• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 138
  • 113
  • 18
  • 14
  • 8
  • 7
  • 5
  • 5
  • 3
  • 3
  • 3
  • 2
  • 2
  • 2
  • 2
  • Tagged with
  • 376
  • 376
  • 210
  • 163
  • 128
  • 70
  • 66
  • 65
  • 51
  • 50
  • 47
  • 43
  • 38
  • 36
  • 36
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
331

Approches régionales de la susceptibilité torrentielle dans les Alpes du Sud / Debris-flow susceptibility assessment at the regional scale of the Southern French Alps

Bertrand, Mélanie 20 May 2014 (has links)
L'objectif de cette thèse est de produire une méthodologie de restitution spatiale de la susceptibilité torrentielle à une échelle régionale. Les méthodes géomatiques et statistiques mises en œuvre visent à intégrer différents facteurs de prédisposition au phénomène de laves torrentielles, en particulier les caractéristiques morphométriques des tronçons et de leur bassin versant et leur potentiel de fourniture sédimentaire.La définition de modèles statistiques robustes a permis de prédire l'activité torrentielle à partir de la morphométrie des tronçons et de leur bassin versant, et permettent la discrimination des processus de laves torrentielles et de charriage.Au niveau des zones sources, le second facteur de prédisposition qu'est la disponibilité sédimentaire, est cartographié à partir de l'analyse des orthophotographies infrarouges de l'IGN©, puis est combiné à la susceptibilité morphométrique dans un SIG de manière experte. Ainsi, le potentiel sédimentaire des bassins versants sources vient pondérer la probabilité d'activité de lave torrentielle établie à partir du potentiel morphométrique dans le but de prédire la susceptibilité au déclenchement. Plus aval, la prédisposition à la propagation de laves torrentielles dépend des caractéristiques morphométriques et est également contrôlée par la susceptibilité torrentielle des biefs situés juste en amont (approche réseau). L'application de la démarche dans les Alpes du Sud a été validée avec 50 observations expertes.Cette thèse a conduit à la production des cartes des zones de déclenchement de laves torrentielles, et à l'identification de leur zone de propagation potentielle, intégrées à une plateforme de services (projet RHYTMME, Irstea et Météo-France). Elles peuvent être superposées avec les aléas de précipitations pour identifier les secteurs susceptibles à l’activité de laves torrentielles lors d'événements de précipitations de forte intensité. / The main objective of this thesis is to produce a methodology spatially characterizing the debris flow susceptibility at a regional scale. The methods used are based on geomatic and statistic fields and aim at integrating the predisposing factors to debris flow activity, especially the morphometry and the potential sediment availability.Robust statistical models allowed to predict the debris flow activity based on the morphometry of the reaches and their catchments in order to discriminate the bedload transport from the debris flow processes.In source areas, the second predisposing factor, i.e. the sediment availability, was first mapped thanks to the analysis of infrared orthophotos (IGN©) and then expertly combined with the morphometric susceptibility within a GIS. The sediment availability potential of upland catchment consequently weights the probability of debris flow activity (firstly established from the morphometric characteristics) in order to predict the susceptibility to debris-flow triggering. More downstream, the predisposition to debris flow propagation depends on morphometric characteristics and is also controlled by the debris flow susceptibility of the upstream reaches. In the Southern French Alps, the entire approach has been validated with 50 expert observations.This work led to the production of new maps of debris flow triggering and propagation, already integrated on a service platform (RHYTMME project, Irstea and Météo-France). They can be superimposed on maps of precipitation hazard during intense events in order to identify the reaches susceptible to debris flow activity.
332

Caracterização geoambiental da bacia hidrográfica do Rio das Antas utilizando ferramentas de geoprocessamento / Characterization geoenvironmental of the watershed of the antas river using tools of geoprocessing

Borghetti, Alex 18 December 2006 (has links)
Made available in DSpace on 2017-05-12T14:46:53Z (GMT). No. of bitstreams: 1 Alex Borghetti.pdf: 8925497 bytes, checksum: c9f05ef8ac030f884a127e4bfe980c76 (MD5) Previous issue date: 2006-12-18 / The main goal of this paper it is to characterize the geoenvironmental of the hydrographic basin in Antas River, which is located in the city of Cascavel PR. The total area it is 134.53 km², divided in 21% of urban area and 79% of rural area. During the collection, manipulation and presentation of all the data related to the usage of soil, geomorphology and the conservation of the water s bodies had been used: cartographic and geographic information system (GIS) and images of satellite with high space resolution. All the way the soil was capture from the satellite image the rural area it was captured in the internet and georeferenced through control points traced by GPS. All the outcome was produced by thematic maps where was possible analyze the quantity and visualized the detail. Related to geomorphology, the basin showed 74.2% of the area insert in level I and II (convex top and soft slope). Considering the used of soil in the urban area 73.0%, is being occupied for related urbanization level in the rural area, the agriculture with 80.3%. The verification of APP (Area of Preservation Permanent) the rural area has only 55.6% of the area was formed for gallery forest, the urban perimeter percent was reduce 25.5%. The shortage ambient confirmed the quantities of the legal reserve that have only 34.8% of the area was occupied for vegetation. Using those perimeters it was possible to evaluate the physic space of the basin hydrographic, helping the process of hydrous assets. / Este trabalho objetivou a caracterização geoambiental da bacia hidrográfica do Rio das Antas, localizada no município de Cascavel PR, a qual possui uma área de 134,53 km², dividida entre área urbana (21%) e rural (79%). Na coleta, manipulação e representação dos dados referentes ao uso do solo, geomorfologia e preservação dos corpos d água foram utilizados: cartografia digital, sistemas de informações geográficas (SIG) e imagens de satélite de alta resolução espacial. As classes de uso do solo foram vetorizadas sobre a imagem de satélite que, na área rural foi capturada na internet e georreferenciada por meio de pontos de controle rastreados por GPS. Como resultados foram produzidos mapas temáticos nos quais a quantificação e a visualização das características puderam ser analisadas. Em relação à geomorfologia, a bacia apresentou 74,2% da área inserida nas classes I e II (topos convexos e encostas suaves). Considerando o uso do solo na parte urbana, 73,0%, da área está ocupada por classes relacionadas à urbanização. Na parte rural, a classe agricultura é predominante: 80,3%. Na verificação da Área de Preservação Permanente - APP, a parcela rural possui somente 55,6% da área formada por mata ciliar, e no perímetro urbano o percentual é reduzido para 24,5%. A falta de consciência ambiental é confirmada pela quantificação da reserva legal, que possui somente 34,8% da respectiva área ocupada pelas classes de vegetação. Com base nestes parâmetros, foi possível analisar o espaço físico da bacia hidrográfica, contribuindo para o processo de gestão dos recursos hídricos.
333

