Enhanced processing of SPOT multispectral satellite imagery for environmental monitoring and modelling

The Taita Hills in southeastern Kenya form the northernmost part of Africa’s Eastern Arc Mountains, which have been identified by Conservation International as one of the top ten biodiversity hotspots on Earth. As with many areas of the developing world, over recent decades the Taita Hills have experienced significant population growth leading to associated major changes in land use and land cover (LULC), as well as escalating land degradation, particularly soil erosion. Multi-temporal medium resolution multispectral optical satellite data, such as imagery from the SPOT HRV, HRVIR, and HRG sensors, provides a valuable source of information for environmental monitoring and modelling at a landscape level at local and regional scales. However, utilization of multi-temporal SPOT data in quantitative remote sensing studies requires the removal of atmospheric effects and the derivation of surface reflectance factor. Furthermore, for areas of rugged terrain, such as the Taita Hills, topographic correction is necessary to derive comparable reflectance throughout a SPOT scene. Reliable monitoring of LULC change over time and modelling of land degradation and human population distribution and abundance are of crucial importance to sustainable development, natural resource management, biodiversity conservation, and understanding and mitigating climate change and its impacts. The main purpose of this thesis was to develop and validate enhanced processing of SPOT satellite imagery for use in environmental monitoring and modelling at a landscape level, in regions of the developing world with limited ancillary data availability. The Taita Hills formed the application study site, whilst the Helsinki metropolitan region was used as a control site for validation and assessment of the applied atmospheric correction techniques, where multiangular reflectance field measurements were taken and where horizontal visibility meteorological data concurrent with image acquisition were available. The proposed historical empirical line method (HELM) for absolute atmospheric correction was found to be the only applied technique that could derive surface reflectance factor within an RMSE of < 0.02 ps in the SPOT visible and near-infrared bands; an accuracy level identified as a benchmark for successful atmospheric correction. A multi-scale segmentation/object relationship modelling (MSS/ORM) approach was applied to map LULC in the Taita Hills from the multi-temporal SPOT imagery. This object-based procedure was shown to derive significant improvements over a uni-scale maximum-likelihood technique. The derived LULC data was used in combination with low cost GIS geospatial layers describing elevation, rainfall and soil type, to model degradation in the Taita Hills in the form of potential soil loss, utilizing the simple universal soil loss equation (USLE). Furthermore, human population distribution and abundance were modelled with satisfactory results using only SPOT and GIS derived data and non-Gaussian predictive modelling techniques. The SPOT derived LULC data was found to be unnecessary as a predictor because the first and second order image texture measurements had greater power to explain variation in dwelling unit occurrence and abundance. The ability of the procedures to be implemented locally in the developing world using low-cost or freely available data and software was considered. The techniques discussed in this thesis are considered equally applicable to other medium- and high-resolution optical satellite imagery, as well the utilized SPOT data.

Composition operators, Aleksandrov measures and value distribution of analytic maps in the unit disc

A composition operator is a linear operator that precomposes any given function with another function, which is held fixed and called the symbol of the composition operator. This dissertation studies such operators and questions related to their theory in the case when the functions to be composed are analytic in the unit disc of the complex plane. Thus the subject of the dissertation lies at the intersection of analytic function theory and operator theory. The work contains three research articles. The first article is concerned with the value distribution of analytic functions. In the literature there are two different conditions which characterize when a composition operator is compact on the Hardy spaces of the unit disc. One condition is in terms of the classical Nevanlinna counting function, defined inside the disc, and the other condition involves a family of certain measures called the Aleksandrov (or Clark) measures and supported on the boundary of the disc. The article explains the connection between these two approaches from a function-theoretic point of view. It is shown that the Aleksandrov measures can be interpreted as kinds of boundary limits of the Nevanlinna counting function as one approaches the boundary from within the disc. The other two articles investigate the compactness properties of the difference of two composition operators, which is beneficial for understanding the structure of the set of all composition operators. The second article considers this question on the Hardy and related spaces of the disc, and employs Aleksandrov measures as its main tool. The results obtained generalize those existing for the case of a single composition operator. However, there are some peculiarities which do not occur in the theory of a single operator. The third article studies the compactness of the difference operator on the Bloch and Lipschitz spaces, improving and extending results given in the previous literature. Moreover, in this connection one obtains a general result which characterizes the compactness and weak compactness of the difference of two weighted composition operators on certain weighted Hardy-type spaces.

Expected Performance of the ATLAS Experiment - Detector, Trigger and Physics

A detailed study is presented of the expected performance of the ATLAS detector. The reconstruction of tracks, leptons, photons, missing energy and jets is investigated, together with the performance of b-tagging and the trigger. The physics potential for a variety of interesting physics processes, within the Standard Model and beyond, is examined. The study comprises a series of notes based on simulations of the detector and physics processes, with particular emphasis given to the data expected from the first years of operation of the LHC at CERN.

Metrolla muutokseen : laadullinen asennetutkimus länsimetrosta

Helsingin ja Espoon yhteinen joukkoliikennehanke länsimetro on suuri uudistus pääkaupunkiseudulla. Tutkielmassa tarkastellaan uusien metrokaupunginosien asukkaiden länsimetrohankkeeseen liittämiä asenteita sekä yleisesti metroon ja metron automatisointihankkeeseen liitettäviä asenteita. Tutkielman metodologinen lähestymistapa on sosiaalipsykologian oppiaineessa kehitetty laadullinen asennetutkimus. Metodi pohjautuu retoriseen sosiaalipsykologiaan, jossa korostetaan asioiden moniulotteista luonnetta. Sosiaalipsykologiassa on tutkittu liikennejärjestelmiä vain vähän. Ympäristön sosiaalipsykologia ja sosiaalitieteellinen liikennetutkimus muodostavat tutkielman teoreettisen viitekehyksen. Tutkielmassa metroa tarkastellaan laaja-alaisesti esimerkiksi fyysisen ympäristön osana sekä matkustuskokemuksellisena tilana. Tutkielman aineiston muodostavat lokakuussa 2010 toteutetut 10 haastattelua. Haastateltavat asuivat haastatteluhetkellä Lauttasaaressa, Tapiolassa ja Matinkylässä. Tutkielman tutkimuskysymykset on muodostettu laadullisen asennetutkimuksen kiinnostuksenkohteiden mukaisesti ja tutkielmassa tarkastellaan sitä, mitä metrokeskusteluissa oikeastaan arvotetaan eli arvioidaan kielteisesti tai myönteisesti sekä kenen (subjekti)asemasta ja miten. Arvottamisen kohteiden ja subjektiasemien tunnistaminen mahdollistaa asenteiden tunnistamisen. Tutkielman aineistossa länsimetro näyttäytyy laadultaan hyvin monimuotoisena asenteen kohteena. Metro ei ole vain liikenneväline, vaan se näyttäytyy esimerkiksi erilaisia alueita ja ihmisiä yhdistävänä tekijänä sekä pahoinvoinnin ja turvattomuuden näyttämönä. Aineiston analyysin perusteella länsimetron vastustamiseen liittyy keskeisesti pelko asuinalueiden muutoksesta. Keskeiset lähteet: Vesala & Rantanen (2007), Billig (1996), Gatersleben, Clark, Reeve & Uzzell (2007), Tvvigger-Ross, Bonaiuto & Breakwell (2003)