Studies on Interpretation and Orientation of the Damaged Pine Forests by Pine Caterpillars with Airborne Video Techniques

The research work of using the techniques of airborne video to distinguish and orientate the damaged pine forests by pine caterpillars was conducted at three plots in Wuming County, Guangxi Zhuang Autonomous Region during December 1995 and April 1996.The high quality images whose ground resolutions were 2.01m, 1.50m, 1.01m and 0.50m were acquired by using a motor glider of a 3 seated airplane, GPS equipment, a video camera and video recorder. The image was processed by capturing the individual video frame, mosaicing the flight line frame pairs, preparing the ortho photoquad, selecting ground control points and warping the imagery to the ortho photoquad, and adjusting the contrast of the displayed brightness values of digital image with MIPS software (version 3.3) running on DOS environment in laboratory. The efficiency of processing image was improved by using auto capture function of MIPS to capture individual video frames and using the auto correlation feature of image to assist placing the tie point and mosaic the frame pairs.A satisfied result of warping image was reached by using the distinct ground characters as the ground control points (GCPS) to warp image.The results of warping image were not satisfactory in large area of forests, when 6 GCPS were failed to be found, and the main reason was the aircraft sensor had not been used.Two methods were used to adjust the image contrast, and the image information of damaged forests was stressed.The result also showed the damaged degree of pine forests was divided into 3 levels, that is over 90%, 90%～75% and 75%～50% of defoliation respectively.The damaged areas were precisely oriented by using distinct ground characters as GCPS to warp imagery. When the large forest area was monitored with the airborne video techniques, and much better distinction effect and higher orientation precision were needed, the GPS base station and the aircraft sensor are needed to be used.