Seasonal changes of Minnaert topographic normalization constants (Ks) in rugged deciduous forest areas

Minnaert constants (K) were derived for two contiguous deciduous forest areas in northern Apennines (beech, 366 ha, and mixed deciduous forest, 343 ha) from non-atmospherically corrected, multi-temporal Landsat TM data (band 3, 4 and 5) collected on different periods of the growing season (April-August). Calculated Minnaert K values for both forest types were markedly dependent on the period of the growing season with K values ranges for the two forest types and all dates of 0.21-0.50, 0.49-0.67 and 0.58-0.87 for bands 3, 4 and 5 respectively. These K values estimates were calculated with an r significance level range of 0.74-0.94, indicating a consistent behaviour of the Minnaert model from image to image. The correlation factors between uncorrected TM bands 3, 4 and 5 and the cosine of solar illumination angle (i) ranged from 0.68 to 0.94. Minnaert normalization was effective at removing the topographic effect reducing the correlation coefficients of the three corrected bands with cos(i) within the range -0.11/+0.02 for all dates