In book of Sutanto (1986), image interpretation is divided into 3 steps, detection, identification, and analysis. The approach conducted come through identification of tectonic landform elements such as fault, fold, and drainage pattern. Information of landform and geological structure are resulted to obtain the general description and the own relationship of lithology. Lithology identification is based on the approach through landform and geological structure interpretation. The following describes the steps of landform and geological structure interpretation.
1. Interpretation of Landform
Landform is resulted of landscape elements classification in a region which has the certain characteristics. The complex landscape unit must be broken into more simple unit which has the similar characteristics which is needed to reconstruct geology. Landform interpretation is related to geological structure because most of geological structures were resulted through landform forming processes in the past. Twidale (1971) explained that geological structure such as joint, fault, and fold can be found generally and have the significant effects to landform forming processes.
Figure 1. Structural landform
Landform interpretation can be classed into sub-units of landform which are composed of geological structures. Sub-units of landform create parameter that can be interpreted by interpretation keys such as relief and drainage pattern related too much to geological structure. In landform identification, it can be seen by the basic image interpretation keys: shape, then more complex: pattern which can show specific shapes like recurrence patterns. In landscape elements interpretation, drainage patterns can be identified based on the certain scale. Drainage pattern can be identified based on texture appearances and these are able to give information of landform in the region.
2. Interpretation of Geological Structure
Figure 2. Geological outcrop
Interpretation of geological structure applying image interpretation keys is based on color, pattern, shape, texture, and shadow. Color in image describes intensity obtained by an object so it shows the difference of dark-bright which becomes the topography difference. In geological interpretation, shape and pattern has role to produce the clear appearance such as fault, joint, and fold that have their own characteristics, texture is shown in roughness level of surface to know surface condition while shadow to give information of altitude difference on each object at surface.
Radar image with its polarization principle is used to improve the potential in interpreting geological structure patterns through lineament.