166 
Percent of 
1954 
1980 
1994 
forest pixels > threshold value 
2.49 
15.38 
1.17 
non forest pixeis<threshold value 
2.87 
17.07 
7.94 
threshold value 
150 
100 
185 
Tab. 1 Forest area changes and threshold values 
3.2 Homogeneization 
A more sophisticated analysis has been carried out to 
avoid the problems above. The local gray level histogram 
has been compared with the histogram of the forest 
sample area, in each area the percentage of pixel which 
would be classified as forest with the previous scheme 
must be higher than the percentage in the sample forest 
area. 
A 5x5 pixels mask has been applied to the bina-7 map 
and the density of “forest” pixel has been evaluated. The 
central pixel has been classified as forest if the “forest” 
pixel density is equal or greater than the density in the 
sample forest area. 
A further step of the elaboration involves a mask similar to 
the previous to obtain more homogeneous forest regions. 
A final comparison has been carried out to verify the 
correspondence between the new classification and the 
“ground truth” of the ortho-photo (Fig. 12 and 13). 
Fig. 11 Step 1: binary map overlaid to the ortho-photo 
3.3 Time comparison 
A time-wise comparison has been carried out on the 
binary maps representing the forest coverage at different 
years. This allows to discriminate the forest coverage 
change over time, both in a qualitative way and in a 
quantitative way. 
Before starting the analysis the binary map have been 
split in two different regions to separate the higher part 
(more than 1000 meter above the sea level) where the 
forest coverage is more continuous, and the lower part 
where the presence of little farms and houses makes the 
forest coverage more leopard-skin looking like (between 
400 and 1000 meter above the sea level). 
Fig. 12 Step 1: binary map overlaid to the ortho-photo 
A growth trend is clearly visible in the tables below. The 
Fig. 13 Forest area coverage in 1954 
higher areas show the strongest trend. The situation in the 
lower areas is complex and both expansion and recede 
areas are present. 
Total area in square km 
11.57 
From 1954 to 1983 [%] 
67.60 
From 1954 to 1983 [Square km] 
2.3 
From 1983 to 1994 [%] 
68.30 
From 1983 to 1994 [Square km] 
0.79 
From 1954 to 1994 [%] 
67.90 
From 1954 to 1994 [Square km] 
3.09 
Tab. 2 Forest growth for areas higher than 1000 m above the 
sea level. 
Total area in square km 
15.62 
From 1954 to 1983 [%] 
32.99 
From 1954 to 1983 [Square km] 
1.1 
From 1983 to 1994 [%] 
31.15 
From 1983 to 1994 [Square km] 
0.36 
From 1954 to 1994 [%] 
32.08 
From 1954 to 1994 [Square km] 
1.46 
Tab. 3 Forest growth for areas lower than 1000 m above the 
sea level