Automatic Image Classification for Planetary Exploration

Autonomous techniques in the context of planetary exploration can maximize scientific return and reduce the need for human involvement. This thesis work studies two main problems in planetary exploration: rock image classification and hyperspectral image classification. Since rock textural images are usually inhomogeneous and manually hand-crafting features is not always reliable, we propose an unsupervised feature learning method to autonomously learn the feature representation for rock images. The proposed feature method is flexible and can outperform manually selected features. In order to take advantage of the unlabelled rock images, we also propose self-taught learning technique to learn the feature representation from unlabelled rock images and then apply the features for the classification of the subclass of rock images. Since combining spatial information with spectral information for classifying hyperspectral images (HSI) can dramatically improve the performance, we first propose an innovative framework to automatically generate spatial-spectral features for HSI. Two unsupervised learning methods, K-means and PCA, are utilized to learn the spatial feature bases in each decorrelated spectral band. Then spatial-spectral features are generated by concatenating the spatial feature representations in all/principal spectral bands. In the second work for HSI classification, we propose to stack the spectral patches to reduce the spectral dimensionality and generate 2-D spectral quilts. Such quilts retain all the spectral information and can result in less convolutional parameters in neural networks. Two light convolutional neural networks are then designed to classify the spectral quilts. As the third work for HSI classification, we propose a combinational fully convolutional network. The network can not only take advantage of the inherent computational efficiency of convolution at prediction time, but also perform as a collection of many paths and has an ensemble-like behavior which guarantees the robust performance

Dialectical GAN for SAR Image Translation: From Sentinel-1 to TerraSAR-X

Contrary to optical images, Synthetic Aperture Radar (SAR) images are in different electromagnetic spectrum where the human visual system is not accustomed to. Thus, with more and more SAR applications, the demand for enhanced high-quality SAR images has increased considerably. However, high-quality SAR images entail high costs due to the limitations of current SAR devices and their image processing resources. To improve the quality of SAR images and to reduce the costs of their generation, we propose a Dialectical Generative Adversarial Network (Dialectical GAN) to generate high-quality SAR images. This method is based on the analysis of hierarchical SAR information and the "dialectical" structure of GAN frameworks. As a demonstration, a typical example will be shown where a low-resolution SAR image (e.g., a Sentinel-1 image) with large ground coverage is translated into a high-resolution SAR image (e.g., a TerraSAR-X image). Three traditional algorithms are compared, and a new algorithm is proposed based on a network framework by combining conditional WGAN-GP (Wasserstein Generative Adversarial Network - Gradient Penalty) loss functions and Spatial Gram matrices under the rule of dialectics. Experimental results show that the SAR image translation works very well when we compare the results of our proposed method with the selected traditional methods.Comment: 22 pages, 15 figure

An optimal multiedge detector for SAR image segmentation,”

Abstract-Edge detection is a fundamental issue in image analysis. Due to the presence of speckle, which can be modeled as a strong, multiplicative noise, edge detection in synthetic aperture radar (SAR) images is extremely difficult, and edge detectors developed for optical images are inefficient. Several robust operators have been developed for the detection of isolated step edges in speckled images. We propose a new step-edge detector for SAR images, which is optimal in the minimum mean square error (MSSE) sense under a stochastic multiedge model. It computes a normalized ratio of exponentially weighted averages (ROEWA) on opposite sides of the central pixel. This is done in the horizontal and vertical direction, and the magnitude of the two components yields an edge strength map. Thresholding of the edge strength map by a modified version of the watershed algorithm and region merging to eliminate false edges complete an efficient segmentation scheme. Experimental results obtained from simulated SAR images as well as ERS-1 data are presented. Index Terms-Edge detection, multiedge model, region merging, segmentation, speckle, synthetic aperture radar (SAR), watershed algorithm

Building change detection from remotely sensed data using machine learning techniques