街道特徵與地標位置識別之研究 / Content-based map localization using street map with landmarks

李澤毅, Li, Ze Yi Unknown Date (has links)
隨著GIS的發展,地圖定位成為空間查詢中極為普遍的行為。一般地圖定位大多透過地址來進行,但是在缺乏地址的情況之下,進行地圖上之定位變成極為困難之事。 本論文嘗試對手繪地圖在真實地圖上進行定位,我們提出了一套機制,使用者可以隨意地以手繪方式繪製街道圖與地標,透過我們提出的方法,即可自動地在真實的地圖上進行定位。 論文中,我們使用相鄰街廓中之地標配置與相鄰之交叉路口之地標配置等變數組成的表示法來描述地圖。我們將手繪地圖與真實地圖轉換成這些表示法,並透過字串編輯距離、圖同構等關係來比較手繪地圖與真實地圖之相似度,從而對手繪地圖進行定位。 實作中,我們挑選了幾處真實場景在台北市地圖中進行比對並觀察其結果。系統採用之地標包括政府機構(如派出所、消防隊、區公所等)、學校、醫院等資料。在實驗中,應用這套表示法可成功的定位出使用者所輸入之各場景所在位置。另外,透過控制相似度門檻值,我們可以調整辨識之精確度,不至於錯失可能之定位結果。 / As the widely spread of the GIS applications, map localization becomes one of the most important features in the spatial information retrieval. Normally, map localization is done through street addresses. Without this information, map localization becomes very difficult. In this research, we are trying to do map localization using hand drawing maps. We proposed a mechanism that can localize the user's drawing map in the reference map automatically. Our approaches use the landmark configurations of the adjacent street blocks as well as the landmark configurations of the adjacent street intersections as the descriptors in representing a map. The user's hand drawn maps and the reference maps are converted into these representations. The string editing distances and graph isomorphism are used in determining the similarities between the hand drawn map and the reference map. The map localization can be done by comparing these similarities. We used various real scenes in Taipei City to verify our systems. The landmarks we used including police offices, fire stations, county offices, schools and hospitals, etc. The experimental results shown that our system can localize the user's input successfully. Moreover, by controlling thresholds in similarity analysis, we can adjust the system's accuracy that reduces possibility of miss localizations.
334

Flood Impact Analysis using GIS : A case study for Lake Roxen and Lake Glan - Sweden

Vaghani, Vimalkumar January 2005 (has links)
<p>Floods are common natural disaster occurring in most parts of the world. This results in damage to human life and deterioration of environment. There have been immense uses of technology to mitigate measures of flood disaster i.e. structurally and non-structurally. Undoubtedly, structural measures are very expensive and time consuming which involves physical work like construction of dams, reservoirs, bridges, channel improvement, river diversion and other embankments to keep floods away from people. Whereas non-structural measures is concerned with planning like flood forecasting and warning, flood plain zoning, relief and rehabilitation for reducing the risk of flood damage to keep people away from floods. Thus, non-structural measures involve analysis, planning providing spatial information on maps with high accuracy in less time. Non-structural measures can help decision maker to plan an effective emergency response towards flood disaster. A one of the good way to plan non-structural measures is to analyze impact of flood in the flood prone areas. The thesis tries to analyze impact of flood on environment along the demarcated flood prone areas of Lake Roxen and Lake Glan in Östergötland County, Sweden. The thesis also proposes how to use current flood information during flood emergency utilizing geographical information system. This provides spatial information for area in the flood zone for assessment regarding flood vulnerability.</p><p>Using map overlay analysis in GIS software (ArcGIS); flood prone areas and topographic data along Lake Roxen and Lake Glan were digitized from PDF maps. Thus, the thesis work is an effort to analyze impact of flood when areas along Lake Roxen and Lake Glan are flooded. ESRI® GIS software Arc Map 9 and Arc View 3.3 is used for data preparation, integrating, analyzing, and spatial data with attribute table information. Finally, to show GIS can be an effective tool for development of flood emergency system as a part of disaster preparedness by the decision makers.</p>
335

Kan inte alla samma språk? : Möjligheten till ett gemensamt GGIS på mekaniserade förband? / Can’t all talk the same language? : Possibility to a common GIS at mechanized units?

