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2020 | Buch

Random Fields for Spatial Data Modeling

A Primer for Scientists and Engineers

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This book provides an inter-disciplinary introduction to the theory of random fields and its applications. Spatial models and spatial data analysis are integral parts of many scientific and engineering disciplines. Random fields provide a general theoretical framework for the development of spatial models and their applications in data analysis.
The contents of the book include topics from classical statistics and random field theory (regression models, Gaussian random fields, stationarity, correlation functions) spatial statistics (variogram estimation, model inference, kriging-based prediction) and statistical physics (fractals, Ising model, simulated annealing, maximum entropy, functional integral representations, perturbation and variational methods). The book also explores links between random fields, Gaussian processes and neural networks used in machine learning. Connections with applied mathematics are highlighted by means of models based on stochastic partial differential equations. An interlude on autoregressive time series provides useful lower-dimensional analogies and a connection with the classical linear harmonic oscillator. Other chapters focus on non-Gaussian random fields and stochastic simulation methods. The book also presents results based on the author’s research on Spartan random fields that were inspired by statistical field theories originating in physics. The equivalence of the one-dimensional Spartan random field model with the classical, linear, damped harmonic oscillator driven by white noise is highlighted. Ideas with potentially significant computational gains for the processing of big spatial data are presented and discussed. The final chapter concludes with a description of the Karhunen-Loève expansion of the Spartan model.
The book will appeal to engineers, physicists, and geoscientists whose research involves spatial models or spatial data analysis. Anyone with background in probability and statistics can read at least parts of the book. Some chapters will be easier to understand by readers familiar with differential equations and Fourier transforms.

