Estimates of average annual precipitation (AAP) are-needed for hydrologic modeling at Yucca Mtn., Nevada, site of a proposed, high-level nuclear waste repository. Historical precipitation data and station elevation were obtained for stations in southern Nevada and southeastern California. Elevations for 1,531 additional locations were obtained from topographic maps. The sample direct-variogram for the transformed variable TAAP = ln(AAP) * 1000 was fit with an isotropic, spherical model with a small nugget and a range of 190,000 ft. The sample direct-variogram for elevation was fit with an isotropic model with four nested structures (nugget, Gaussian, spherical, and linear) with ranges between 0 and 270,000 ft. There was a significant (p = 0.05, r = 0.75) linear correlation between TAAP and station elevation. The sample cross-variogram for TAAP and elevation was fit with two nested structures (Gaussian, spherical) with ranges from 55,000 to 355,000 ft. Alternate model structures and parameters were compared using cross-validation. Isohyetal maps for average annual precipitation (AAP) were prepared from estimates obtained by kriging and cokriging using the selected models. Isohyets based on the kriging estimates were very smooth, increasing gradually from the southwest to the northeast. Isohyets based on the cokriging estimates and the spatial correlation between AAP and elevation were more irregular and displayed known orographic effects. Indirect confirmation of the cokriging estimates were obtained by comparing isohyets prepared with the cokriging estimates to the boundaries of more densely vegetated and/or forested zones. Estimates for AAP at the repository site were 145 and 165 mm for kriging and cokriging, respectively. Cokriging reduced estimation variances at the repository site by 55% relative to kriging. The effectiveness of an existing network of stations for measuring AAP is evaluated and recommendations are made for optimal locations for additional stations. / Graduation date: 1991

Orientador: José Ricardo Sturaro / Banca: Gilda Carneiro Ferreira / Banca: César Augusto Moreira / Resumo: A viabilidade econômica da exploração de um depósito mineral envolve diversas variáveis, como teor e volume do minério, método de lavra, infraestrutura e mão de obra próxima à localização do depósito. Desta forma, se faz necessário quantificar os recursos minerais para reduzir o risco financeiro do empreendimento. A área de estudo está inserida na porção sudoeste do Greenstone Belt de Pilar de Goiás, constituída por uma sequência de metassedimentos químicos, metassedimentos clásticos, pequenos corpos intrusivos e rochas gnáissicas. As ocorrências de ouro estão associadas às camadas de clorita e grafita xistos. O objetivo deste trabalho consiste em caracterizar a distribuição espacial dos teores de ouro da mina Pilar de Goiás-GO, utilizando as técnicas de Krigagem Ordinária e Simulação Sequencial Gaussiana. O trabalho teve início com a validação do banco de dados dos furos de sondagens e a regularização das amostras para o comprimento de um metro. Com base nas descrições dos furos de sondagens, obteve-se a atitude das camadas dos litotipos, constituindo o modelo geológico que foi elaborado no programa Leapfrog Geo®. As amostras conferidas foram então submetidas às análises estatísticas e geoestatísticas. Em ambas as técnicas, realizou-se a modelagem dos variogramas e do elipsoide de busca dos dados. Para a krigagem ordinária, a filtragem restringiu os dados ao intervalo de 0 a 4,38 ppm, sendo que os outliers foram substituídos pelo valor máximo de teor. Verificou-se que os resultados obtidos pela krigagem são válidos, pois respeitam a distribuição de frequência dos dados originais. A análise da superfície do comportamento dos teores regionais permitiu concluir que não há uma direção preferencial de crescimento de teores de ouro, porém esta superfície... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The economic viability of a mineral deposit exploration involves many variables, such as content and ore volume, mining method, infrastructure and workers next to the location of the deposit. It is necessary to quantify the mineral resources to reduce the financial risk of the project. The study area is located in the southwest portion of the greenstone belt of Pilar de Goias, which is composed of a sequence of chemical and clastic metasediments, small intrusive bodies and gneissic rocks. The gold occurrences are associated with layers of chlorite schist and graphite. The objective of this study is characterize the spatial distribution of gold grades in the Pilar de Goiás mine (GO) by the Ordinary Kriging and Simulation Sequential Gaussian methods. The study