Variogram analysis of high spatial resolution remote sensing data: An examination of boreal forest ecosystems

The site-specific Northwestern Ontario Forest Ecosystem Classification (NWO FEC) was adapted to provide a landscape-scale (1:20000) forest ecosystem classification for a study area located in the boreal forest of northwestern, Ontario, Canada. High spatial resolution remote sensing data were collected at two altitudes (600 m and 1150 m AGL) using the Compact Airborne Spectrographic Imager (CASI). Variogram analyses were performed on these data to determine the nature of spatial dependence of spectral reflectance for selected forest ecosystems. It was determined that an optimal size of support for characterizing forest ecosystems, as estimated by the mean ranges of a series of variograms, differed based on the altitude of the remote sensing system, indicating that different ecological units and/or processes are captured at these two altitudes. Results imply a linear aggregation of reflectance when discrete objects are not resolvable. This observation has significant implications for scaling of reflectance data, albeit restricted to a narrow range of spatial scales.