Inhaltsverzeichnis

Frontmatter
Chapter 1. Introduction
Abstract
This chapter introduces various definitions and concepts that are useful in spatial data modeling: random fields, trends, fluctuations, spatial domain types, different spatial models, disorder and heterogeneity, noise and errors, inductive and empirical modeling, sampling and prediction, are among the topics discussed herein. There are also brief discussions of the connections between statistical mechanics and random fields as well as on stochastic versus nonlinear systems approaches.
Dionissios T. Hristopulos
Chapter 2. Trend Models and Estimation
Abstract
In the preceding chapter we defined the trend as the component of a random field that represents the large-scale variations. In this chapter we will discuss different approaches for estimating the trend. Trend estimation is often the first step in the formulation of a spatial model.
Dionissios T. Hristopulos
Chapter 3. Basic Notions of Random Fields
Abstract
This chapter focuses on the mathematical properties of random fields. This may seem boring or superfluous to readers who are not mathematically oriented. However, as much as the ability to discern colors is necessary to appreciate paintings, it is also necessary to develop some degree of familiarity with random field properties in order to better understand their applications.
Dionissios T. Hristopulos
Chapter 4. Additional Topics of Random Field Modeling
Abstract
We now turn our attention to specialized topics of random field modeling that include ergodicity, the concept of isotropy, the definition of different types of anisotropy, and the description of the joint dependence of random fields at more than two points. Ergodicity, isotropy and anisotropy are properties that have significant practical interest for the modeling of spatial data. On the other hand, the joint N-point dependence is a more advanced topic, primarily of modeling importance for non-Gaussian random fields. In the case of Gaussian random fields the N-point moments can be expressed in terms of the first and second-order moments.
Dionissios T. Hristopulos
Chapter 5. Geometric Properties of Random Fields
Abstract
This chapter deals with the main concepts and mathematical tools that help to describe and quantify the shapes of random fields. The geometry of Gaussian random functions is to a large extent determined by the mean and the two-point correlation functions. The classical text on the geometry of random fields is the book written by Robert Adler [10]. The basic elements of random field geometry are contained in the technical report by Abrahamsen [3]. A more recent and mathematically advanced book by Taylor and Adler exposes the geometry of random field using the language of manifolds [11].
Dionissios T. Hristopulos
Chapter 6. Gaussian Random Fields
Abstract
Gaussian random fields have a long history in science that dates back to the research of Andrey Kolmogorov and his group. Their investigation remains an active field of research with many applications in physics and engineering. The widespread appeal of Gaussian random fields is due to convenient mathematical simplifications that they enable, such as the decomposition of many-point correlation functions into products of two-point correlation functions. The simplifications achieved by Gaussian random fields are based on fact that the joint Gaussian probability density function is fully determined by the mean and the covariance function.
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Chapter 7. Random Fields Based on Local Interactions
Abstract
In this chapter we look at random fields from a perspective that is common in statistical physics but not so much in spatial data analysis. This perspective is useful, because it can lead to computationally efficient methods for spatial prediction, while it is also related with Markovian random fields. In addition, it enables the calculation of new forms of covariance functions and provides a link with stochastic partial differential equations.
Dionissios T. Hristopulos
Chapter 8. Lattice Representations of Spartan Random Fields
Abstract
Our discussion of SSRFs has so far assumed that the values of the field are defined on continuum domains \(\mathcal {D} \subset \mathbb {R}^d\). This assumption, which is inherent in the energy functional (7.​4), reflects the fact that geophysical and environmental processes take place in a spatial continuum.
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Chapter 9. Spartan Random Fields and Langevin Equations
Abstract
In this chapter we look at Spartan random fields from a different perspective. Our first goal is to show that solutions of linear stochastic partial differential (Langevin) equations are random fields with rational spectral densities [694]. In addition, the respective covariance function is the Green’s function of a suitable (i.e., derivable from Langevin equation) partial differential equation. Finally, the joint dependence of random fields that satisfy Langevin equations driven by a Gaussian white noise process can be expressed in terms of an exponential Gibbs-Boltzmann pdf; the latter has a quadratic energy function that involves local (i.e., based on low-order field derivatives) terms.
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Chapter 10. Spatial Prediction Fundamentals
Abstract
The analysis of spatial data involves different procedures that typically include model estimation, spatial prediction, and simulation. Model estimation or model inference refers to determining a suitable spatial model and the “best” values for the parameters of the model. Parameter estimation is not necessary for certain simple deterministic models (e.g., nearest neighbor method), since such models do not involve any free parameters. Model selection is then used to choose the “optimal model” (based on some specified statistical criterion) among a suite of candidates.
Dionissios T. Hristopulos
Chapter 11. More on Spatial Prediction
Abstract
This chapter begins with linear extensions of kriging that provide higher flexibility and allow relaxing the underlying assumptions on the method. Such generalizations include the application of ordinary kriging to intrinsic random fields that can handle non-stationary data, as well as the methods of regression kriging and universal kriging that incorporate deterministic trends in the linear prediction equation [338]. Cokriging allows combining multivariate information in the prediction equations. Various nonlinear extensions of kriging have also been proposed (indicator kriging, disjunctive kriging) that aim to handle non-Gaussian data.
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Chapter 12. Basic Concepts and Methods of Estimation
Abstract
In previous chapters we have tacitly assumed that the parameters of the random field model are known. An exception is Chap. 2 where we discussed regression analysis for estimating the coefficients of trend functions. However, the parameters of spatial models constructed for spatial data sets are typically not known a priori. In simulations we use spatial models with specified parameters, which have been derived from available data using model estimation procedures. This chapter examines some of the methods that can be used to estimate the model parameters from available spatial data. The focus will be on the estimation of parameters for stochastic models, instead of the simpler deterministic models examined in Chap. 10.
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Chapter 13. More on Estimation
Abstract
This chapter discusses estimation methods that are less established and not as commonly used as those presented in the preceding chapter. For example, the method of normalized correlations is relatively new, and its statistical properties have not been fully explored. The method of maximum entropy was used by Edwin Thompson Jaynes to derive statistical mechanics based on information theory [406, 407]. Following the work of Jaynes, maximum entropy has found several applications in physics [674, 753], image processing [315, 754], and machine learning [521, 561].
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Chapter 14. Beyond the Gaussian Models
Abstract
This chapter focuses on the modeling of non-Gaussian probability distributions. The main reason for discussing non-Gaussian models is the fact that spatial data often exhibit properties such as (i) strictly positive values (ii) asymmetric (skewed) probability distributions (iii) long positive tails (e.g., power-law decay of the pdf) and (iv) compact support.
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Chapter 15. Binary Random Fields
Abstract
This chapter focuses on non-Gaussian random fields that admit two different values (levels). Such fields can be used to classify objects or variables in two different groups (categories). Binary-valued random fields are also known in geostatistics as indicator random fields. Indicator random fields generated by “cutting” Gaussian random fields at some specified threshold level are commonly used. The mathematical properties and the simulation of binary random fields are discussed below.
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Chapter 16. Simulations
Abstract
Spatial interpolation generates “images” or “landscapes” of a physical process that are optimal in some specified sense as discussed in Chap. 10. This is often sufficient for a first assessment of spatial variability. However, interpolated fields tend to be overly smooth and to miss low-probability, extreme-value events. The latter are important for the assessment of environmental hazards, the estimation of mineral reserves, and the evaluation of distributed energy resources (solar, wave and aeolian). For such tasks that require a thorough analysis of the spatial variability, simulation is a more reliable tool (Fig. 16.1).
Dionissios T. Hristopulos
Chapter 17. Epilogue
Abstract
This book focuses on spatial data that can be represented by means of scalar spatial random fields defined in continuum space. Spatial data sets, on the other hand, consist of measurements collected over countable sets of points. Such measurements are treated as a sample of the underlying continuum random field.
Dionissios T. Hristopulos
Backmatter
Metadaten
Titel
Random Fields for Spatial Data Modeling
verfasst von
Prof. Dr. Dionissios T. Hristopulos
Copyright-Jahr
2020
Verlag
Springer Netherlands
Electronic ISBN
978-94-024-1918-4
Print ISBN
978-94-024-1916-0
DOI
https://doi.org/10.1007/978-94-024-1918-4

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