Medium resolution image fusion, does it enhance forest structure assessment

Abstract

This research explored the potential benefits of fusing optical and Synthetic Aperture Radar (SAR) medium resolution satellite-borne sensor data for forest structural assessment. Image fusion was applied as a means of retaining disparate data features relevant to modeling and mapping of forest structural attributes in even-aged (4-11 years) Eucalyptus plantations, located in the southern Kwazulu-Natal midlands of South Africa. Remote sensing data used in this research included the visible and near-infrared bands of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), as well as a fine beam (6.25 m resolution) RadarSAT-1 image. Both data sets were collected during the spring of 2006 and fused using a modified discrete wavelet transformation. Spatially referenced forest inventory data were also collected during this time, with 122 plots enumerated in 38 plantation compartments. Empirical relationships (optimized multiple regression) were used to test whether fused data sources produced superior statistical models. Secondary objectives of the paper included exploring the role of scale in terms of forest modelling at the plot and extended plot levels (Voroni diagrams). Results indicated that even an optimized multiple regression approach did not return accuracies suitable for plantation forestry applications (adjusted R2 of 0.55 and 0.6 for basal area and merchantable volume respectively).