The Alpha-Tree Algorithm

A new multi-scale graph-space connectivity framework is presented. It is based upon a measure of dissimilarity between adjacent elements of the graph that is used to construct a hierarchy of partitions. Connected components or partition cells are either preserved or rejected based on a set of attribute criteria that are enumerated through logical predicates. Enforcing attribute constraints generates a dichotomy of the partition hierarchy that can be used for image segmentation and other related applications. The framework is supported by an efficient union-find based algorithm that delivers a tree representation of the totally ordered set of graph-space partitions. It is referred to as the Alpha-Tree. The practical complexity of the algorithm is linear with respect to the number of pixels. Processes on the tree can be launched interactively and in real-time, from a separate module detached from the tree construction phase. The type of attributes and attribute thresholds can be set and adjusted interactively. Timed experiments on highly complicated and massive satellite image tiles are presented, complemented by comparisons to the standard method.JRC.G.2 - Global security and crisis managemen

Rubble detection from VHR aerial imagery data using differential morphological profiles

Rubble detection is a key element in post disaster crisis assessment and response procedures. In this paper we present an automated method for rapid detection and quantification of rubble from very high resolution (VHR) aerial imagery of urban regions. It is a two step procedure in which the input image is projected on to a hierarchical representation structure for efficient mining and decomposition. Image features matching the geometric and chromatic properties of rubble are fused into a rubble layer that can be re-adjusted interactively. The targeted objects are evaluated based on a density metric given by spatial aggregation. The method is tested on a small-scale exercise on the publically available aerial imagery of Port-au-Prince, Haiti. Performance and preliminary results are discussed.JRC.G.2-Global security and crisis managemen