Sandberg, Jonas January 2010 (has links)
<p>Försvarsmakten har under de senaste åren gått igenom radikala förändringar, som fortfarande inte är klara. Samtidigt som fokus ligger på personalförsörjning samt annat så går den teknologiska utvecklingen framåt. Jag vill med denna uppsats belysa vad ett gemensamt geografiskt informationssystem skulle kunna innebära för chefer på en lägre nivå inom mekaniserade bataljoner. Med denna uppsatts vill jag skapa förståelse utav gemensamma geografiska informationssystem och vilka möjligheter de skulle kunna bidra med. I uppsatsen tar jag reda på om systemen skulle kunna underlätta för chefer i sitt ledarskap på slagfälten, likväl vilka effekter det stridstekniskt skulle kunna bidra med. Jag tar också reda på om Försvarsmakten med dagens materiell och teknologi kan uppbringa ett sådant system. Slutsatsen som dras är att Försvarsmakten inte med dagens materiell kan uppbringa ett sådant system, materielen är föråldrad och den främsta begränsningen är dataöverförningskapacitet. Andra slutsatser är att system som dessa underlättar för chefer ur flertalet perspektiv. Främst så skulle systemen kunna bidraga till högre stridseffektivitet och underlätta för så kallade mixade förband.</p> / <p>The Swedish Armed forces have under the past years gone through some radical changes and some of them are still going on. As focus is set on manpower, the technologic development moves forward. I want to highlight what a common graphical information system could mean to commanders on lower command level at mechanized units. With this essay I want to create an understanding of common geographical information systems and what opportunities it could help with. In the essay I will find out if the systems could favor commanders in their leadership on the battlefield, as well which effects it could have on battle tactics. I also find out if the Swedish Armed forces with today’s equipment could procure such a system. Conclusions of the essay is that the Swedish Armed forces cant with today’s equipment procure such an system, because of the equipments obsolete status and the prominent restriction is data transfer rate. Other conclusions are that systems like these favor commanders in several perspectives. Most prominent, could system like these contribute to higher battle efficiency and favor for mechanized- mixed unit types.</p>
336

Kan inte alla samma språk? : Möjligheten till ett gemensamt GGIS på mekaniserade förband? / Can’t all talk the same language? : Possibility to a common GIS at mechanized units?

Sandberg, Jonas January 2010 (has links)
Försvarsmakten har under de senaste åren gått igenom radikala förändringar, som fortfarande inte är klara. Samtidigt som fokus ligger på personalförsörjning samt annat så går den teknologiska utvecklingen framåt. Jag vill med denna uppsats belysa vad ett gemensamt geografiskt informationssystem skulle kunna innebära för chefer på en lägre nivå inom mekaniserade bataljoner. Med denna uppsatts vill jag skapa förståelse utav gemensamma geografiska informationssystem och vilka möjligheter de skulle kunna bidra med. I uppsatsen tar jag reda på om systemen skulle kunna underlätta för chefer i sitt ledarskap på slagfälten, likväl vilka effekter det stridstekniskt skulle kunna bidra med. Jag tar också reda på om Försvarsmakten med dagens materiell och teknologi kan uppbringa ett sådant system. Slutsatsen som dras är att Försvarsmakten inte med dagens materiell kan uppbringa ett sådant system, materielen är föråldrad och den främsta begränsningen är dataöverförningskapacitet. Andra slutsatser är att system som dessa underlättar för chefer ur flertalet perspektiv. Främst så skulle systemen kunna bidraga till högre stridseffektivitet och underlätta för så kallade mixade förband. / The Swedish Armed forces have under the past years gone through some radical changes and some of them are still going on. As focus is set on manpower, the technologic development moves forward. I want to highlight what a common graphical information system could mean to commanders on lower command level at mechanized units. With this essay I want to create an understanding of common geographical information systems and what opportunities it could help with. In the essay I will find out if the systems could favor commanders in their leadership on the battlefield, as well which effects it could have on battle tactics. I also find out if the Swedish Armed forces with today’s equipment could procure such a system. Conclusions of the essay is that the Swedish Armed forces cant with today’s equipment procure such an system, because of the equipments obsolete status and the prominent restriction is data transfer rate. Other conclusions are that systems like these favor commanders in several perspectives. Most prominent, could system like these contribute to higher battle efficiency and favor for mechanized- mixed unit types.
337

Flux Measurements of Volatile Organic Compounds from an Urban Tower Platform

Park, Chang Hyoun 2010 May 1900 (has links)
A tall tower flux measurement setup was established in metropolitan Houston, Texas, to measure trace gas fluxes from both anthropogenic and biogenic emission sources in the urban surface layer. We describe a new relaxed eddy accumulation system combined with a dual-channel gas chromatography - flame ionization detection used for volatile organic compound (VOC) flux measurements in the urban area, focusing on the results of selected anthropogenic VOCs, including benzene, toluene, ethylbenzene and xylenes (BTEX), and biogenic VOCs including isoprene and its oxidation products, methacrolein (MACR) and methyl vinyl ketone (MVK). We present diurnal variations of concentrations and fluxes of BTEX, and isoprene and its oxidation products during summer time (May 22 - July 22, 2008) and winter time (January 1 - February 28). The measured BTEX values exhibited diurnal cycles with a morning peak during weekdays related to rush-hour traffic and additional workday daytime flux maxima for toluene and xylenes in summer time. However, in winter time there was no additional workday daytime peaks due mainly to the different flux footprints between the two seasons. A comparison with different EPA National Emission Inventories (NEI) with our summer time flux data suggests potential underestimates in the NEI by a factor of 3 to 5. The mixing ratios and fluxes of isoprene, MACR and MVK were measured during the same time period in summer 2008. The presented results show that the isoprene was affected by both tail-pipe emission sources during the morning rush hours and biogenic emission sources in daytime. The observed daytime mixing ratios of isoprene were much lower than over forested areas, caused by a comparatively low density of isoprene emitters in the tower's footprint area. The average daytime isoprene flux agreed well with emission rates predicted by a temperature and light only emission model (Guenther et al., 1993). Our investigation of isoprene's oxidation products MACR and MVK showed that both anthropogenic and biogenic emission sources exist for MACR, while MVK was strongly dominated by a biogenic source, likely the isoprene oxidation between the emission and sampling points.
338

