Recognition and Possible Remediation of Automated Tree Delineations with Multiple Isolations per Tree (Split Cases) on High-Resolution Imagery

Abstract

Individual tree crown analysis from high-resolution imagery is gaining greater use in forest applications. Automated crown delineations (isols) that are poor can cause errors in species classification and inventory estimates. This study explores the issue of recognizing split cases (e.g., tree crowns oversegmented into several isols) and demonstrates 3 remediation procedures to improve delineations. Several methods for identifying split cases are proposed, but a conceptual framework for a template-matching approach is developed further. Candidate split cases are identified where there is a good match of a template model representing the appearance of trees with the imagery, and several isols are within the template. Candidates are further analyzed through evidence such as isol shape, species class, and match of templates centered on each isol. Procedures were demonstrated with a typical individual crown isolation on 40 cm multispectral imagery of a mixed species forest in northeastern Ontario. The process showed useful effectiveness in improving the isolation, with expected omission rates of 15%–20% and 25%–30% false alarms. Overall, almost all true split cases recognized had improved crown delineations. The work shows that approaches for recognizing and remediating split cases are possible, but will have to be complex and consider multiple evidence.