Mark W. Hounslow

Automatic orientation mapping of some types of soil fabric

Abstract A technique is described which can automatically delineate regions of micrographs of soils which have a similarly oriented microfabric. This is achieved by an initial pass over a digitized image using an intensity gradient algorithm to specify the orientation at each pixel. Each pixel is then given a value according to this computed direction. A second pass over the image examines the values attributed to each pixel. If, within the neighbourhood of a pixel, one particular general orientation class is dominant then the central pixel is assigned a grey-scale value appropriate to that class. The resulting image shows regions of the image which are aligned predominantly in a given direction. The resulting domain-segmented image may also be combined with the original to generate an image showing the normal grey tonal range, but overlaid with colour washes according to the general orientation of the features in the image at that location. Quantitative parameters, such as the degree and direction of preferred orientation, may be derived from both the initial intensity gradient analysis and also the domain-segmented image. All the steps may be combined in a batch processing mode to automatically analyse several images sequentially.

Ferrimagnetic Cr And Mn spinels in sediments: Residual magnetic minerals after diagenetic dissolution

Ferrimagnetic Cr-Fe and Mn-Fe spinels are the dominant remanence carrying phases in the late Triassic Lunde Formation. These have largely been identified by magnetic mineral extraction from the sediments, combined with microscopy. The extensive removal of most of the originally deposited magnetic Fe-Ti oxides during diagenesis has left the Cr-Fe and Mn-Fe spinels as a mineral residue which is resistant to dissolution. The rock magnetic signature of these minerals is not sufficiently known, to be able to identify these minerals on the basis of their magnetic properties alone.

Orientation Analysis and its Applications in Image Analysis

Publisher Summary This chapter discusses the applications of orientation analysis for microfabric studies and many different formulations of edge detectors as the merits of these are of widespread interest. With the advent of image processing and analysis techniques, there are now several methods, whereby quantification of microfabric is possible and a review of the latest developments in this field and particularly those related to orientation analysis are the subject of this chapter. In all quantitative techniques using image analysis, there are five key states—namely, (1) definition of the task, (2) image acquisition, (3) image processing, including image restoration, enhancement, edge detection, (4) image analysis, including analysis of orientation data and enhanced application of orientation analysis (e.g, domain-segmentation) and, (5) interpretation of results. The chapter focuses on both image processing and analysis. The chapter presents the edge detection and orientation analysis algorithms, which includes the development of basic formulae and also the postprocessing of results in the form of indices of anisotropy. The chapter discusses the development of general formulae for orientation analysis and a comprehensive test of many of the available formulae, including the extension of analysis using rectangular pixels and also the extension of the algorithm to three dimensions. Enhanced orientation analysis, including domain segmentation and domain mapping are discussed. Applications of orientation analysis with other techniques in image analysis, including porosity and multispectral methods are presented in the chapter.

Quantitative Orientation Analysis of Soil Microfabric

Abstract By evaluating the intensity gradients in two orthogonal directions at each pixel in digitized images of soil microfabric, it is possible to quantitatively assess the degree of orientation of features in that image. The results may be displayed as rosette diagrams, or processed further to evaluate an index of anisotropy which may be compared with external physical factors such as the stresses applied to the soil. Various formulae for deriving the intensity gradients have been considered. Simple arrays utilizing only the neighbouring pixels tend to show rosette diagrams showing a preference towards certain selected angles. More complex formulae have been developed in which any number of pixels in an array centred on the picture point of interest are included. These new formulae can provide improved estimates of the orientation of soil microfabric. The techniques described are applicable to any digitized image, and a selected number of such images of deformed clays are presented to illustrate the technique.

Quantitative methods to determine microporosity in soils and sediments

Abstract Tovey, N.K., Smart, P. and Hounslow, M.W., 1994. Quantitative methods to determine microporosity in soils and sediments. In: A.J. Ringrose-Voase and G.S. Humphreys (Editors), Soil Micromorphology: Studies in Management and Genesis. Proc. IX Int. Working Meeting on Soil Micromorphology, Townsville, Australia, July 1992. Developments in Soil Science 22, Elsevier, Amsterdam, pp. 531–539.

Automatic Analysis of Microstructure of Cohesive Sediments

Qualitative interpretation of electron micrographs of soils and sediments is both useful and necessary (see, e.g., Smart and Tovey, 1981; Grabowska-Olszewska et al., 1984; Bennett and Hulbert, 1986). However, quantitative instrumental interpretation is needed: 1. to express more precisely that which can be seen by eye; 2. to present data in a form suitable for statistical testing; 3. to retrieve information that cannot be obtained by eye; 4. to release expensive staff for productive work.