Wetland mapping with LiDAR derivatives, SAR polarimetric decompositions, and LiDAR–SAR fusion using a random forest classifier

Abstract

In this paper, we assess the use of Random Forest (RF) for mapping land cover classes within Mer Bleue bog, a large northern peatland in southeastern Ontario near Ottawa, Canada, using Synthetic Aperture Radar (SAR) and airborne Light Detection and Ranging (LiDAR). Not only has RF been shown to improve classification accuracies over more traditional classifiers, but it also provides useful information on the statistical importance of individual input image bands for land cover classification. Our specific objectives in this study were to: (i) assess the robustness of a RF approach to northern peatland classification; (ii) examine variable importance resulting from the RF classifications to identify which imagery types, derivatives, and analysis scales are most useful for mapping different classes of northern peatlands; (iii) assess if fusion of different LiDAR and SAR variables can improve classification accuracies at Mer Bleue; and (iv) assess physical interpretability of the multisensor image types and derivatives with respect to biophysical attributes associated with peatland classes. Our results show that the fusion of SAR with LiDAR imagery and derivatives at this study site did not provide additional classification accuracy over the use of LiDAR derivatives alone. Nevertheless, the RF-based approach presented here has strong potential to improve mapping and imagery classification of wetlands and may also help researchers and practitioners improve information extraction and land cover classification in other application areas benefitting from large volumes of multi-sensor imagery.