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Mapping
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A Comparison between ERS-1, JERS-1, and Radarsat Satellite Radar Images for Mapping Tropical Deforestation
2. Material and Methods
2.1 Study area
The study are of this research is located in Jambi Province, between Jambi and Gunug Kerinci, new settlement and timber concession (System Gama Concession) areas in the east. The area is roughly 50 x 30 km in size, its latitude is between 1-2 degrees south and its longitude is between 101-103 degrees east. The forest (HP), Conversion Forest (HPK), and other Land Use (APL), then land cover of the study area are Unproductive dryland (lktp), Agriculture (Ptn), and Lowland forest (Hr).
2.2 Material Used
2.2.1 Remotely Sensed Data
The following remotely sensed data were used in this research: ERS-1 Synthetic Aperture Radar (SAR), Multi-temporal (4 image), data acquired on March 21, 1993, October 17, 1993, June 6, 1994, and July 7, 1994, in C-band (5.5 cm wavelength), 23 degree incidence and VV polarization; JERS-1 Synthetic Aperture Radar (SAR) of August 16, 1994, in L-band (23.5 cm wavelength), 35 degree incidence and HH polarization; Radarsat Synthetic Aperture Radar (SAR) image of August 17, 1996 is a C-band (5.6 cm wavelength), normal angel of 40 degree and HH polarization.
2.2.2 Other Ancillary Data
the following maps were used in this research: topographic map of study area at scale 1:50.000 and 1:250.000; Consensus of Forest Land Use map (TGHK map) of study area at scale 1:250.000; forest vegetation and land cover map of study area at scale 1:250.000; soil and agro-climatic zone map of study area at scale 1:200.000 or 1:250.000; transmigration and agriculture development area map at scale 1:200.000 or 1:250.000; and road network and drainage (river) map of study area at scale 1:50.000 or 1:250.000.
2.3 Methodology
The outline of the general methodology of the research is shown in Figure 1.
Figure 1 The general research methodology
2.3.1 Image Verification and Image Restoration
The removal of speckle noise can be attained by overlaying of several looks of the same area and averaging out the speckle values, or by the use of non linear filter such as the Lee filter , or Majority filter. Geometric correction is done using ground control points (GCP) from the digital topographic map or topographic map, or digital road network and river map as the master map and the radar imagery as the slave map. The minimum number of GCP are 4, more is better, and the sigma value should be less than 0.3.
2.3.2 Image Processing
The real processing of the image in this research are image enhancement, image classification and the accuracy assessment of the classify image. The image enhancement methods used were contrast manipulation (with contrast stretching; liner stretching and histogram equalization) and multi image manipulation (with principal component analysis). Before run classification, the signature area is indicated based on the various types of target and their appearance in the radar image, also some information about the research area (information from the orthophoto or another sources were used too). Then supervised classification was used. The accuracy assessment is expressed by performing the classification error matrix (confusion Matrix or contingency Table) and evaluating them.
2.3.3 Visual Interpretation and Samples Verification
The simple approach for classification of radar is to examine then visually, using a hard copy image. he visual interpretation was carried out based on tone/colour, texture, pattern, and association. The end result of the visual interpretation lead to the interpretation key. Then, the visual interpretation maps of radar images will be digitized, polygonized, and rasterized in 12,5 pixel size (or less) to get more information about the field situation and to establish the correlation between the classification and the real situation in the field, in the order to improve the accuracy of the interpretation and classification.
2.3.4 Geographic Information system (GIS) analysis
The information from remotely sensed data were to be integrated using GIS. Also it will integrate TGHK map, slope map. Soil type and agro-climatic map. GIS as a tool to overlay and analysis and other important about the study area.
Results
Because the authors just came back from the field work and still running the analysis, given the due data of submitting this manuscript, it was difficult to present results in this paper. However, hopefully during the conference, the authors will present s the results and a handouts to the conference attenders.
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