started with the database validation of boreholes and the regularization of samples for the length of one meter. Based on the descriptions of the boreholes, it was obtained the attitude of the layers of rock types and, therefore, the geological model, developed in the Leapfrog Geo® program. The checked samples were then used for the statistical and geostatistical analyses. In both methods, the variograms were modeled and the search ellipsoid was defined. For Ordinary Kriging, the data filter restricted to the range 0 to 4.38 ppm and the outliers were replaced by the maximum content value. The results of kriging are valid because the frequency distribution is consistent with the original data. The analysis of the surface containing the higher levels implied that there is no preferential direction of growth of gold content, but this surface follows the regional foliation of the host rocks. The estimation by Simulation Sequential Gaussian were effective to model the layer of interest, which are the highest gold grades / Mestre

Made available in DSpace on 2014-06-11T19:29:43Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-01-25Bitstream added on 2014-06-13T20:19:55Z : No. of bitstreams: 1 dalbem_ea_me_ilha.pdf: 1384892 bytes, checksum: 9cea284026bb5d2f778f9aadfe9ac8e9 (MD5) / A cultura da cana-de-açúcar representa hoje grande fonte de divisas para o Brasil, seja pela produção de açúcar quanto pela produção de álcool etílico. A modelagem geoespacial permite a descrição quantitativa da variabilidade espacial dos atributos do solo e a estimativa não tendenciosa da variância mínima de valores desses atributos em locais não amostrados. Acessar essa variabilidade faz da geoestatística uma eficiente ferramenta de suporte na decisão do manejo do solo para incremento de produtividade das culturas. Este trabalho teve como objetivo analisar as correlações, lineares e espaciais, entre a produtividade da cana de açúcar e os atributos químicos do solo, determinando aqueles que melhor se relacionaram com o aumento da produtividade agrícola em questão. O trabalho foi realizado no município de Rubinéia (SP), cujo solo da área é um Argissolo Vermelho Eutrófico. O local das coletas de dados de fertilidade do solo e da produtividade da planta foram através da alocação de uma malha geoestatística com 121 pontos amostrais em duas profundidades (0-0,20 e 0,20-0,40m), numa área de 1,30 ha, com a distância entre os pontos de 10 x 13 metros. As análise de produtividade foram realizadas a campo por meio de contagem de número de plantas e pesagem de colmos em uma área de 9 m² por ponto amostral. A série de dados foi normal para todos os atributos tecnológicos da cana-de-açúcar, enquanto que, para os atributos do solo na profundidade de 0-0,20 m os atributos que apresentaram normalidade dos dados foram o pH, o potássio e a saturação por bases (V%), e na profundidade de 0,20-0,40 foram o pH, o teor de magnésio e a saturação por bases. A média da produtividade de colmos foi de 94,6 t ha-1 e a número de colmos com média de 11,48 colmo m2. Para os atributos do solo, os que apresentaram maiores... / The culture of sugarcane today represents big source of hard currency for Brazil, either by production of sugar or by production of ethyl alcohol. The geospatial modeling allows the quantitative description of the spatial variability of soil attributes and unbiased estimate of the minimum variance values of these attributes in locations non-sampled. Access this variability makes geostatistical an efficient decision support tool in of the soil management to increase crop productivity. This work had as objective analyze the correlations, linear and space between the productivity of sugarcane (Saccharum spp.) and soil chemical attributes, determining those that best correlated with the increase in agricultural productivity at issue. The work was conducted in the municipality of Rubinéia (SP), the soil in the area is an Red Ultisol eutrophic. Installed a geostatistical grid for data collection of soil and plant, with 121 sampling points in two depths (0-0.20 and 0.20-0.40 m), an area of 1.30 ha, with distance between dots of 10 x 13 meters. The analysis was conducted field productivity means for counting number of plants and weighing of stems in an area of 9 m² per sample point, analysis of the technological plants were performed in the laboratory of power plant Vale do Parana S/A using the methodology of CONSECANA. The data series was normal for all the technological attributes of sugarcane, whereas for the soil attributes in the 0-0.20 m depth the attributes of the data were presented normality pH, potassium (K) and base saturation (V%), and in depth from 0.20-0.40 the pH, magnesium (Mg) and V%. The average production was found in 94.6 t ha-1 and plant population obtained an average 11.48 p. m-2. For the attributes of the soil, to the highest averages were potassium layers 0-0.20 and 0.20-0.40 (K1 and K2), Magnesium layers... (Complete abstract click electronic access below)