Assessing processes of long-term land cover change and modelling their effects on tropical forest biodiversity patterns – a remote sensing and GIS-based approach for three landscapes in East Africa

Lung, Tobias 24 November 2010 (has links) (PDF)
The work describes the processing and analysis of remote sensing time series data for a comparative assessment of changes in different tropical rainforest areas in East Africa. In order to assess the effects of the derived changes in land cover and forest fragmentation, the study made use of spatially explicit modelling approaches within a geographical information system (GIS) to extrapolate sets of biological field findings in space and time. The analysis and modelling results were visualised aiming to consider the requirements of three different user groups. In order to evaluate measures of forest conservation and to derive recommendations for an effective forest management, quantitative landscape-scale assessments of land cover changes and their influence on forest biodiversity patterns are needed. However, few remote sensing studies have accounted for all of the following aspects at the same time: (i) a dense temporal sequence of land cover change/forest fragmentation information, (ii) the coverage of several decades, (iii) the distinction between multiple forest formations and (iv) direct comparisons of different case studies. In regards to linkages of remote sensing with biological field data, no attempts are known that use time series data for quantitative statements of long-term landscape-scale biodiversity changes. The work studies three officially protected forest areas in Eastern Africa: the Kakamega-Nandi forests in western Kenya (focus area) and Mabira Forest in south-eastern Uganda as well as Budongo Forest in western Uganda (for comparison purposes). Landsat imagery of in total eight or seven dates in regular intervals from 1972/73 to 2003 was used. Making use of supervised multispectral image classification procedures, in total, 12 land cover classes (six forest formations) were distinguished for the Kakamega-Nandi forests and for Budongo Forest while for Mabira Forest ten classes could be realised. An accuracy assessment via error matrices revealed overall classification accuracies between 81% and 85%. The Kakamega-Nandi forests show a continuous decrease between 1972/73 and 2001 of 31%, Mabira Forest experienced an abrupt loss of 24% in the late 1970s/early 1980s, while Budongo Forest shows a relatively stable forest cover extent. An assessment of the spatial patterns of forest losses revealed congruence with areas of high population density while a spatially explicit forest fragmentation index indicates a strong correlation of forest fragmentation with forest management regime and forest accessibility by roads. For the Kenyan focus area, three sets of biological field abundance data on keystone species/groups were used for a quantitative assessment of the influence of long-term changes in tropical forests on landscape-scale biodiversity patterns. For this purpose, the time series was extended with another three land cover data sets derived from aerial photography (1965/67, 1948/(52)) and old topographic maps (1912/13). To predict the spatio-temporal distribution of the army ant Dorylus wilverthi and of ant-following birds, GIS operators (i.e. focal and local functions) and statistical tests (i.e. OLS or SAR regression models) were combined into a spatial modelling procedure. Abundance data on three guilds of birds differing in forest dependency were directly extrapolated to five forest cover classes as distinguished in the time series. The results predict declines in species abundances of 56% for D. wilverthi, of 58% for ant-following birds and an overall loss of 47% for the bird habitat guilds, which in all three cases greatly exceed the rate of forest loss (31%). Additional extrapolations on scenarios of deforestation and reforestation confirmed the negative ecological consequences of splitting-up contiguous forest areas but also showed the potential of mixed indigenous forest plantings. The visualisation of the analysis and modelling results produced a mixture of different outcomes. Map series and a matrix of maps both showing species distributions aim to address scientists and decision makers. The results of the land cover change analysis were synthesised in a map of land cover development types for each study area, respectively. These maps are designed mainly for scientists. Additional maps of change, limited to a single class of forest cover and to three dates were generated to ensure an easy-to-grasp communication of the major forest changes to decision makers. Additionally, an easy-to-handle visualisation tool to be used by scientists, decision makers and local people was developed. For the future, an extension of this study towards a more complete assessment including more species/groups and also ecosystem functions and services would be desirable. Combining a framework for land cover simulation with a framework for running empirical extrapolation models in an automated manner could ideally result in a GIS-based, integrated forest ecosystem assessment tool to be used as regional spatial decision support system. / Die Arbeit beschreibt die Prozessierung und Analyse von Fernerkundungs-Zeitreihendaten für eine vergleichende Abschätzung von Veränderungen verschiedener tropischer Waldökosysteme Ostafrikas. Um Effekte der Veränderungen bzgl. Landbedeckung