Tropical Forest Cover Typees Differntiation using Satellite
Optical and Radar Data:A Case Study From Jambi, Indonesia
Abdul Hamid Marwat Agus Wary anta Yousilf Ali Hussin
The International Institute for Aerospace Survey
And Earth Science (ITC)
7500AA, Ensched, The Netherlands
Fax (31) 53-4874-399
E-mail :HUSSIN@ITC.NL
Abstract
The capabilities of optical (Landsat TM and SPOT) and radar (JERS-1 and ERS-1) satellite images for mapping tropical cover types differentiation were compared and the relationship between some forest stand parameters and radar backscatter determined. The methodology used individual image of each optical and radar satellite were classified using computer pattern recognition and visual interpretation. It was found that SAR satellite data can add new capability to the optical images in radar to obtain more reliable cover types mapping.
Introduction
Never before in the history of mankind, have trees and forests assumed that global importance that is evident today. Forest resources are important socially, economically and environmentally, especially tropical forests which are the home of least two-thirds of the world living organisms. Forest are being destroyed at alarming rates worldwide. The increasing rate of the deforestation of tropical rain forest grave cause for concern on several counts. Habitats communities and unique system are lost before they can be studied. According to estimates there are about 1900 million hectares of tropical forest in the world, but this number is expected to decrease to 500-800 million hectares by the year2050. Scientists dealing with trees and allied subjects have come to a wise conclusion that if that we fail to conserve the remaining tree wealth and also fail to rehabilitate the deforested and degraded wastelands in as short a time possible then the every survival of both human race and wildlife will be in danger.
Indonesia has large tropical forest (about143 million hectares or 75% of the total land surface). The Indonesia Government has set the year 2000 as target to reach sustainable forest management for timber production. An urgent need exists for data on actual forest extent, forest biophysical characteristics, the process of deforestation and land cover change. Data for the verification of sustainable forest management and surveillance of forest reserves are also needed. Since 1989,Indonesia Government is doing an inventory of forest, using a combination of aerial photography and ground check. However, cloud, fog and rain can prevent acquiring useful information. To overcome this problem, the Ministry of Forest has chose satellite radar data. Radar system such as ERS-1 (European Remote Sensing Satellite), JERS-1 (Japan's Earth Resources Satellite) and Radasat has several unique advantages over optical system. These including the capability to penetrate clouds and to be operated day and night. Similarly, forest damage cannot be detected at an early stage damage detection id possible. Current conventional methods and using optical satellite images to acquire data on yearly basis largely fail due to the problems (severe cloud cover, rain ,etc.) mentioned above. The objectives of this research were: to compare between the ability of radar satellite imaging system (ERS-1 and JERS-1) and optical satellite scanning imaging system (Landsat and Spot) data to detect tropical forest cover types, and to test if there is any relationship between tropical forest characteristics (e.g.DBH,height, basal area and crown coverage) and the radar backscatter of ERS and JERS images.
Description of study area
The study area is located approximately in 01025'00" to 01045'00" Latiture South and 102015'00" to 102045'00" Longitude East ,line in jambi provience, between kota jambi and gunnug Kerinci, in Central Sumatra, Indonisia. The study area covers about 50 km * 35 km(1750km2), and comprises a mountainous nature reserve area in the west and timber concession areas in the east. Apart from th etimber concession the area also contains along Tebo, Batang Hari, and Batang Tabir rivers, " transmigration" villages, and oil palm plantation/oil palm estate.
The forest concession (HPH) has been selectively logged by PT Sylya Gama, which covers about 30.000 ha. part of concession will be clear felled to establish an Industrial Forest Plantation (HTI). Part of the forest allocated for research on forest regeneration and management, and education purposes for Faculty of Forestry, Gadjah Mada University, Yogyakarta. Forest, Rubber, oil palm, rice, Clear cut, and Water, are the main land cover types.
Materials and Methods
For the study comparison between optical and radar satellite images, remote sensing data acquired by both passive and active system were used. The optical images were from Landsat Thematic Mapper ™ and SPOT, while radar data was from ERS-1 and JERS-1SAR images. Landsat TM image acquired on 15-9-1993 has seven bands but only three bands were used for the study viz. band 3(0.63-0,69 micro meter, red), band 4(0.76-0.90 micro meter, near infrared), and band 5(1.55-1.75 micrometer, middle infrared). The spatial resolution of this image is 30m*30m.SPOT image was acquired on 05-9-1994 has three bands viz band1 (0.50-0.59 micrometer, green) band2 (0.61-0.68 micrometer, red) and band 3 (0.79-0.89 micrometer, near infrared). The JERS-1 SAR image was acquired on 16-9-1994 having L-band (23.5 cm wavelength) and incidence angle of 35 degrees. The spatial resolution is 18 meter. The ERS-1 SAR images has 30 meter resolution acquired on 08 June 1995 in C-band (5.6 cm wavelength). Other anicillary data which were used ain this research include topographic maps 1:50,000 ofo 1982 and 1:250,000 of 1982. Research methodology is illustrated in figure 1.
Figure 1: Methodology flow chart for the research