Orientadores: Zigomar Menezes de Souza, Reginaldo Barbosa da Silva / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola / Made available in DSpace on 2018-08-23T03:01:49Z (GMT). No. of bitstreams: 1 Castioni_GuilhermeAdalbertoFerreira_M.pdf: 7918974 bytes, checksum: db6b566f58c4c70fe9c016e48a618074 (MD5) Previous issue date: 2013 / Resumo: O emprego de irrigação tem promovido alterações na função do tipo de íons e sua valência presentes na solução do solo, forma variável de pH do solo no grau de floculação crítica de partículas. O desequilíbrio e interação destes fatores podem causar alteração na dispersão da fração argila, alterando a estrutura do solo. O objetivo deste trabalho foi verificar o Delta pH do solo e sua relação com o grau de floculação e dispersão de argila no solo e então avaliar o efeito da migração de argila no adensamento do solo, bem como o aumento da compactação do solo no desenvolvimento de raízes no solo e a produtividade alcançada do feijoeiro. O experimento foi realizado na região de Cristalina-GO, em área irrigada sob pivô central, com coordenadas geográficas de 16°53'35,59" de latitude sul e 47°32'16,75" de longitude oeste, 1.021 m de altitude, o solo foi classificado como Argissolo Vermelho-Amarelo. Os atributos físicos do solo foram coletados nos pontos de cruzamento de uma malha com intervalos regulares de 10 m entre pontos em três posições ao longo do declive da área com 1,8 ha nas profundidades de 0,00-0,10, 0,10-0,20 e 0,20-0,30 m, sob um pivô central, em cada posição da encosta, ou seja, terço superior, médio e inferior foram coletados 60 pontos perfazendo o total de 180 pontos. Os dados foram submetidos à estatística descritiva, bem como a geoestatística considerando os modelos esféricos, o exponencial, o linear e o gaussiano, posteriormente, tais modelos foram usados no desenvolvimento de mapas de isolinhas (krigagem). Os resultados confirmam a predominância de carga líquida negativa pelos valores de delta pH alcançados, que provocou o elevado grau de floculação e dispersão do solo causando a movimentação de argila na vertente, contribuindo para o aumento da densidade do solo e a resistência do solo à penetração, a compactação do solo limitou o alcance do sistema radicular do feijoeiro as camadas mais profundas implicando em perdas significativas de produtividade do feijoeiro / Abstract: The use of irrigation has promoted changes in the type of ions and their valence present in the soil solution, so variable soil pH in critical flocculation of particles. The imbalance and interaction factors can cause this change in dispersion of clay, changing the soil structure. The objective of this work was to verify the Delta soil pH and its relationship to the degree of flocculation and dispersion of clay in the soil and then assess the effect of the migration of clay in soil compaction and increased soil compaction in the development of roots in the soil and the productivity achieved bean. The experiment was carried out in the region of Crystalline-GO in irrigated area under central pivot, with geographic coordinates of 16 ° 53'35, 59 "south latitude and 47 ° 32'16, 75" W, 1021 m altitude the soil was classified as Ultisol. The physical attributes of soil were collected at the intersections of a grid with intervals of 10 m between points in three positions along the slope area with 1.8 ha at depths of 0.00-0.10, 0.10 -0.20 and 0.20-0.30 m, under a center pivot at each position of the slope, ie the upper, middle and bottom were collected 60 points totaling 180 points. Data were subjected to descriptive statistics and geostatistics models considering spherical, exponential, linear, and Gaussian, then such models were used in the development of maps (kriging). The results confirm the predominance of net negative charge by the values of delta pH achieved, which caused the high degree of flocculation and dispersion of the soil causing the movement of clay in part, contributing to the increase of soil density and soil resistance to penetration soil compaction limited the scope of the root bean deeper layers resulting in significant losses in grain yield / Mestrado / Agua e Solo / Mestre em Engenharia Agrícola

