415 
Figure 5. Density slices of the ratios and differences. The white 
and black areas represent areas of extreme change. 
extreme change. These areas, such as the change from grass (low-density) 
in the BW scene to water (high-density) in the color scene, mapped out 
correctly, while areas of less extreme change in density contained 
identification errors. These errors ranged from minor, such as un 
changed grass areas being classified as less extreme change, to major, 
such as classifying the area of a new building as not having changed. 
Although the sun angle and the temporal change problems were still in 
fluencing the results, the FA method gave the most promising results. 
Five transformations were generated for this method: principal compo 
nents transformation, varimax rotation, quartimax rotation, equimax 
rotation, and oblimin rotation. Of the five, three rotations contained 
useful contrasts between the BW scene and the color scene. Transforma 
tion coefficients for the principal components and one selected rotation 
are shown in Table 1. Axis 1 of the varimax rotation was the most suc 
cessful in mapping change. An example map product is shown in Fig. 6. 
The method of density slicing the selected transformed axis into five 
levels, used in the third method, was also used in this method. In ad 
dition, histograms of the single, transformed contrasting channel data 
were used for guidelines in density slicing. 
Table 1. Transformation Coefficients 
Channels Axes: 1 
2 
3 
4 
PRINCIPAL COMPONENTS 
TRANSFORMATION 
Black-and-white 
0.1194 
-0.9927 
-0.0058 
-0.0130 
Color 1 
0.5752 
0.0806 
-0.1683 
-0.7964 
2 
0.5713 
0.0608 
0.7779 
0.2544 
3 
0.5731 
0.0653 
-0.6053 
0.5485 
VARIMAX ROTATION 
Black-and-white 
-0.07048 
1.00736 
-0.04420 
-0.14098 
Color 1 
0.35905 
-0.01958 
-1.79843 
-8.81860 
2 
0.30827 
-0.02672 
4.39597 
2.42510 
3 
0.34721 
-0.02395 
-2.56193 
6.46385