Multi-Objective Software Suite of Two-Dimensional Shape Descriptors for Object-Based Image Analysis

TL;DR

This paper introduces a validated software suite of seven 2D shape descriptors for object-based image analysis, emphasizing physical interpretability, independence, and a novel causality-based validation method to improve geometric feature selection.

Contribution

It presents a new, validated set of 2D shape descriptors with physical meaning, along with a novel multivariate causality-based validation strategy for feature assessment.

Findings

Validated seven 2D shape descriptors for GEOBIA

Introduced a causality-based feature validation method

Provided an open-source software suite for shape analysis

Abstract

In recent years two sets of planar (2D) shape attributes, provided with an intuitive physical meaning, were proposed to the remote sensing community by, respectively, Nagao & Matsuyama and Shackelford & Davis in their seminal works on the increasingly popular geographic object based image analysis (GEOBIA) paradigm. These two published sets of intuitive geometric features were selected as initial conditions by the present R&D software project, whose multi-objective goal was to accomplish: (i) a minimally dependent and maximally informative design (knowledge/information representation) of a general purpose, user and application independent dictionary of 2D shape terms provided with a physical meaning intuitive to understand by human end users and (ii) an effective (accurate, scale invariant, easy to use) and efficient implementation of 2D shape descriptors. To comply with the Quality Assurance Framework for Earth Observation guidelines, the proposed suite of geometric functions is validated by means of a novel quantitative quality assurance policy, centered on inter feature dependence (causality) assessment. This innovative multivariate feature validation strategy is alternative to traditional feature selection procedures based on either inductive data learning classification accuracy estimation, which is inherently case specific, or cross correlation estimation, because statistical cross correlation does not imply causation. The project deliverable is an original general purpose software suite of seven validated off the shelf 2D shape descriptors intuitive to use. Alternative to existing commercial or open source software libraries of tens of planar shape functions whose informativeness remains unknown, it is eligible for use in (GE)OBIA systems in operating mode, expected to mimic human reasoning based on a convergence of evidence approach.