und Waldfragmentierung auf Biodiversitätsmuster abzuschätzen, wurden verschiedene räumlich explizite Modellierungssätze innerhalb eines geographischen Informationssystems (GIS) zur räumlichen und zeitlichen Extrapolation biologischer Felderhebungsdaten benutzt. Die Visualisierung der Analyse- und Modellierungsergebnisse erfolgte unter Berücksichtigung der Bedürfnisse von drei verschiedenen Nutzergruppen. Um Waldschutzmaßnahmen zu evaluieren und Empfehlungen für ein effektives Waldmanagement abzuleiten, sind quantitative Abschätzungen von Landbedeckungsveränderungen sowie von deren Einfluss auf tropische Waldbiodiversitätsmuster nötig. Wenige fernerkundungsbasierte Studien haben jedoch bislang alle der folgenden Faktoren berücksichtigt: (i) Informationen zu Veränderungen von Landbedeckung und Waldfragmentierung in dichter zeitlicher Sequenz, (ii) die Abdeckung mehrerer Jahrzehnte, (iii) die Unterscheidung zwischen mehreren Waldformationen, und (iv) direkte Vergleiche von unterschiedlichen Fallstudien. Hinsichtlich Verknüpfungen von Fernerkundung mit biologischen Felddaten sind bisher keine Studien bekannt, die Zeitreihendaten für quantitative Aussagen zu Langzeitveränderungen von Biodiversität auf Landschaftsebene verwenden. Die Arbeit untersucht drei offiziell geschützte Gebiete: die Kakamega-Nandi forests in Westkenia (Hauptuntersuchungsgebiet) sowie Mabira Forest in Südost-Uganda und Budongo Forest in West-Uganda (zu Vergleichszwecken). Es wurden Landsat-Daten für insgesamt acht bzw. sieben Zeitpunkte zwischen 1972/73 und 2003 in ungefähr gleichen Abständen erworben. Mit Hilfe von überwachten, multispektralen Klassifizierungsverfahren wurden für die Kakamega-Nandi forests und Budongo Forest jeweils 12 Landbedeckungsklassen (sechs Waldformationen) und für Mabira Forest zehn Klassen unterschieden. Eine Genauigkeitsprüfung mit Hilfe von Fehlermatrizen ergab Gesamtklassifizierungsgenauigkeiten zwischen 81% und 85%. Die Kakamega-Nandi forests sind durch eine kontinuierliche Waldabnahme von 31% zwischen 1972/73 und 2001 gekennzeichnet, Mabira Forest zeigt einen abrupten Waldverlust von 24% in den späten 1970ern/frühen 1980ern, während die Ergebnisse für Budongo Forest eine relativ stabile Waldbedeckung ausweisen. Während eine Abschätzung der räumlichen Muster von Waldverlusten eine hohe Deckungsgleichheit mit Gebieten hoher Bevölkerungsdichte ergab, deutet die Anwendung eines räumlich expliziten Waldfragmentierungsindexes auf eine starke Korrelation von Waldfragmentierung mit der Art von Waldmanagement sowie mit der Erreichbarkeit von Wald über Straßen hin. Um den Einfluss von Langzeit-Landbedeckungsveränderungen auf Biodiversitätsmuster auf Landschaftsebene für das kenianische Hauptuntersuchungsgebiet quantitativ abzuschätzen wurden drei Datensätze mit biologischen Felderhebungen zur Abundanz von Schlüsselarten/-gruppen verwendet. Zu diesem Zweck wurde die Zeitreihe zunächst um drei weitere Landbedeckungs-Datensätze ergänzt, die aus Luftbildern (1965/67, 1948/(52)) bzw. alten topographischen Karten (1912/13) gewonnen wurden. Zur Vorhersage der raum-zeitlichen Verteilung der Treiberameise Dorylus wilverthi wurden GIS-Operatoren und statistische Tests (OLS bzw. SAR Regressionsmodelle) in einem räumlichen Modellierungsablauf kombiniert. Abundanzdaten von drei sich hinsichtlich ihrer Abhängigkeit von Wald unterscheidenden Vogelgilden wurden direkt auf fünf Waldbedeckungsklassen hochgerechnet, die in der Zeitreihe unterschieden werden konnten. Die Ergebnisse prognostizieren Abundanzabnahmen von 56% für D. wilverthi, von 58% für Ameisen-folgende Vögel und einen Gesamtverlust von 47% für die Vogelgilden, was in allen drei Fällen eine deutliche Überschreitung der Waldverlustrate von 31% darstellt. Zusätzliche Extrapolationen basierend auf Szenarien bestätigten die negativen ökologischen Konsequenzen der Zerteilung zusammenhängender Waldflächen bzw. zeigten andererseits das Potential von Aufforstungen mit einheimischen Arten auf. Die Visualisierung der Analyse- bzw. Modellierungsergebnisse führte zu unterschiedlichen Darstellungen: mit einer Reihe von nebeneinander positionierten Einzelkarten sowie einer Matrix von Einzelkarten, die jeweils Artenverteilungen zeigen, sollen Wissenschaftler und Entscheidungsträger angesprochen werden. Aus den Ergebnissen der Landbedeckungsanalyse für die drei Untersuchungsgebiete wurden Landbedeckungsveränderungstypen generiert und jeweils in einer synthetischen Karte dargestellt, die hauptsächlich für Wissenschaftler gedacht sind. Um die wesentlichen Waldveränderungen auch auf einfache Weise zu den Entscheidungsträgern zu kommunizieren, wurden zusätzliche Karten erstellt, die nur eine aggregierte Klasse „Waldbedeckung“ zeigen und jeweils auf drei Zeitschritte der Zeitreihen begrenzt sind. Zusätzlich wurde ein leicht zu bedienendes Visualisierungstool entwickelt, das für Wissenschaftler, Entscheidungsträger und die lokale Bevölkerung gedacht ist. Für die Zukunft wäre eine umfassendere Abschätzung unter Berücksichtigung zusätzlicher Arten/-gruppen sowie auch Ökosystemfunktionen und –dienstleistungen wünschenswert. Die Verknüpfung einer Applikation zur Landbedeckungsmodellierung mit einer Applikation zur Ausführung von empirischen Extrapolationsmodellen (in stärkerem Maße automatisiert als in dieser Arbeit) könnte im Idealfall in ein GIS-basiertes Tool zur integrativen Bewertung von Waldökosystemen münden, das dann als räumliches Entscheidungsunterstützungssystem verwendet werden könnte.
339

