Digital, image processing of
Landsat MSS data for identified, geomorphic, litho logical and structural,
features in P.I.Shiresh Satpuli area of Garhwal Himalaya, India
Sayed Ahmad Ali, Liagat
A.K. Rao Department of Geology, Aligarh Muslim University, Aligarh 202002 Abstract Landsat MSS data is digitally enhanced through VAX 11/180 computer system using VIPS-32, software with a view to select appropriate band combination and spatial filtering functions for delineating certain geomorphic, litho logical and structural features. Among the various enhancement technique of digital image processing it has been observed that the band in his 4/5, 5/1 and 4/1 are useful for delineating broad litho logical, structural elements, flood pains, pediment zone with alluvial fans and perennial streams. FCC of brightness index shows that it is good for drainage studies. The principal component analysis, PC1 and PC3 are good for interpretation of regional structure whereas PC2 proved good for geomorphic studies. It has also been observed that the directional filtering using SOBEL operators is good for delineating lineaments and good fractures. Introduction The present study area which forms a part of sub-Himalaya and Lesser Himalaya is bounded by latitude 29°50' to 30°15' and longitude 79915' to 78°40' E, covering an are of about 1322 sq. km., was selected as tost site for digital image processing. The analysis of the enhanced images after applying various functions were carried out by visual interpretation method using tonal and textural contrast. An attempt has been made to delineate geomorphologic, litho logical and structural features from digitally enhanced images and correlate them with field data. Geological set up Geologically, this study area may be divided into three broad zones each of which is separated by a major thrust. The southern part of the area is occupied by siwalik belt, whose fringing zone is occupied recent alluvium. The central portion of the area is occupied by Karol Belt which is separated from the Siwaliks by the Main Boundary thrust, whereas the chail Group belonging to Kumaun Super group is exposed on the north of the area (Fuche and Sinha 978). The two thrusts that separated the three geological untis are Main Boundary Thrust of the Himalaya on the south name and Garhwal thrust on the north. These thrust zones trend more or less in HW-SE direction almost parallel to that of the Himalaya Trend. The two major rivers of this area, viz. the Ganga and Hayar cut across there thrusts by at some places their sources appear to have been affects by these thrusts. A generalized stratigrapchic sequence of different litho units and their litho-characters encountered in teh area are given (after, Kumar and Dhaundiyal, 1979, Gairola 1980) in Table 1 and shown in Fig. 2.
Methodology Digital image processing of Landsat BSS data stored in the form of computer compatible tape (Data of pass: 27.11.83; Path-row: (D146-039) of the parts of study area (Pixel No: 18co-2312; Scan line no 1150-1662) has been carried out on Super mini computer VAX 11/780 using VIPS-32 software. Pericolor-2001 display of the images. The selected enhanced images used for display of the images. The selected enhanced images was received on film negatives recorded by using the Dunn Camera connected directly processed in the photo-laboratory to produce a hard copy for visual interpretation. Interpretation was competed with help of the survey of India toposheets, existing geological and geopmorphological map and field data. The following image functions of VIPS-32, software package have been used for generating various types of enhanced images.
CRAT: The Landsat MSS data were rationed to criminate the extraneous effects like clouds and shadows because they changes the reflectance value. The following ration combinations were carried out to produce a composite color ration image.
KLOEVE: Principal component analysis was carried out by applying various principal component transformations. The products of combination of PC1, PC2 and PC3. were analysed visually. Ti was found that n addition to the broad lithological discrimination; geomorphic variation, drainage patterns and parallel lineaments have come up picely. These lineaments are not only closely related with the thrusts and lineaments are faults interpretation aerial photos and imagery but a few more new lineaments were also picked up indicating the presence of other thrust slices. PC1 and PC3 are very good for analysis of regional structure whereas PC2 is proved good for geomorphic studies especially the study of drainage pattern. Combinations of Band functions Functions like CRAT-KLOEVE were also carried out using ratio 5/7, PC1 and PC2 and was found suitable for demarketing major and minor lineaments. Broad litho logical discrimination between siwalik group and pre-territories, geomorphic units like flood plain, piedmont zone and geomorphic features like alluvial fan were also picked up in this FCC. Directional Filtering Laplacian was applied in band 7 but it did not exploits good results and was found unsuitable for geological studies. SOBEL operator was applied in band.7. It was found very useful for lineament study because it has a capacity to enhance the image features, in a particular direction on the basis of matrix/ matrix number 7,8 and 9 were applied for present study. It was found that SOBEL-7 enhanced the NE-SW trending the lineaments, SOBEL-9 enhances the lineaments trending in NW-SE direction. Edge Enhancement Enhancement product exhibits drainage liens with some geomorphic and structural elements. Edge extraction in particulars bands like 7 and 5 were also applied which gives only a better contrast in the image. Conclusion
The authors express there thanks to Prof. S.N. Casshyap, Chairman, Department of Geology, Aligrah Muslim University, Aligarh, for providing facilities. Thanks are due to Prof. S.H. University, Aligarh for going through the manuscript. Reference
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