As remote sensing data plays an increasingly important role in many fields, many countries have established geographic information systems. However, such systems usually suffer from obsolete scene details, making the development of change detection technology critical. Building changes are important in practice, as they are valuable in urban planning and disaster rescue. This thesis focuses on building change detection from remotely sensed data using machine learning techniques. Supervised classification is a traditional method for pixel level change detection, and relies on a suitable training dataset. Since different training datasets may affect the learning performance differently, the effects of dataset characteristics on pixel level building change detection are first studied. The research is conducted from two angles, namely the imbalance and noise in the training dataset, and multiple correlations among different features. The robustness of some supervised learning algorithms to unbalanced and noisy training datasets is examined, and the results are interpreted from a theoretical perspective. A solution for handling multiple correlations is introduced, and its performance on and applicability to building change detection is investigated. Finally, an object-based post processing technique is proposed using prior knowledge to further suppress false alarms. A novel corner based Markov random field (MRF) method is then proposed for exploring spatial information and contextual relations in changed building outline detection. Corners are treated as vertices in the graph, and a new method is proposed for determining neighbourhood relations. Energy terms in the proposed method are constructed using spatial features to describe building characteristics. An optimal solution indicates spatial features belonging to changed buildings, and changed areas are revealed based on novel linking processes. Considering the individual advantages of pixel level, contextual and spatial features, an MRF based combinational method is proposed that exploits spectral, spatial and contextual features in building change detection. It consists of pixel level detection and corner based refinement. Pixel level detection is first conducted, which provides an initial indication of changed areas. Corner based refinement is then implemented to further refine the detection results. Experimental results and quantitative analysis demonstrate the capacity and effectiveness of the proposed methods

Feature Based Segmentation of Colour Textured Images using Markov Random Field Model

The problem of image segmentation has been investigated with a focus on colored textured image segmentation.Texture is a substantial feature for the analysis of different types of images. Texture segmentation has an assortment of important applications ranging from vision guided autonomous robotics and remote sensing to medical diagnosis and retrieval in large image databases. But the main problem with the textured images is that they contain texture elements of various sizes and in some cases each of which can itself be textured.Thus the texture image segmentation is widely discerned as a difficult and thought-provoking problem.In this thesis an attempt has been made to devise methodologies for automated color textured image segmentation scheme. This problem has been addressed in the literature, still many key open issues remain to be investigated. As an initial step in this direction, this thesis proposes two methods which address the problem of color texture image segmentation through feature extraction approach in partially supervised approach.The feature extraction approaches can be classified into feature based and model based techniques.In feature based technique features are assessed without any model in mind. But in case of model based approach an inherent mathematical model lets eatures to be measured by fitting the model to the texture.The inherent features of the texture are captured in a set of parameters in order to understand the properties generating the texture. Nevertheless, a clear distinction can not be made between the two approaches and hence a combination of approaches from different categories is frequently adopted. In textured image segmentation, image model assumes a significant role and is developed by capturing salient spatial properties of an image. Markov random field (MRF)theory provides a convenient and consistent way to model context dependent entities.In this context a new scheme is proposed using Gaussian MRF model where the segmentation problem is formulated as a pixel labeling problem.The a priori class labels are modeled as Markov random field model and the number of classes is known a priori in partially supervised framework.The image label estimation problem is cast in Bayesian framework using Maximum a Posteriori (MAP)criterion and the MAP estimates of the image labels are obtained using iterated conditional modes (ICM) algorithm. Though the MRF model takes into account the local spatial interactions, it has a limitation in modeling natural scenes of distinct regions. Hence in our formulation, the first scheme takes into account within and between color plane interactions to incorporate spectraland contextual features. Genetic algorithm is employed for the initialization of ICM algorithm to obtain MAP estimates of image labels. The faster convergence property of the ICM algorithm and global convergence property of genetic algorithm are hybridized to obtain segmentation with better accuracy as well as faster convergence

Statistical Feature Selection and Extraction for Video and Image Segmentation

The purpose of this study was to develop statistical feature selection and extraction methods for video and image segmentation, which partition a video or image into non-overlap and meaningful objects or regions. It is a fundamental step towards content-based visual information analysis. Visual data segmentation is a difficult task due to the various definitions of meaningful entities, as well as their complex properties and behaviors. Generally, visual data segmentation is a pattern recognition problem, where feature selection/extraction and data classifier design are two key components. Pixel intensity, color, time, texture, spatial location, shape, motion information, etc., are most frequently used features for visual data representation. Since not all of features are representative regarding visual data, and have significant contribution to the data classification, feature selection and/or extraction are necessary to select or generate salient features for data classifier. Statistical machine learning methods play important roles in developing data classifiers. In this report, both parametric and nonparametric machine learning methods are studied under three specific applications: video and image segmentation, as well as remote sensing data analysis. For various visual data segmentation tasks, key-frame extraction in video segmentation, WDHMM likelihood computation, decision tree training, and support vector learning are studied for feature selection and/or extraction and segmentation. Simulations on both synthetic and real data show that the proposed methods can provide accurate and robust segmentation results, as well as representative and discriminative features sets. This work can further inspire our studies towards the real applications. In these applications, we are able to obtain state-of-the-art or promising results as well as efficient algorithmsElectrical Engineering Technolog