Ανάπλαση του φυσικού περιβάλλοντος της παράκτιας ζώνης της ελληνιστικής Αλεξάνδρειας (Αιγύπτου), με τη χρήση θαλάσσιων γεωφυσικών μεθόδων και γεωγραφικών συστημάτων πληροφοριών / Alexandrea ad Aegyptum : palaeoenvironmental reconstruction of the coastal zone, using geophysical techniques and Geographical Information Systems (GIS)

Χάλαρη, Αθηνά 01 September 2009 (has links)
Η παρούσα διδακτορική διατριβή μελετά την παράκτια ζώνη, της Αλεξάνδρειας (Αιγύπτου) με σκοπό: (1) την ανάπλαση του παράκτιου παλαιοπεριβάλλοντος στο οποίο αναπτύχθηκε η Ελληνιστική Αλεξάνδρεια και πώς αυτό επηρέασε στην ίδρυση και στην εξέλιξη της πόλης, (2) τον εντοπισμό ναυαγίων, καταβυθισμένων λιμενικών εγκαταστάσεων και άλλων μαρτυριών ανθρώπινης δραστηριότητας. Για την επίτευξη των παραπάνω στόχων xρησιμοποιήθηκαν εξειδικευμένες θαλάσσιες γεωφυσικές τεχνολογίες, όπως ηχοβολιστής πλευρικές σάρωσης, τομογράφος υποδομής πυθμένα, απλό και διαφορικό GPS. Η ανάλυση και επεξεργασία των συλλεγέντων δεδομέμων πραγματοποιήθηκε με τη βοήθεια των υπολογιστικών πακέτων Matlab και ArcGIS. Δημιουργήθηκαν πρωτότυπα και εύχρηστα μεθοδολογικά σχήματα (PalaeogAn και TargAn), με τη βοήθεια σύγχρονων μεθόδων επεξεργασίας και ανάλυσης εικόνας, με σκοπό την επεξεργασία των αναλογικών γεωφυσικών καταγραφών, σε ένα αυτοματοποιημένο ψηφιακό περιβάλλον. Η ανάλυση των γεωφυσικών καταγραφών έδειξε την ύπαρξη μίας kurkar δομής σχήματος Τ παρόμοιας σε σχήμα, σύσταση και προσανατολισμό με το δομικό σύστημα νήσος Φάρος-Επταστάδιο-Λιμένες της Αλεξάνδρειας, μετατοπισμένη προς τα ΒΑ. Η μελέτη των μεταβολών της στάθμης της θάλασσας και η ανάλυση των τομογραφιών, έδειξε ότι η παράκτια ζώνη της Αλεξάνδρειας διαμορφώνεται από μία σειρά επάλληλων παλαιοακτών, σε βάθη νερού 16, 14, 12, 10, 8 m, οι οποίες αντιστοιχούν στην ακτογραμμή της περιοχής το 3300π.Χ (βασίλειο Harpoon), 2700π.Χ, 2000π.Χ, 1400π.Χ (οικισμός Ραχώτιδας), και 300π.Χ (Πτολεμαϊκή Αλεξάνδρεια) αντίστοιχα. Η δομή Τ ήταν πάνω από την επιφάνεια της θάλασσας και διαμόρφωνε ασφαλές αγκυροβόλιο (3300-2000π.Χ), ενώ αργότερα βυθίστηκε (2000-300π.Χ) αρχικά στα -2m (1400π.Χ) και στη συνέχεια στα -4m βάθος (300π.Χ), ενεργώντας ως φυσικός κυματοθραύστης που προστάτευε την ακτή από τη διάβρωση και τη θαλασσοταραχή. Επίσης φαίνεται ότι η είσοδος του Ανατολικού Λιμένα στα Πτολεμαϊκά χρόνια ήταν πολύ στενή (600m), στα ΒΑ της Άκρας Λοχιάδος και στο εσωτερικό του Ανατολικού Λιμένα εκείνη την εποχή υπήρχαν βραχονησίδες, το 92% της Άκρας Λοχιάδος είναι σήμερα καταβυθισμένο. Τέλος επιτεύχθηκε α) ο εντοπισμός ενός αρχαίου ναυαγίου, δύο περιοχών με έρματα αρχαίων πλοίων, δύο αρχαίων προβόλων, δύο σχηματισμών που πιθανώς αποτελούν αρχαία ναύδετα, β) ο εντοπισμός 57 στόχων, η αρχαιολογική σημασία των οποίων αξιολογήθηκε με τη βοήθεια του TargAn και πολυδιάστατων στατιστικών μεθόδων γ) η υπόδειξη νέων περιοχών αρχαιολογικού ενδιαφέροντος. / The aim of this PhD is twofold: (a) to reconstruct the palaeoenvironmental setting where Hellenistic Alexandria was developed, (b) to detect the presence of any prehistorical and historical shipwrecks and evidence of human activity. In order to accomplish the above a geophysical survey was carried out, using a sidescan sonar and a subbottom profiler system, while the positioning was provided by a GPS and DGPS. The geophysical data were analyzed using a Matlab and an ArcGIS software. New, user-friendly methodological schemes, referred to as PalaeogAn και TargAn, were developed using image analysis techniques, in order to analyse analogue geophysical data in a digital environment. The geophysical data analysis shows the presence of a Τ-shape kurkar ridge, which stands at a minimum water depth of 11m below the seasurface at the north end of the Eastern Harbour of Alexandria. This kurkar formation is almost identical with that of the Pharos island–Heptastadion-Alexandria Harbours. Sea level changes and geophysical data analysis suggest that Alexandria’s coastal zone is characterized by a series of parallel submerged palaeoshorelines, at water depths of 16, 14, 12, 10 and 8 m, which represent the coastlines of 3300 BC (kingdom of Harpoon), 2700 BC, 2000 BC, 1400 BC (ancient Rachotis), and 300 BC (Ptolemaic Alexandria) respectively. The Τ-shape structure between 3300-2000BC was above msl creating a safe anchorage for ancient ships. In 1400 BC and 300 BC it was 2m and 4m under msl respectively, acting as a natural breakwater and protecting the coast from wave action. During the Hellenistic times (300 BC) the Eastern Harbour entrance was much smaller (600m) than today. At the northeastern end of Cape Lochias and in the inner Eastern Harbour dangerous shoals and reefs were scattered. Cape Lochias was much larger than it is today as the most of it (92%) is at present submerged. The insonification revealed (a) the existence of an ancient shipwreck, two areas with ship ballast, two structures which might have been used as buoys, two structures that were propably used as moles, (b) the presence of 57 acoustic anomalies, which were analyzed using the TargAn and multivariate statistical methods, (c) new areas of archaeological importance to be surrveyed in the near future. The results of the statistical analysis classified the acoustic anomalies into groups showing their archaeological validity.
340

