• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1
  • 1
  • 1
  • Tagged with
  • 3
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 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.
1

Fractals and fuzzy sets for modelling the heterogenity and spatial complexity of urban landscapes using multiscale remote sensing data

Islam, Zahurul January 2004 (has links)
This research presents models for the analysis of textural and contextual information content of multiscale remote sensing to select an appropriate scale for the correct interpretation and mapping of heterogeneous urban land cover types. Spatial complexity measures such as the fractal model and the Moran’s I index of spatial autocorrelation were applied for addressing the issue of scale, while fuzzy set theory was applied for mapping heterogeneous urban land cover types. Three local government areas (e.g. the City of Perth, the City of Melville and the City of Armadale) of the Perth metropolitan area were selected, as the dominant land covers of these areas are representative to the whole metropolitan area, for the analysis of spatial complexity and the mapping of complex land covers. Characterisation of spatial complexity of the study areas computed from SPOT, Landsat-7 ETM+, and Landsat MSS was used for assessing the appropriateness of a scale for urban analysis. Associated with this outcome, the effect of spectral resolution and land cover heterogeneity on spatial complexity, the performance of fractal measurement algorithms and the relationship between the fractal dimension and Moran’s I were identified. A fuzzy supervised approach of the fuzzy c-means algorithm was used to generate fuzzy memberships of the selected bands of a Landsat-7 ETM+ scene based on the highest spectral separability among different urban land covers (e.g. forest, grassland, urban and dense urban) as determined by a transformed divergence analysis. Fuzzy land cover maps resulting from the application of fuzzy operators (e.g. maximum, minimum, algebraic sum, algebraic product and gamma operators) were evaluated against fuzzy memberships derived from the virtual field reference database (VFRDB). / The performance of fuzzy operators in generating fuzzy categorical maps along with the effect of land cover heterogeneity on fuzzy accuracy measures and sources of classification error were assessed. The analysis of spatial complexity computed from remote sensing images using a fractal model indicated that the various urban land cover types of the Perth metropolitan area are best represented at a resolution of 20 m (SPOT) as the fractal dimension (D) was found higher, as compared to the 25 m and 50 m resolutions of the Landsat-7 ETM+ and Landsat MSS, respectively, demonstrated the ability of the fractal model in distinguishing variations in the composition of built-up areas in the green and red bands of the satellite data, while forested areas typical of the urban fringe appear better characterised in the NIR band. Moran’s I of spatial autocorrelation was found useful in describing the spatial pattern of urban land cover types. A comparison between the D and Moran’s I of the study areas revealed a negative correlation, indicating that the higher the Moran’s I, the lesser the fractal dimension indicating a lower spatial complexity. Likewise, the results The accuracy of the fuzzy categorical maps associated with multiple spectral bands of a Landsat-7 ETM+ scene using various fuzzy operators reveals that the fuzzy gamma operator (y = 0.90) outperformed the categorical accuracy measures obtained by applying the fuzzy algebraic sum and other fuzzy operators for the City of Perth, while the accuracy measures of y value of 0.95 were found highest for the City of Melville and the City of Armadale. / A comparison of the accuracy measures of the fuzzy land cover maps of the study areas indicated that the overall accuracy of the City of Perth was up to 13% higher than the overall accuracy of the City of Melville and the City of Armadale which was found 69% and 71%, respectively. The lower accuracy measures of the City of Melville and the City of Armadale was attributed to highly mixed land cover classes resulting in mixed pixels in Landsat-7 ETM+ scene. In addition, the spectral similarity among the class forest and grassland, urban and dense urban were identified as sources of classification errors. The analysis of spatial complexity using multiscale and multisource remote sensing data and the application of fuzzy set theory provided a viable methodology for assessing the appropriateness of scale selection for an urban analysis and generating fuzzy urban land cover maps from a multispectral image. It also illustrated the longstanding issue of carrying out the accuracy of the fuzzy land cover map considering the fuzzy memberships of the classified data and the reference data using a fuzzy error matrix.
2

