International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004 
object in the image. We simply recognize objects, such as a 
house, tree, or road, then knowing their size, we can figure out 
the dimensions of other objects in the same image and 
recognize the extent or coverage of the entire image. 
Color and color tones constitute textures of features. Texture 
describes the structure of the variation in brightness within an 
object as well. Vegetation and water in certain spectral bands 
may have the same mean brightness, but they may have 
different textures. Therefore, they can be differentiated using 
the texture knowledge of vegetation and water. 
Finally, color and color tones also show shadows. Shadows can 
be used to figure out topography and geomorphology, i.e., 
heights of features and mountain ridges and directions of plate 
tilts. For instance, the image in Figure 5 that shows topography 
and geomorphology was created by shading the DEM data in 
Figure 4 (Idrisi, 1997). 
A set of rules that allow analysis of the terrain based on color 
and color tone, among other factors, was developed 
(Demirkesen, 2001) and used in this study. Such rules provide 
the foundation for an automated system to aid image analysis 
and scene understanding. 
  
Figure 3. False color compsite image RGB=743 
with overlaid stream drainage patterns 
2.2 Stream drainage patterns 
Geomorphologists dealing with remote sensing applications 
have studied stream drainage patterns and their relationships to 
terrain conditions. Many have deduced different rock properties 
and structures using topographic relief interpretation from the 
imagery. They have illustrated and quantified relationships 
among selected rock properties, topographic relief, and stream 
drainage patterns (Drury, 2001; Konecny, 2002; Lillesand and 
Kiefer, 1994; Pandey, 1987; Prost, 1994; Ray, 1960). 
Stream drainage density in eroding rock landscapes can be 
explained by a function of rock resistance to weathering, 
topography and climate. Rock resistance to both chemical and 
mechanical weathering is an important factor in explaining 
drainage patterns. In terms of topography, higher relief creates 
a finer-textured drainage as in our study image. But the 
relationship with climate is more complicated. It is the amount 
of protective vegetation cover, which can be correlated to 
temperature and precipitation, that significantly controls 
erosion and drainage density. Thus softer rocks, such as shale 
areas, have higher drainage densities in drier climates than 
wetter climates. The protection of the rock and soil surface by 
vegetation compensates for the increase in precipitation. 
Stream drainage density usually indicates the porosity and 
permeability of the underlying materials. Materials with good 
permeability generally have a medium to coarse drainage 
density. Such materials include sandstones, terrace gravels, 
limestones, volcanic ashes, and sand dunes. 
Stream drainage density also shows that fine-grained or 
impermeable materials have little moisture on the surface. This 
moisture does not infiltrate and must run off on the surface. 
This causes a dense integrated drainage network. Shales, fine- 
grained volcanic ashes, mudflats, and igneous and metamorphic 
rocks that weather to clays (e,g., gabbros, serpentinities, schists, 
slate and highly altered granitic rocks) usually have fine- 
textured drainage patterns 
Stream drainage patterns can reveal larger-scale coarse 
structure of underlying rocks, e.g., stream drainage patterns 
with numerous straight parallel or sub-parallel segments can 
indicate extensive jointing on dipping bedded or foliated rocks. 
Consistent angular relationships between stream elements 
indicate fractures. Co-centric drainage shows doming of layered 
sequence of rock related to intrusion or folding. Radial drainage 
shows doming, volcanic activity, Or small resistant cylindrical 
intrusions in less resistant rocks. Well-developed dendritic 
drainage patterns (as in our study image) without well- 
developed parallel elements suggest à uniform stratum without 
abundant discontinuities. This can consist of sedimentary, 
igneous, or metamorphic rocks, or sheets of relatively uniform 
glacial or alluvial materials. Distributed channel patterns 
indicate alluvial fans, pediments, or deltas, and they are usually 
associated with an abrupt decrease in stream velocity. 
Extensive drainage channels indicate strong foliation, dipping 
sequences of resistant and nonresistant rocks, or strong 
unidirectional fracturing. 
The shapes of the main channels in the stream drainage area 
also provide clues about the geological structures. For instance, 
braided channels indicate easily erodible coarse-grained 
materials, while meandering channels indicate medium to fine- 
grained materials. Relatively narrow and straight channels 
indicate resistant materials, but abrupt changes in channels 
indicate changes in geological structures. Extreme changes IN 
channel types indicate changes in the materials that make up the 
bank. The main channel in the drainage area having 
discontinuities indicates cracks (breaks and fractures) and/or 
faults, as well as unconformities. 
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