Contribució al coneixement de variables geoambientals en l'àmbit de la Costa Brava (Girona)

Geis Nielsen, Christian 28 June 2005 (has links)
La tesi doctoral desenvolupada, emmarcada dins del camp de les Ciències Ambientals, aplica la Geologia Ambiental orientada al coneixement dels processos i recursos geològics de cara a la planificació i a l'ordenació del territori. Com a zona d'estudi s'ha seleccionat la Costa Brava meridional, concretament tota l'àrea litoral compresa per les conques hidrogràfiques de l'Aubi, riera de Calonge, Ridaura, riera de Tossa i riera de Lloret (75 km de línia de costa i una extensió de 291 km2).Aquest treball, amb l'aptitud integradora dels conceptes i mètodes propis de les Ciències Geològiques i Ambientals, s'ha proposat com a objectius globals l'anàlisi de la qualitat i del comportament físic i químic dels materials terrestres en front les accions humanes i de la seva utilització com a recursos; l'estudi dels processos naturals i de la influència que puguin tenir sobre l'home o bé els efectes que aquest pot causar sobre aquells, i per últim, com a derivació dels anteriors, el disseny i aplicació d'instruments de tipus preventiu en la gestió del territori; és a dir, la planificació dels usos del territori.Amb la filosofia de recerca basada en que els factor geològics són uns elements d'ajuda per a la visió integral d'un territori, s'han estudiat diferents variables geoambientals procurant traduir el coneixement del medi en informació apta per a la presa de decisions sobre l'ús i preservació d'aquest àmbit litoral. Els Sistemes d'Informació Geogràfica (SIG) han estat clau per a la visió sistèmica del territori, per a la integració de les diferents variables geoambientals, així com per a la producció cartogràfica temàtica i final. Pel que fa als processos geològics, lligats a la dinàmica fluviotorrencial, s'han cartografiat les principals àrees d'actuació així com analitzat els factors que inicien, afavoreixen o magnifiquen la seva ocurrència. S'han estudiat les accions denudatives, els processos de transport-sedimentació i amb l'estudi integrat d'aquests processos i formes resultants s'han identificat unitats territorials caracteritzades per un comportament geomòrfic uniforme.En quant a l'anàlisi dels recursos geològics s'ha aprofundit en el coneixement dels recursos hídrics subterranis, les roques industrials i els georecursos litorals. Pel que fa als primers s'ha centrat en la delimitació de les principals unitats i subunitats aqüíferes, així com en acotar les geometries i principals característiques hidràuliques. Pel que fa als àrids i roques de construcció l'objectiu fonamental ha estat la delimitació cartogràfica d'aquells materials que per les seves propietats fisicoquímiques són potencialment aptes per als usos indicats. Finalment s'ha fet una recerca orientada a l'estudi de factors que limiten o condicionen el potencial geoturístic d'aquesta àrea litoral, concretament en els penya-segats i les platges.Les principals aportacions d'aquesta tesi doctoral es poden emmarcar en l'àmbit regional i fenomenològic, aspectes clau en la gestió i planificació territorial. Pel que fa al primer, destaquem l'aportació de dades geoambientals a nivell cartogràfic en relació a variables litoestructurals, de processos dinàmics com de recursos geològics. Des del punt de vista de l'àmbit fenomenològic destaquem la interacció de les variables estudiades a nivell de conca hidrogràfica, com són, entre d'altres, les relacions existents entre les diferents formacions aqüíferes; la possible participació de les aigües subterrànies en la resposta hidrològica del sistema fluviotorrencial, o la problemàtica derivada de l'antropització de la sorra de la platja com a conseqüència d'abocaments de terres i residus inerts als marges de les rieres. / La tesis doctoral desarrollada, enmarcada dentro del campo de las Ciencias Ambientales, aplica la Geología Ambiental orientada al conocimiento de los procesos y recursos geológicos para la planificación y ordenación del territorio. Como zona de estudio se ha seleccionado la Costa Brava meridional, concretamente toda el área litoral comprendida por las cuencas hidrográficas de la Aubi, riera de Calonge, Ridaura, riera de Tossa y riera de Lloret (75 km de línea de costa y una extensión de 291 km2).Este trabajo, con la aptitud integradora de los conceptos y métodos propios de las Ciencias Geológicas y Ambientales, se ha propuesto como objetivos globales el análisis de la calidad y del comportamiento físico y químico de los materiales terrestres en frente las acciones humanas y de su utilización como recursos; el estudio de los procesos naturales y de la influencia que puedan tener sobre el hombre o bien los efectos que este puede causar sobre aquellos, y por último, como derivación de los anteriores, el diseño y aplicación de instrumentos de tipo preventivo en la gestión del territorio; es decir, la planificación de los usos del territorio. Con la filosofía de investigación basada en que los factores geológicos son unos elementos de ayuda para la visión integral de un territorio, se han estudiado diferentes variables geoambientales procurando traducir el conocimiento del medio en información apta para la toma de decisiones sobre el uso y preservación de este ámbito litoral. Los Sistemas de Información Geográfica (SIG) han sido clave para la visión sistémica del territorio, para la integración de las diferentes variables geoambientales, así como para la producción cartográfica temática y final.Con respecto a los procesos geológicos, relacionados con la dinámica fluviotorrencial, se han cartografiado las principales áreas de actuación así