Περιβαλλοντική χαρτογράφηση στην Καλαμάτα με δορυφορικές εικόνες Aster

Σκούντζου, Άννα-Χαραλαμπία 07 April 2011 (has links)
Οι δορυφορικές εικόνες ASTER αποτελουν το πιο πρόσφατο προϊόν της διαστημικής τεχνολογίας. Έχει πολύ μεγάλη φασματική διακριτική ικανότητα σε σημείο που να χαρακτηρίζεται από αρκετούς επιστήμονες σαν ένα υπερφασματικό καταγραφικό σύστημα στο υπέρυθρο. Έτσι δίνονται νέες δυνατότητες για την ερμηνεία είτε ποιοτικά είτε ποσοτικά καλύψεων γης και φυσικών καταστάσεων της γήινης επιφάνειας. Ο σκοπός είναι η περιβαλλοντική χαρτογράφηση του Νομού Μεσσηνίας από δορυφορικές εικόνες ASTER προκειμένου να χαρτογραφηθούν οι φυσικοί πόροι και οι καλύψεις γης. Έτσι θα μπορέσουμε να αξιολογήσουμε τις δυνατότητες και τις εφαρμογές που έχουν αυτά τα δεδομένα. Μετά τις διορθώσεις (αποζωνοποίηση, μετατροπή σε τιμές ενέργειας κ.ά) η ταξινόμηση της δορυφορικής εικόνας μας επέτρεψε να διακρίνουμε τις παρακάτω κατηγορίες: καλλιέργειες, ποώδη βλάστηση, δύο τύπους δάσους, αστική γη, υδάτινες επιφάνειες, σύννεφα και εντελώς γυμνό από βλάστηση έδαφος και να δημιουρφήσουμε ένα θεματικό χάρτη. Εάν χρησημοποιηθούν περισσότερα κανάλια και όχι μόνο 3, τότε θα γίνει δυνατή η χαρτογράφηση περισσότερων κατηγοριών μόνο που η ταυτοποίηση της κάθε κατηγορίας θα μπορεί να πραγματοποιηθεί μόνο με εργασίες πεδίου στο ύπαιθρο. / Satellite pictures ASTER constituting the most recent product of space technology. It has very big spectrum discreet faculty in point that would be characterized by enough scientists as a super-spectrum recorder system in infra red. Thus are given new possibilities for the interpretation of either qualitatively or quantitatively covers of ground and natural situations of earthy surface. The aim is the environmental mapping of Prefecture Messinia from satellite pictures ASTER so that be charted the natural resources and the covers of ground. Thus we might evaluate the possibilities and the applications that have these data. Afterwards the corrections (transformation in prices of energy etc) the classification of satellite picture allowed us to distinguish the following categories: cultivation, underbrush, two types of forest, urban ground, aquatic surfaces, clouds and completely naked from vegetation ground and create a thematic map. If more channels and not only 3 be used, then becomes possible the mapping of more categories only that the identification of each category might be realized only with work of field in the countryside.
3

Evaluación de la biodiversidad en el mosaico urbano de la ciudad de Pichilemu, Región del Libertador General Bernardo O'Higgins

