ing and 
distortion caused by the effects of layover and the low 
incidence angle of the ERS-1 radar. The integration 
of the ERS-1 radar with the Landsat TM image 
clearly provides the perception of moderate terrain 
relief in the forest-covered and scarcely-forested 
areas. 
The Landsat TM 432/RGB image was then 
merged with the August 1993 ERS-1 data set. The 
Mapanuepe Lake appears black indicating specular 
reflection and low backscatter coming from the 
smooth water surface. In the merged data using the 
July 1993 ERS-1 SAR data, this lake appears light 
gray because of strong wind effects prevailing in the 
area at the time of image acquisition. In both merged 
data sets, areas of high relief can be clearly detected 
from the floodplain, and built-up areas such as the 
towns of San Marcelino and Castillejos have a bright 
white appearance caused by the strong backscatter of 
corner reflectors (Figure 6). 
80 CONCLUSION 
ERS-1 SAR imagery may show active lahar. 
The main physical parameters that must be 
considered are surface roughness, image texture and 
morphology. While at this stage it seems difficult to 
confidently map lahar boundaries in detail, radar 
imagery including ERS-1 SAR data will play a major 
role in monitoring changes because of its all-weather 
sensing capability. These radar data will be 
particularly useful over the Mount Pinatubo area 
during the worst weather conditions in the typhoon 
season when lahars are most destructive and cloud 
cover adversely affects sensors using the visible- 
infrared portions of the electromagnetic spectrum. 
Radar imaging of the lahar-affected areas will provide 
updated information to disaster controllers, 
rehabilitation planners and decision-makers. 
ACKNOWLEDGMENT 
The funds and satellite imageries used in this 
study have been provided by the European 
Commission and the European Space Agency through 
the EC-ASEAN ERS-1 Radar Research Pilot Projects. 
The authors gratefully acknowledge this support as 
well as the various training components of the project 
conducted in the ASEAN countries, the Laboratoire 
de Geologie-Geomorphologie ^ Structurale et 
Teledetection of the Universite Pierre et Marie Curie 
In Paris, France, and ESA-ESRIN in Frascati, Italy. 
The authors also wish to acknowledge the 
full Support extended to the pilot project team by 
Director Virgilio S. Santos of the National Remote 
447 
Sensing Center of NAMRIA and Philippine National 
Representative to the EC-ASEAN Advisory Board. 
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