämdes först och sedan undersöktes tre olika antennalternativ i detalj: en monofilär helixantenn, en tre elements cirkulär gruppantenn och en tolv elements cirkulär gruppantenn. Resultatet var att alla alternativen skulle fungera som en GNSS antenn i GEO-bana fast inget av alternativen är bäst i alla förhållanden. Storlekskraven för uppdraget och vilken GNSS mottagare som skall användas påverkar vilket av alternativen som passar uppdraget bäst.