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  • 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.
11

A multi-sensor approach for land cover classification and monitoring of tidal flats in the German Wadden Sea

Jung, Richard 07 April 2016 (has links)
Sand and mud traversed by tidal inlets and channels, which split in subtle branches, salt marshes at the coast, the tide, harsh weather conditions and a high diversity of fauna and flora characterize the ecosystem Wadden Sea. No other landscape on the Earth changes in such a dynamic manner. Therefore, land cover classification and monitoring of vulnerable ecosystems is one of the most important approaches in remote sensing and has drawn much attention in recent years. The Wadden Sea in the southeastern part of the North Sea is one such vulnerable ecosystem, which is highly dynamic and diverse. The tidal flats of the Wadden Sea are the zone of interaction between marine and terrestrial environments and are at risk due to climate change, pollution and anthropogenic pressure. Due to that, the European Union has implemented various directives, which formulate objectives such as achieving or maintaining a good environmental status respectively a favourable conservation status within a given time. In this context, a permanent observation for the estimation of the ecological condition is needed. Moreover, changes can be tracked or even foreseen and an appropriate response is possible. Therefore, it is important to distinguish between short-term changes, which are related to the dynamic manner of the ecosystem, and long-term changes, which are the result of extraneous influences. The accessibility both from sea and land is very poor, which makes monitoring and mapping of tidal flat environments from in situ measurements very difficult and cost-intensive. For the monitoring of big areas, time-saving applications are needed. In this context, remote sensing offers great possibilities, due to its provision of a large spatial coverage and non-intrusive measurements of the Earth’s surface. Previous studies in remote sensing have focused on the use of electro-optical and radar sensors for remote sensing of tidal flats, whereas microwave systems using synthetic aperture radar (SAR) can be a complementary tool for tidal flat observation, especially due to their high spatial resolution and all-weather imaging capability. Nevertheless, the repetitive tidal event and dynamic sedimentary processes make an integrated observation of tidal flats from multi-sourced datasets essential for mapping and monitoring. The main challenge for remote sensing of tidal flats is to isolate the sediment, vegetation or shellfish bed features in the spectral signature or backscatter intensity from interference by water, the atmosphere, fauna and flora. In addition, optically active materials, such as plankton, suspended matter and dissolved organics, affect the scattering and absorption of radiation. Tidal flats are spatially complex and temporally quite variable and thus mapping tidal land cover requires satellites or aircraft imagers with high spatial and temporal resolution and, in some cases, hyperspectral data. In this research, a hierarchical knowledge-based decision tree applied to multi-sensor remote sensing data is introduced and the results have been visually and numerically evaluated and subsequently analysed. The multi-sensor approach comprises electro-optical data from RapidEye, SAR data from TerraSAR-X and airborne LiDAR data in a decision tree. Moreover, spectrometric and ground truth data are implemented into the analysis. The aim is to develop an automatic or semi-automatic procedure for estimating the distribution of vegetation, shellfish beds and sediments south of the barrier island Norderney. The multi-sensor approach starts with a semi-automatic pre-processing procedure for the electro-optical data of RapidEye, LiDAR data, spectrometric data and ground truth data. The decision tree classification is based on a set of hierarchically structured algorithms that use object and texture features. In each decision, one satellite dataset is applied to estimate a specific class. This helps to overcome the drawbacks that arise from a combined usage of all remote sensing datasets for one class. This could be shown by the comparison of the decision tree results with a popular state-of-the-art supervised classification approach (random forest). Subsequent to the classification, a discrimination analysis of various sediment spectra, measured with a hyperspectral sensor, has been carried out. In this context, the spectral features of the tidal sediments were analysed and a feature selection method has been developed to estimate suitable wavelengths for discrimination with very high accuracy. The developed feature selection method ‘JMDFS’ (Jeffries-Matusita distance feature selection) is a filter-based supervised band elimination technique and is based on the local Euclidean distance and the Jeffries-Matusita distance. An iterative process is used to subsequently eliminate wavelengths and calculate a separability measure at the end of each iteration. If distinctive thresholds are achieved, the process stops and the remaining wavelengths are applied in the further analysis. The results have been compared with a standard feature selection method (ReliefF). The JMDFS method obtains similar results and runs 216 times faster. Both approaches are quantitatively and qualitatively evaluated using reference data and standard methodologies for comparison. The results show that the proposed approaches are able to estimate the land cover of the tidal flats and to discriminate the tidal sediments with moderate to very high accuracy. The accuracies of each land cover class vary according to the dataset used. Furthermore, it is shown that specific reflection features can be identified that help in discriminating tidal sediments and which should be used in further applications in tidal flats.
12