Orientador: Alexandre Campane Vidal / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociências / Made available in DSpace on 2018-08-19T03:20:14Z (GMT). No. of bitstreams: 1 Carvalho_AncillaMariaAlmeidade_M.pdf: 3762992 bytes, checksum: 2ca7884e4a41caafd5d67ba3965bf9dc (MD5) Previous issue date: 2011 / Resumo: A Bacia de Taubaté, localizada na porção leste do estado de São Paulo, ocupa uma área aproximada de 2400 km², estendendo-se ao longo do Vale do Rio Paraíba, desde Jacareí até a cidade de Cruzeiro. Posicionada no segmento central do Rifte Continental do Sudeste do Brasil, seu arcabouço estrutural é formado por semi-grábens, separados por zonas de transferência ou acomodação, com depocentros invertidos sendo caracterizada pela heterogeneidade, herança geológica da tectônica rifte que compartimentou a bacia e condicionou a sedimentação de depósitos de leques aluviais associados a planícies fluviais e sedimentos lacustres. Os sedimentos da bacia formam uma das principais fontes de exploração de água do Estado de São Paulo, fornecendo alta densidade de informação para estudo em subsuperfície, como dados de poços tubulares profundos, perfis geofísicos e seções sísmicas. A revisão de dados disponíveis na bibliografia e nos órgãos destinados ao abastecimento público permitiu a construção de uma base de dados sólida para a caracterização do embasamento da bacia e dos reservatórios fluviais que a compõem. O foco deste trabalho foi a construção de um modelo geológico tridimensional do arcabouço estrutural da bacia, da distribuição de fácies sedimentares e propriedades petrofísicas, utilizando para isso métodos geoestatísticos. A delimitação do embasamento foi realizada por meio da interpolação de dados sísmicos, gravimétricos e de poços tubulares profundos realçando a presença de quatro depocentros principais na bacia. A definição das fácies sedimentares foi realizada por meio de métodos matemáticos, a partir de perfis geofísicos, e seu resultado permitiu a correlação de poços em determinada porção da bacia gerando nessa área uma melhor caracterização da distribuição dos reservatórios. Por meio de simulação estocástica foram gerados diversos cenários da distribuição das fácies sedimentares e da porosidade de um bloco situado no Compartimento São José dos Campos, sudoeste da bacia, permitindo também a obtenção de um modelo de conectividade dos aqüíferos e volume poroso do bloco estudado / Abstract: The Taubaté Basin, located in the southeastern portion of the São Paulo state, encompasses an area of approximately 2400 km², stretching along the Paraíba River Valley, from Jacareí to the Cruzeiro city. Positioned in the central segment of the Continental Rift of Southeastern Brazil, its framework is formed by half-grabens, separated by transfer zones or accommodation with reversed depocenters been characterized by heterogeneity, geological heritage of the tectonic rift that partitioned the basin and conditioned the sedimentation of alluvial fan deposits associated with the plain aluvial and lacustrine sediments. The sediments of the basin form a major source of water exploration in the São Paulo State, providing high density of information to study the subsurface, as data from deep wells, geophysical and seismic profiles. A review of available data in the literature and organs intended for public supply has allowed the construction of a solid database for the basement characterization of the basin and the reservoirs that comprise it. The focus of this work was the construction of a three-dimensional geological model of the structural framework of the basin, the distribution of sedimentary facies and petrophysical properties using geostatistical methods. The delimitation of the basement was done through the interpolation of seismic data, gravity and information from deep wells highlighting the presence of four main depocentros basin. The definition of sedimentary facies was performed by mathematical methods, based on geophysical profiles, and the result allowed the correlation of wells in a certain portion of the basin, creating a better characterization of the reservoirs distribution in this area. Through stochastic simulation various scenarios were generated of sedimentary facies distribution and porosity of a block located in Sao Jose dos Campos Compartment, southwest of the basin, allowing the obtaining of a connectivity model of aquifers and porous volume of the block studied / Mestrado / Geologia e Recursos Naturais / Mestre em Geociências

