176 
Figure 8: Landsat Principal component imagery of Sukabumi area and their interpretations 
on lithologic discriminations, a) PC-1 imagery, b) PC-1 interpretation, c) PC-2 imagery, 
d) PC-2 interpretation. 
thus, reflectance differences between rocks, soils and 
other surface materials which may result from 
compositional factors, are enhanced. Band ratioing of 
all 4 Bands MSS Landsat data is capable of forming 12 
new ratio imagery, the 5/4, 6/4, 6/5, 7/4, 7/5 7/6 and 
their reciprocals. 
Analyzing the band ratio imagery from areas in 
tropical regions, such as West Java is more delicate 
because of the vegetation density and the degree of 
weathering. Interpretation of the surface materials 
on the imagery must be conducted in more then one step 
taking into consideration various parameters such as 
the tex ture of the surface materials which leads to 
its resistivity, the degree of weathering as indicated 
by the moisture contents of the materials, the 
drainage patterns and the vegetation density. As 
examples, three Band Ratio imagery of the Sukabumi 
area consisting of the ratio image from two visible 
Band (Patio 5/4 imagery), the ratio of infrared to 
visible band imagery (7/5) and the image from the 
ratio of two infrared bands (7/6) are presented here 
fot the lithologic discrimination purposes. 
The Landsat band ratio 5/4 imagery (Figure: 9 a,b) 
shows a dark tone for the most recent volcanic 
products (Qr2) and indicates a high vegetation 
density. Other surface materials show brighter tones 
than Qr2 and are interpreted as older, more highly 
weathered, rock with low vegetation cover. Within this 
bright tone area, only the tuffaceous sandstone of the 
Bentang Fm. (Tpt) is discernable. 
Landsat Band Ratio 7/5 imagery (Figure: 9c,d,), on 
the other hand, is capable of separating Te3 from Te6. 
Thus it can distinguish an area with high vegetation 
density and high moisture content (Te3) from an area 
of low vegetation density, low moisture content and 
highly resistant rock (Te6). The ratio products 
between the infrared band and the visible band of 
Landsat digital data are capable of discriminating 
Quarternary volcanic materials by determining the 
degree of weathering and, therefore, the eruption 
event from the latest (Qr2) to the earliest (Qr4). 
Comparison of the carbonate terrain (Te7) with the 
older volcanic materials (Qr4) showed brighter tone , 
less vegetation density and coarser texture in Te7 and 
a darker tone, higher moisture content and high degree 
of weathering in the Qr4. 
Tone discriminations of Landsat band ratio 7/6 
imagery (Figure: 9e, f)show a distinct distribution 
of the volcanic materials, the Qr2 and Qr4, the 
tuffaceous sandstone (Tpt), marl of Jaitpang Formation 
(Te3) and greywacke of Rajamandala Formation (Tel). 
From its texture, the volcanic breccias (Te6)is also 
clearly delineated in this imagery. 
Comparison between these processed imagery and the 
1:100,000 scale geologic map of the Sukabumi area 
(Effendi,1974; Sukamto,1975) (Figure:10) showed that: 
1). There are lithologic contrasts for an area 
north of the Cimandiri River as to its south. The 
contrasts are indicated by their tone, texture and 
also by their disturbed drainage systems. These 
N 
indications 
the Cimandi 
volcanic br 
along the r 
2). In ge 
Quarternary