The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beijing 2008 
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Chittagong using JERS-1 SAR data (Rahman and Sumantyo, 
2007) and the study separated forest, degraded forest, shrubs, 
coastal plantations, agriculture, shrimp-farms, urban and water. 
Recently L-band ALOS PALSAR data become available and it 
is useful to investigate their potential for land and forest cover 
mapping in different terrestrial ecosystems. The objective of 
this investigation was to examine this newly available data-set 
for forest cover mapping in the tropical forest regions of South 
eastern Bangladesh. 
2. MATERIALS AND METHODS 
2,1 Descriptions of Study Area 
The study area was located between 2l°29' to 21°40 / N and 
92°01 / to 92° 10' E (Figure 1) in South-eastern Bangladesh 
and distributed over approximately 300 sq. km. Sub-tropical 
monsoon climate prevails in the study region and has three 
distinct seasons: pre-monsoon hot season (March-May), rainy 
monsoon season (June-October) and cool dry winter 
(November-February). Monsoon usually accounts for about 
80% of average annual rainfall in the region. 
Figure 2. Tropical wet evergreen and semi-evergreen forest of 
the study area (photograph was acquired during 2002-2003) 
Figure 1. Location of the study area 
he forests in the region are classified as tropical wet ever-green 
and semi-evergreen forests (Champion et al., 1965, Figure 2). 
Evergreen stratum is characterized with Dipterocarpus species. 
Sometimes a certain proportion of deciduous trees are also 
present in the upper canopy of the forests. Gregarious formation 
of Dipterocarpus species is also noticed in some places with the 
rare occurrence of any other species. Bamboo appears in several 
places where upper canopy is removed, but is absent in the 
virgin forests where cane and palms are the main woody 
monocotyledons (Khan, 1979). 
2.2 Data Sets 
ALOS PALSAR polarimetric data on 9 March 2007 was used in 
the study. The data has four different modes: HH, HV, VH and 
VV polarization (Table 1). Landsat Enhanced Thematic Mapper 
Plus (ETM+) of 136/045 (path/row) on 19 December 1999 
assisted the interpretation procedure. Digital elevation model 
(DEM) of Shuttle Radar Topographic Mission (SRTM) data 
was used to ortho-rectify ALOS PALSAR data. 
Incidence 
angle 
Polarization 
Explanation 
21.5° 
HH 
• Horizontally polarized 
transmission 
• Antenna only received 
horizontal polarization 
HV 
• Horizontally polarized 
transmission 
• Antenna only received 
vertical polarization 
VH 
• Vertically polarized 
transmission 
• Antenna only received 
horizontal polarization 
VV 
• Vertically polarized 
transmission 
• Antenna only received 
vertical polarization 
Due to extreme human interference virgin forests are seldom 
noticed. Most of the crops are secondary re-growth and still in 
the process of succession to climax evergreen type. The process 
of succession is often hindered by human disturbance and thus 
leads to scrubby forests in many locations (Khan, 1979). 
Table 1. The characteristics of data-sets 
2.3 Methodology 
ALOS PALSAR image (level 1.5) was ortho-rectified using 
SRTM digital elevation data and image header information. The 
study area was separated as subset. Geometric distortion on the 
image was further checked and corrected (only single-order) 
with the ortho-rectified Landsat ETM+ image, which was 
earlier verified on the ground. Speckles on the PALSAR image 
was reduced by 3X3 Lee-sigma filtering.