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science, Faculty of Science University of the Witwatersrand, Johannesburg 2018 / Canteen Kopje has yielded rare in-situ assemblages of the Fauresmith, a poorly defined industry often associated with the later Acheulean. The Fauresmith contains precocious developments in technology as early as ~0.5 Ma–features which only become widespread in the ensuing Middle Stone Age. The Fauresmith as a regional industry provides insight into technological practices during the period of significant behavioural diversification associated with archaic Homo sapiens. Previous excavations were conducted with relatively low spatial resolution. A new excavation, Pit 4 West, was conducted to investigate the spatial, stratigraphic and contextual association of the Fauresmith horizon in more detail. A multi-disciplinary fineresolution geoarchaeological approach was applied. A nuanced assessment of the Fauresmith’s context was developed, with macroscopic and microscopic analyses allowing for the identification of site formation processes influencing assemblages. The artefact sample size for the site was increased and the presence of diagnostic tools has aided in formally defining the Fauresmith at Canteen Kopje. / XL2019

A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Doctor of Philosophy. Johannesburg 2016 / Quantifying risk in the absence of hard data presents a significant challenge. Onshore mining of the diamondiferous linear beach deposit along the south western coast of Namibia has been ongoing for more than 80 years. A historical delineated campaign from the 1930s to 1960s used coast perpendicular trenches spaced 500 m apart, comprising a total of 26 000 individual samples, to identify 6 onshore raised beaches. These linear beaches extend offshore and are successfully mined in water depths deeper than 30 m. There is, however, a roughly 4 km wide submerged coast parallel strip adjacent to the mostly mined out onshore beaches for which no real hard data is available at present. The submerged beaches within the 4 km coast parallel strip hold great potential for being highly diamondiferous. To date hard data is not yet available to quantify or validate this potential. The question is how to obtain sufficient hard data within the techno economic constraints to enable a resource with an acceptable level of confidence to be developed. The work presented in this thesis illustrates how virtual orebodies (VOBs) are created based on geological proxies in order to have a basis to assess and rank different sampling and drilling strategies. Overview of 4 papers Paper I demonstrates the challenge of obtaining a realistic variogram that can be used in variogram-based geostatistical simulations. Simulated annealing is used to unfold the coastline and improve the detectable variography for a number of the beaches. Paper II shows how expert opinion interpretation is used to supplement sparse data that is utilised to create an indicator simulation to study the presence and absence of diamondiferous gravel. When only the sparse data is used the resultant simulation is unsuitable as a VOB upon which drilling strategies can be assessed. Paper III outlines how expert opinion hand sketches are used to create a VOB. The composite probability map based on geological proxies is adjusted using a grade profile based on adjacent onshore data before it is seeded with stones and used as a VOB for strategy testing. Paper IV illustrates how the Nachman model based on a Negative Binomial Distribution (NBD) is used to predict a minimum background grade by considering only the zero proportions (Zp) of the grade data. v Conclusions and future work In the realm of creating spatial simulations that can serve as VOBs it is very difficult to attempt to quantify uncertainty when no hard data is available. In the absence of hard data, geological proxies and expert opinion are the only inputs that can be used to create VOBs. Subsequently these VOBs are used as a base to be analysed in order to evaluate and rank different sampling and drilling strategies based on techno economic constraints. VOBs must be updated and reviewed as hard data becomes available after which sampling strategies should be reassessed. During early stage exploration projects the Zp of sample results can be used to predict a minimum background grade and rank different targets for further sampling and valuation. The research highlights the possibility that multi point statistics (MPS) can be used. Higher order MPS should be further investigated as an additional method for creating VOBs upon which sampling strategies can be assessed. / MT2017