Riquelme Negrete, Sebastian January 2019 (has links)
Memoria para optar al título de Geógrafo / En los últimos años la ciudad de Pichilemu ha experimentado un sostenido crecimiento físico y demográfico por influencia de la actividad turística, ocasionando una presión creciente sobre áreas de alto valor ecológico, y por ende, alteraciones en la biodiversidad local. Siguiendo la tendencia de América Latina, Chile posee un déficit de estudios de ecología urbana, motivo por el cual esta memoria contribuye evaluando la biodiversidad de avifauna y vegetación leñosa en las coberturas de suelo del mosaico urbano de Pichilemu. El levantamiento de información de biodiversidad se llevó a cabo mediante conteo de aves e inventarios florísticos entre el período estival del 2017 y el de 2018. Con esta información se calculó riqueza, abundancia, tres índices de diversidad alfa (Shannon-Wiener, Pielou y Simpson), en conjunto con los porcentajes de especies endémicas, nativas y amenazadas. Además, se analizó si la distancia entre los puntos de muestreo y los componentes de infraestructura verde diversos en Shannon influencia la distribución espacial de los valores de los parámetros de diversidad alfa. Paralelamente se clasificaron las especies de avifauna en gremios tróficos y según su grado de sensibilidad a la urbanización. Asimismo, se compararon las coberturas de suelo en función de su biodiversidad a través del test de Kruskall-Wallis y el test de Dunn. Por último, se realizó un análisis de clúster para ver la similitud entre las coberturas de suelo. Los resultados señalan un patrón bimodal en el índice de Shannon, pues existen dos grupos de coberturas de suelo que presentan los valores máximos en esta variable en Pichilemu. El primero de ellos, con los valores más altos del índice de Shannon, está compuesto por coberturas naturales tales como los humedales y cuerpos de agua, quebradas y cursos de agua, y matorral arborescente. El otro grupo, con los segundos valores más altos del índice de Shannon, está integrado por coberturas híbridas como el tejido urbano continuo y el tejido urbano discontinuo. En Pichilemu, las especies de avifauna son mayoritariamente nativas, mientras que gran parte de las especies de vegetación leñosa son exóticas, muchas de ellas siendo exóticas invasoras. A pesar de su alta diversidad, el tejido urbano continuo alberga casi todos los individuos pertenecientes a una especie urban exploiter (Passer domesticus). Al contrario, los individuos de las especies urban avoiders se concentran en coberturas diversas y poco intervenidas como los humedales y cuerpos de agua, quebradas y cursos de agua, playas, dunas y arenales, y el matorral arborescente. Al mismo tiempo, estas coberturas naturales son las que exhiben la mayor cantidad de gremios tróficos. Respecto al análisis de correlación, la distancia entre los puntos de muestreo y las coberturas correspondientes a componentes de infraestructura verde diversos en Shannon no explica totalmente la variabilidad de los parámetros de diversidad alfa. Mediante el análisis de clúster, se destacan los altos niveles de diversidad del conglomerado compuesto por los humedales y cuerpos de agua, quebradas y cursos de agua, matorral arborescente, matorral pradera, y las plantaciones, De este modo, se concluye que estas coberturas deberían ser priorizadas para las labores de restauración ecológica y conservación de la biodiversidad. / Throughout the last years, the city of Pichilemu has undergone a sharp spatial and demographic growth influenced partly by tourist activity, which it caused an increasing pressure on high ecological value areas and local biodiversity. Following the same trend as in Latin America, Chile has few studies on urban ecology; hence this study contributes with an assessment of avifauna and woody vegetation biodiversity in land covers belonging to the urban mosaic of Pichilemu. All field samplings were conducted during 2017 and 2018 summer times using bird counting and floristic inventories. Richness, abundance, alpha diversity indexes (Shannon-Wiener, Pielou and Simpson) of species were calculated, along with the proportion of endemic, native and threatened species. Moreover, the distance between sampling points and diverse components of the green infrastructure of Pichilemu city was analysed to demonstrate whether it influences the spatial distribution of alpha diversity parameters values. Avifauna species were classified into trophic guilds and three distinct categories (urban exploiter, urban adapter and urban avoider) basing on their response to urbanisation. Furthermore, in order to compare land covers regarding their biodiversity, Kruskal-Wallis and Dunn's test were applied. Finally, a cluster analysis was carried out to see the similarity among land covers and sampling points. The results show a bimodal distribution pattern on the Shannon index, since there are two groups of land covers with maximum values both in avifauna and woody vegetation in Pichilemu. The most diverse group in Shannon index is made up of natural land covers such as wetlands and water bodies, streams and water courses and tree-shaped scrubland. The second most diverse group in Shannon index is made up of hybrid land covers such as continuous urban fabric and discontinuous urban fabric. Most of avifauna species are native whilst the majority of woody vegetation species are exotic in Pichilemu. Even though continuous urban fabric is diverse, almost all individuals of avifauna belong to an urban exploiter species (Passer domesticus). On the other hand, individuals belonging to urban avoider species are prone to be found in diverse and less disturbed land covers such as wetlands and water bodies, streams and water courses, strands, dunes and sandbanks and tree-shaped scrubland. Likewise, these land covers contain the highest number of trophic guilds of avifauna. Regarding correlation analysis, the distance between sampling points and diverse green infrastructure components does not explain completely the spatial variability of alpha diversity parameters. Through cluster analysis, cluster comprised of wetlands and water bodies, streams and water courses, tree-shaped scrubland, shrub brush and plantations has outstanding diversity values. Therefore, these land covers should be prioritised for ecological restoration and biodiversity conservation measures.

Page generated in 0.081 seconds