como analizado los factores que inician, favorecen o magnifican su ocurrencia. Se han estudiado las acciones denudativas, los procesos de transporte-sedimentación y con el estudio integrado de estos procesos y formas resultantes se han identificado unidades territoriales caracterizadas por un comportamiento geomórfico uniforme.En cuanto al análisis de los recursos geológicos se ha profundizado en el conocimiento de los recursos hídricos subterráneos, las rocas industriales y los georecursos litorales. Con respecto a los primeros nos hemos centrado en la delimitación de las principales unidades y subunidades acuíferas, así como en acotar las geometrías y principales características hidráulicas. Con respecto a los áridos y rocas de construcción el objetivo fundamental ha sido la delimitación cartográfica de aquellos materiales que por sus propiedades fisicoquímicas son potencialmente aptas para los usos indicados. Finalmente se ha hecho un estudio orientado a los factores que limitan o condicionan el potencial geoturístico de esta área litoral, concretamente en los acantilados y las playas.Las principales aportaciones de esta tesis doctoral se pueden enmarcar en el ámbito regional y fenomenológico, aspectos clave en la gestión y planificación territorial. Con respecto al primero, destacamos la aportación de datos geoambientales a nivel cartográfico de variables litoestructurales, de procesos dinámicos i de recursos geológicos. Desde el punto de vista del ámbito fenomenológico destacamos la interacción de las variables estudiadas a nivel de cuenca hidrográfica, como son, entre otras, las relaciones existentes entre las diferentes formaciones acuíferas; la posible participación de las aguas subterráneas en la respuesta hidrológica del sistema fluviotorrencial, o la problemática derivada de la antropización de la arena de la playa como consecuencia de vertidos de tierras y residuos inertes a los márgenes de las rieras. / This thesis developed is framed within the scope of the Environmental Sciences. Environmental Geology is applied to understand the geological processes and resources that take place in the area, thus enhancing the management of the territory. All the littoral area within the hydrographical basins of the Aubi, riera de Calonge, Ridaura, riera de Tossa and riera de Lloret (75 km of coast line and an extension of 291 sq.km), a good part of the southern Costa Brava, has been selected as the study zone.This work, with its ability to integrate the concepts and methods of the Environmental and Geological Sciences, has three main objectives: the analysis of the quality and the physical and chemical behaviour of the terrestrial materials in front of human actions and its utilization as resources; the study of the natural processes and the influences that they have on the antropic activity, or the effects that this can cause on those; and as a derivation of the previous objectives, the design and application of preventive instruments for the management of the territory, that is to say, the planning of the uses of the territory.Considering geological factors as helping elements to achieve an integral vision of a territory, different geoenvironmental variables have been studied. It has been tried to translate the acquired knowledge into information which could be used by the planners of this coastal environment for their decision making process. The Geographical Information Systems (GIS) have been a key factor to keep a systemic vision of the territory. They have also made possible the integration of the different geoenvironmental variables, as well as the cartographic production.With regard to the geological processes related to the fluviotorrencial dynamics, the main areas of their action have been mapped. The factors that initiate, favor or increase their occurrence have been analysed as well. The denudation actions, processes of transportation and sedimentation have also been studied. With the integrated study of all these processes and resultant forms, several territorial units characterized by a uniform geomorphic behaviour have been identified.With the analysis of the geological resources, we have contributed to the knowledge of the subterranean water resources, the industrial rocks and the coastal georesources. With regard to the first item we have put most of our efforts in the delimitation of the main aquifer units and subunits, as well as in the study of their geometries and their main hydraulic characteristics. With regard to the mining activity, the fundamental objective has been the cartographic delimitation of those materials which, by their physiochemical properties, are potentially apt for the indicated uses. Finally a study oriented to the factors that limit or condition the geotouristic potential of this littoral area has been done, specifically at the cliffs and in the beaches.The main contributions of this thesis can be framed in regional and phenomenological fields, both of which are key aspects in management and territorial planning. With respect to the regional ones, we would like to emphasize the contribution of geoenvironmental cartographic data related to litostructural variables, dynamic processes or geological resources. Considering the phenomenological aspects we would like to highlight the interaction of the variables inside the hydrographical basins, like the existing relations among the different aquifer formations; the possible participation of groundwater in the hydrologic response of the fluviotorrencial system, or the quality losses of the sand of the beach as a result of the rubble dumping on the creek's margins.

Page generated in 0.1447 seconds