This thesis investigates the potential of fractal dimension (FD) as a tool for enhancing airborne magnetic data. More specifically, this thesis investigates the potential of FD-based texture transform images as tools for aiding in the interpretation of airborne magnetic data. A series of different methods of estimating FD are investigated, specifically: • geometric methods (1D and 2D variation methods and 1D line divider method); • stochastic methods (1D and 2D Hurst methods and 1D and 2D semi-variogram methods), and; • spectral methods (1D and 2D wavelet methods and 1D and 2D Gabor methods). All of these methods are able to differentiate between varying theoretical FD in synthetic profiles. Moreover, these methods are able to differentiate between theoretical FDs when applied to entire profiles or in a moving window along the profile. Generally, the accuracy of the estimated FD improves when window size is increased. Similarly, the standard deviation of estimated FD decreases as window size increases. This result implied that the use of moving window FD estimates will require a trade off between the quality of the FD estimates and the need to use small windows to allow better spatial resolution. Application of the FD estimation methods to synthetic datasets containing simple ramps, ridges and point anomalies demonstrates that all of the 2D methods and most of the 1D methods are able to detect and enhance these features in the presence of up to 20% Gaussian noise. In contrast, the 1D Hurst and line divider methods can not clearly detect these features in as little as 10% Gaussian noise. Consequently, it is concluded that the 1D Hurst and line divider methods are inappropriate for enhancing airborne magnetic data. The application of these methods to simple synthetic airborne magnetic datasets highlights the methods’ sensitivity to very small variations in the data. All of the methods responded strongly to field lines some distance from the causative magnetic bodies. This effect was eliminated through the use of a variety of tolerances that essentially required a minimum level of difference between data points in order for FD to be calculated. Whilst this use of tolerances was required for synthetic datasets, its use was not required for noise corrupted versions of the synthetic magnetic data. The results from applying the FD estimation techniques to the synthetic airborne magnetic data suggested that these methods are more effective when applied to data from the pole. Whilst all of the methods were able to enhance the magnetic anomalies both at the pole and in the Southern hemisphere, the responses of the FD estimation techniques were notably simpler for the polar data. With the exception of the 1D Hurst and line divider methods, all of the methods were also able to enhance the synthetic magnetic data in the presence of 10% Gaussian noise. Application of the FD estimation methods to an airborne magnetic dataset from the Merlinleigh Sub-basin in Western Australia demonstrated their ability to enhance subtle structural features in relatively smooth airborne magnetic data. Moreover, the FD-based enhancements were able to enhance some features of this dataset better than any of the conventional enhancements considered (i.e. an analytic signal, vertical and total horizontal derivatives, and automatic gain control). Most of the FD estimation techniques enhanced similar features to each other. However, the 2D methods generally produced clearer results than their associated 1D methods. In contrast to this result, application of the FD-based enhancements to more variable airborne magnetic data from the Tanami region in the Northern Territory demonstrated that these methods are not as well suited to this style of data. The main conclusion from this work is that FD-based enhancement of relatively smooth airborne magnetic data can provide valuable input into an interpretation process. This suggests that these methods are particularly useful for aiding in the interpretation of airborne magnetic data from regions such as sedimentary basins where the distribution of magnetic sources is relatively smooth and simple. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1339560 / Thesis (Ph.D.) - University of Adelaide, Australian School of Petroleum, 2008

This thesis concerns the development, estimation and investigation of a general anisotropic spatial correlation function, within model-based geostatistics, expressed as a Gaussian linear mixed model, and estimated using residual maximum likelihood (REML). The Matern correlation function is attractive because of its parameter which controls smoothness of the spatial process, and which can be estimated from the data. This function is combined with geometric anisotropy, with an extension permitting different distance metrics, forming a flexible spatial covariance model which incorporates as special cases many infinite- range spatial covariance functions in common use. Derivatives of the residual log-likelihood with respect to the four correlation-model parameters are derived, and the REML algorithm coded in Splus for testing and refinement as a precursor to its implementation into the software