EFFECTS OF SENSOR SPATIAL-RESOLUTION ON LANDSCAPE STRUCTURE PARAMETERS

We examined the effects of increasing grain size from 20 m to 1100 m o n landscape parameters characterizing spatial structure in the norther n Wisconsin lake district. We examined whether structural parameters r emain relatively constant over this range and whether aggregation algo rithms permit extrapolation within this range. Images from three diffe rent satellite sensors were employed in this study: (1) the SPOT multi spectral high resolution visible(HRV), (2) the Landsat Thematic Mapper (TM), and (3) the NOAA Advanced Very High Resolution Radiometer (AVHR R). Each scene was classified as patches of water in a matrix of land. Spatial structure was quantified using several landscape parameters: percent water, number of lakes (patches), average lake area and perime ter, fractal dimension, and three measures of texture (homogeneity, co ntrast, and entropy). Results indicate that most measures were sensiti ve to changes in grain size. As grain size increased from 20 m using H RV image data to 1100 m (AVHRR), the percent water and the number of l akes decreased while the average lake area, perimeter, the fractal dim ension, and contrast increased. The other two texture measures were re latively invariant with grain size. Although examination of texture at various angles of adjacency was performed to investigate features whi ch vary systematically with angle, the angle did not have an important effect on the texture parameter values. An aggregation algorithm was used to simulate additional grain sizes. Grain was increased successiv ely by a factor of two from 20 m (the HRV image) to 1280 m. We then ca lculated landscape parameter values at each grain size. Extrapolated v alues closely approximated the actual sensor values. Because the grain size has an important effect on most landscape parameters, the choice of satellite sensor must be appropriate for the research question ask ed. Interpolation between the grain sizes of different satellite senso rs is possible with an approach involving aggregation of pixels.