1. Changes in topography result in irregularly illuminated areas and in variations in light reflection geometry. Remotely sensed data should be corrected for topographic effects, accounting for actual incidence angles. Topographic Effects on Remotely Sensed Imagery Z = sun zenith angle I = angle of incidence Surface Normal

2. Statistical-Empirical Correction for Topographic Effects Illumination: cos(i) = cos(e) cos (z) + sin(e) sin (z) cos (Ø s - Ø n ) i = angle of incidence e = surface slope z = solar zenith angle Ø s = solar azimuth angle Ø n = surface aspect Observed radiance: L OBS = b + m cos(i) Corrected radiance: L COR = L OBS - m cos(i) - b + L OBS, avrg L OBS = observed radiance (actual terrain) L COR = corrected radiance (normalized, horizontal surface) m, b = regression coefficients } at time of satellite overpass

3. 10715 ground reference points (natural forest) b = 74.9 m = 54.1 (band 4) Observed Radiance: L OBS = b + m cos(i) 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 120 110 100 90 80 70 60 50 40 30 20 cos(i)

4. Corrected Radiance: L COR = L OBS - b - m cos(i) + L OBS,avrg 10715 ground reference points (natural forest) b = 74.9 m = 54.1 (band 4) cos(i) 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 120 110 100 90 80 70 60 50 40 30 20

5. Digital Elevation Model 1200-1250 1250-1300 1300-1350 1350-1400 1400-1450 1450-1500 1500-1550 1550-1600 1600-1650 1650-1700 1700-1750 1750-1800 1800-1850 1850-1900 1900-1950 1950-2000 2000-2050 2050-2100 2100-2150 2150-2200 2200-2250 2250-2300 2300-2350 (m.a.s.l.)

6. DEM-based aspect (degrees.)DEM-based slope (degrees.)

7. Color composite original bands 742 Color composite corrected bands 742

8. USC Original Composite 742 USC Corrected Composite 742

9. Mitch Langford’s classification Unknown clusters

10. BN BP PNB PBD PC PN MS CC CT FQ CN CI YU PR Q PN C MR MC RA PNE Cluster 1 Cluster 2 Cluster 3 Cluster 4 Cluster 5 Cluster 6 Cluster 7 Airphotography-based land use USC corrected composite 453

11. Cluster 1 Cluster 2 Cluster 3 Cluster 4 Cluster 5 Cluster 6 Cluster 7 Mitch Langford’s classification USC corrected composite 453

12. Conclusions 1Satellite imagery of mountainous regions should be corrected for topographic effects before using any further. 2The statistical-empirical correction method using DEM- derived information proved to be effective and easy. 3The spatial resolution of imagery (30 m) may be insufficient to identify many small plots with different land cover. 4Image correction and classification can be further improved by using better ground reference information.