Properties of design-based estimation under stratified spatial sampling with application to canopy coverage estimation

The estimation of the total of an attribute defined over a continuous planar domain is required in many applied settings, such as the estimation of canopy coverage in the Monterano Nature Reserve in Italy. If the design-based approach is considered, the scheme for the placement of the sample sites over the domain is fundamental in order to implement the survey. In real situations, a commonly adopted scheme is based on partitioning the domain into suitable strata, in such a way that a single sample site is uniformly placed (i.e., selected with uniform probability density) in each stratum and sample sites are independently located. Under mild conditions on the function representing the target attribute, it is shown that this scheme gives rise to an unbiased spatial total estimator which is "superefficient" with respect to the estimator based on the uniform placement of independent sample sites over the domain. In addition, the large-sample normality of the estimator is proven and variance estimation issues are discussed.Comment: Published in at http://dx.doi.org/10.1214/11-AOAS509 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Design-Based Treatment of Unit Nonresponse by the Calibration Approach

The use of nonresponse calibration weighting is considered in a complete design-based frameworkto account for the cases in which nonresponse is a fixed characteristic of the units, just like the interest variable. Approximate expressions of design-based bias and variance of the calibration estimator are derived and some estimators of the sampling variance are proposed. The choice of auxiliary variables is discussed from theoretical and practical point of view. The results of an extensive simulation study demonstrate how the reliability of the procedure is mainly determined by the capability of selecting auxiliary variables in such a way that their relationship with the interest variable is similar for both the respondent and nonrespondent sub-populations.auxiliary variables, calibration estimator, variance estimator, simulation study.

PROYECTO ESTRUCTURAL DE UNA NAVE INDUSTRIAL PARA LA EXPOSICIÓN Y VENTA DE AUTOMÓVILES SITUADA EN EL POLÍGONO INDUSTRIAL DE MAHÓN EN MENORCA

[ES] Este Trabajo de Fin de Grado tiene por objeto diseñar, calcular y presupuestar la estructura, cimentaciones y cerramientos de una nave industrial para un concesionario de coches, que incluye una zona de exposición y otra de oficinas para administración y venta. La tipología del edificio es una nave a dos aguas con altillo. La nave se ubica en el polígono industrial de Mahón (POIMA), en Menorca. El dimensionado de la estructura y de las cimentaciones y el presupuesto se realiza con el software CYPE Ingenieros. La edición de planos se lleva a cabo con AutoCad. Todos los cálculos y comprobaciones de los sistemas estructurales tienen en cuenta las vigentes normativas: Código Técnico de Edificación (CTE-DB-SE-A) y Instrucción Española del Hormigón Estructural (EHE-08).[EN] The purpose of this Final Degree Project is to design, calculate and budget the structure, foundations and enclosures of an industrial warehouse for a car dealership, which consists of an exhibition area and an area for the administrative and sales offices. The typology of the building is a gabled warehouse with a mezzanine floor. The warehouse is located in the industrial park of Mahón industrial park (POIMA), in Menorca. The structure and foundations design and calculations, as well as the budget, are obtained by means of ¿CYPE Ingenieros¿ software. The structural plans edition is done with ¿AutoCad¿. All the calculations and verifications of the structural systems take into consideration the current regulations: Technical Building Code (CTE-DB-SE-A) and Spanish Instruction of Structural Concrete (EHE-08).Franceschi, S. (2021). PROYECTO ESTRUCTURAL DE UNA NAVE INDUSTRIAL PARA LA EXPOSICIÓN Y VENTA DE AUTOMÓVILES SITUADA EN EL POLÍGONO INDUSTRIAL DE MAHÓN EN MENORCA. Universitat Politècnica de València. http://hdl.handle.net/10251/168859TFG

Design-based spatial interpolation with data driven selection of the smoothing parameter

In the inverse distance weighting interpolation the interpolated, value is a weighted mean of the sampled values, with weights decreasing with the distances. The most widely adopted class of distance functions is the class of negative powers of order α and the appropriate choice of the smoothing parameter α is a crucial issue. In this paper, we give sufficient conditions for the design-based consistency of the inverse distance weighting interpolator when α is selected by cross-validation techniques, and a pseudo-population bootstrap approach is introduced to estimate the accuracy of the resulting interpolator. A simulation study is performed to empirically confirm the theoritical findings and to investigate the finite-sample properties of the interpolator obtained using leave-one-out cross-validation. Moreover, a comparison with the nearest neighbor interpolator, which is the limiting case for α = ∞, is performed. Finally, the estimation of the surface of the Shannon diversity index of tree diameter at breast height in the experimental watershed of Bonis forest (Southern Italy) is described