ASReml, with additional generality of linear mixed models. Suggestions are given regarding initial values for the estimation. A residual likelihood ratio test for anisotropy is also developed and investigated. Application to three soil-based examples reveals that anisotropy does occur in practice, and that this technique is able to fit covariance models previously unavailable or inaccessible. Simulations of isotropic and anisotropic data with and without a nugget effect reveal the following principal points. Inclusion of some closely-spaced locations greatly improves estimation, particularly of the Matern smoothness parameter, and of the nugget variance when present. The presence of geometric anisotropy does not adversely affect parameter estimation. Presence of a nugget effect introduces greater uncertainty into the parameter estimates, most dramatically for the smoothness parameter, and also increases the chance of non-convergence and decreases the power of the test for anisotropy. Estimation is more difficult with very “unsmooth" processes (Matern smoothness parameter 0.1 or 0.25) | non- convergence is more likely and estimates are less precise and/or more biased. However it is still often possible to fit the full model including both anisotropy and nugget effect using REML with as few as 100 observations. Additional simulations involving model misspecification reveal that ignoring anisotropy when it is present can substantially increase the mean squared error of prediction, but overfitting by attempting to model anisotropy when it is absent is less damaging. Further, plug-in estimates of prediction error variance are reasonable estimates of the actual mean squared error of prediction, regardless of the model fitted, weakening the argument requiring Bayesian approaches to properly allow for uncertainty in the parameter estimates when estimating prediction error variance. The most valuable outcome of this research is the implementation of an anisotropic Matern correlation function in ASReml, including the full generality of Gaussian linear mixed models which permits additional fixed and random effects, making publicly available the facility to fit, via REML estimation, a much wider range of variance models than has previously been readily accessible. This greatly increases the probability and ease with which a well-fitting covariance model can be found for a spatial data set, thus contributing to improved geostatistical spatial analysis. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1297562 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2007

Time-series studies of ambient air pollution and acute health outcomes utilize measurements from fixed outdoor monitoring sites to assess changes in pollution concentration relative to time-variable health outcome measures. These studies rely on measured concentrations as a surrogate for population exposure. The degree to which monitoring site measurements accurately represent true ambient concentrations is of interest from both an etiologic and regulatory perspective, since associations observed in time-series studies are used to inform health-based ambient air quality standards. Air pollutant measurement errors associated with instrument precision and lack of spatial correlation between monitors have been shown to attenuate associations observed in health studies. Characterization and adjustment for air pollution measurement error can improve effect estimates in time-series studies. Measurement error was characterized for 12 ambient air pollutants in Atlanta. Simulations of instrument and spatial error were generated for each pollutant, added to a reference pollutant time-series, and used in a Poisson generalized linear model of air pollution and cardiovascular emergency department visits. This method allows for pollutant-specific quantification of impacts of measurement error on health effect estimates, both the assessed strength of association and its significance. To inform on the amount and type of error present in Atlanta measurements, air pollutant concentrations were simulated over the 20-county metropolitan area for a 6-year period, incorporating several distribution characteristics observed in measurement data. The simulated concentration fields were then used to characterize the amount and type of error due to spatial variability in ambient concentrations, as well as the impact of use of different exposure metrics in a time-series epidemiologic study. Finally, methodologies developed for the Atlanta area were applied to air pollution measurements in Dallas, Texas with consideration for the impact of this error on a health study of the Dallas-Fort Worth region that is currently underway.