En beskrivning av informationsmiljö därdatumstyrda förhållanden råder : En fallstudie av en myndighet och dess informationsmiljö med rättsakter / A description of information environment in whichdate-controlled conditions apply : A case study of a government agency and its informationenvironment with legal documents

Fredriksson, Jonas, Långberg, Andreas January 2013 (has links)
In this study a case study was conducted at the Transport Agency. The government agency is seeking better alternatives to its current ways of keeping track of important dates stated in legal documents. The agency wants to explore the possibility for an IT-solution for keeping track on those dates. In the case study change analysis was conducted on the vehicle type approval process. Qualitative interviews were conducted with a section manager, vehicle type and component approvers, and with a system administrator and a system manager at the Transport Agency in Borlänge. The study describes an information environment in an organization in which date-controlled conditions apply and challenges with such an environment.The study also provides a proposal for designing an IT-solution for such an environment. The result that emerged showed that the information environment in terms of the legal documents and the institutions’ (EU and UNECE) websites where they are distributed is challenging for keeping track on dates. The challenges of the websites are that they are limited and complicated in terms of information search. The challenges with the legal documents are that date-controlled conditions apply. In other words, the dates themselves determine which dates and what applies and not. The legal documents are also many, retroactive, refer to each other and contain regulations for different kinds of areas, which makes difficult to find the relevant dates. The design proposal that emerged was made based on the existing IT environment at the Transport Agency. It was proposed that important key concepts are identified, categorized and realized in a database with searchability on the most important common concepts as denominators, and that it the information conforms with E-message. The developed database was based on date, date type, vehicle category, legal document, minor version and other info. A web interface was created in ASP.NET and C # for access to the database, with the message that a webbbased IT-solution should be considered. / I denna studie har en fallstudie genomförts på Transportstyrelsen. Myndigheten söker bättre alternativ till sin nuvarande hantering av viktiga datum som står i de juridiska dokumenten och vill undersöka möjligheten för ett IT-stöd. I fallstudien genomfördes en förändringsanalys på processen typgodkännande av fordon. Kvalitativa intervjuer gjordes med en sektionschef, handläggare för typgodkännande av fordon och komponenter samt med en systemansvarig och en systemförvaltare på Transportstyrelsen i Borlänge. Studien beskriver en informationsmiljö i en verksamhet där datumstyrda förhållanden råder samt vilka utmaningar som finns med sådan miljö. Studien ger även förslag på utformning på ett IT-stöd för sådan miljö. Resultatet som framkom är att informationsmiljön vad gäller rättsakterna i sig och institutionernas (EU och UNECE) webbsidor där de distribueras är utmanande för datumbevakning. Utmaningarna med webbsidorna är att de har begränsad och komplicerad sökning. Utmaningarna med rättsakterna är att datumstyrda förhållanden råder, det vill säga att datumen styr över varandra vad som gäller. Rättsakterna är även många, retroaktiva, hänvisar till varandra och innehåller krav om flera olika områden vilket gör det svårt att hitta de relevanta datumen. Förslaget på utformning av IT-stöd togs fram utifrån den befintliga IT-miljön på Transportstyrelsen. Förslaget var att viktiga begrepp identifieras, kategoriseras och sedan realiseras i en databas med sökbarhet på de viktigaste gemensamma begreppen som nämnare och att E-meddelande uppfylls gällande informationen. Databasen som togs fram utgick efter datum, datumtyp, fordonskategori, rättsakt, delversion och övrig info. För kommunikation mot databasen gjordes ett webbgränssnitt i ASP.NET och C# med budskapet att en webbbaserad IT-lösning bör övervägas.

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