Some empirical results on nearest-neighbour pseudo-populations for resampling from spatial populations

In finite populations, pseudo-population bootstrap is the sole method preserving the spirit of the original bootstrap performed from iid observations. In spatial sampling, theoretical results about the convergence of bootstrap distributions to the actual distributions of estimators are lacking, owing to the failure of spatially balanced sampling designs to converge to the maximum entropy design. In addition, the issue of creating pseudo-populations able to mimic the characteristics of real populations is challenging in spatial frameworks where spatial trends, relationships, and similarities among neighbouring locations are invariably present. In this paper, we propose the use of the nearest-neighbour interpolation of spatial populations for constructing pseudo-populations that converge to real populations under mild conditions. The effectiveness of these proposals with respect to traditional pseudo-populations is empirically checked by a simulation stud

Mapping by spatial predictors exploiting remotely sensed and ground data: a comparative design-based perspective

This study was designed to compare the performance – in terms of bias and accuracy – of four different parametric,semiparametric and nonparametric methods in spatially predicting a forest response variable using auxiliary information from remote sensing. The comparison was carried out in simulated and real populations where the value of response variable was known for each pixel of the study region. Sampling was simulated through a tessellation stratified design. Universal kriging and cokriging were considered among parametric methods based on the spatial autocorrelation of the forest response variable. Locallyweighted regression and k-nearest neighbor predictors were considered among semiparametric and nonparametricmethods based on the information from neighboring sites in the auxiliary variable space. The study was performed from a design-based perspective, taking the populations as fixed and replicating the sampling procedurewith 1000Monte Carlo simulation runs. On the basis of the empirical values of relative bias and relative root mean squared error it was concluded that universal kriging and cokriging were more suitable in the presence of strong spatial autocorrelation of the forest variable, while locally weighted regression and k-nearest neighbors were more suitable when the auxiliary variables were well correlated with the response variable. Results of the study advise that attention should be paid when mapping forest variables characterized by highly heterogeneous structures. The guidelines of this study can be adopted even for mapping environmental attributes beside forestry

On the extreme hydrologic events determinants by means of Beta-Singh-Maddala reparameterization

In previous studies, beta-k distribution and distribution functions strongly related to that, have played important roles in representing extreme events. Among these distributions, the Beta-Singh-Maddala turned out to be adequate for modelling hydrological extreme events. Starting from this distribution, the aim of the paper is to express the model as a function of indexes of hydrological interest and simultaneously investigate on their dependence with a set of explanatory variables in such a way to explore on possible determinants of extreme hydrologic events. Finally, an application to a real hydrologic dataset is considered in order to show the potentiality of the proposed model in describing data and in understanding effects of covariates on frequently adopted hydrological indicators

On the verge between Ancient and Modern Times. A linguistic analysis of Urban Exploration practices

Recently the fascination with the aesthetics of abandoned places has stepped into the limelight as a new form of tourism known as Urbex or Urban Exploration, which involves discovering abandoned places and reporting the exploration with documentary evidence on specialized websites and blogs. This paper aims to investigate online discourse on Urbex by analyzing how urban exploration is talked about in two different online spaces, i.e., interest-based communities where discussion about the activity of visiting abandoned places among members is fostered and encouraged (Reddit), and more public, monologic spaces, such as blogs and websites, where longer texts are produced with a more descriptive/commercial purpose. To reach this goal, a comparative analysis of keywords and selected key terms was carried out on two ad-hoc corpora, i.e., the Urban Website Corpus (UW-Corpus) and the Urban Reddit Corpus (UR-Corpus). Results show that the linguistic choices of urban explorers highlight the existence of tension between the core tenets and ethical principles of urban exploration - avoiding disclosure of exact location, focusing on sites disregarded by preservationists, awareness of legal repercussions for trespassing - and a shift towards a more mainstream, regulated type of activity. In the UR-Corpus, distinctive language forms suggest that Urbex aficionados constitute a discourse community