Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986 
Synthetic geological map obtained by remote sensing 
An application to Palawan Island 
F.Bénard & C.Muller 
Institut Français du Pétrole, Rueil-Malmaison, France 
ABSTRACT: This project was undertaken to compensate for the lack of new data for the blanks of maps and to 
link spot datings due to bad outcrops on Palawan Island. A synthetic map of all the available data, including 
new field work and datings, is based on remote-sensed documents. Good results were obtained using 
black-and-white prints of Landsat MSS (band 7). Faults N60E on the E. coast show a recent normal movement, 
and the sinistral movement of the meridian zones is confirmed by field work. The geological units shown on 
the preexisting maps are identified and separated into subunits characterized on remote-sensed documents by 
their morphology - texture - tone properties. These subunits are superimposed on the geological units. This 
map suggests new hypotheses for further investigations on both the tectonic and lithological aspects. 
RESUME : Cette étude a été entreprise pour pallier le manque de données récentes, les lacunes des cartes et 
pour uniformiser les datations rendues ponctuelles par les difficultés d'affleurement de l'Ile de Palawan. 
Une carte synthétique, s'appuyant sur les données de télédétection homogénéise les données préexistantes et 
inclue les résultats de travaux de terrain récents accompagnés de nouvelles datations. Des images noir et 
blanc de Landsat MSS (bande 7). L'interprétation, visuelle sur agrandissements au 1/500 000 s'appuie 
essentiellement sur la morphologie. Deux directions majeures ressortent : l'une à N60 avec un mouvement normal 
récent sur la côte Est ; l'autre méridienne de jeu senestre récent confirmé sur le terrain. Pour chaque unité 
lithologique cartographiée, des figurés représentent les zones caractérisées, sur images, par leur homogénéité 
en morphologie, texture, teinte, reflet de variations lithologiques. Cette carte récente suggère de nouvelles 
hypothèses pour les études ultérieures tant eh tectonique qu'en lithologie. 
INTRODUCTION 
This study is part of the "Geodynamics of SE Asia" 
program undertaken several years ago by the Institut 
Français du Pétrole. The aim of remote-sensing 
interpretation is to obtain more geological and 
structural information by using this method in 
regions covered by dense vegetation, difficult of 
access to the field, and to supplement field 
observations which have been more or less restricted 
to coastal regions. Revised age determinations of 
sedimentary sequences are based on investigations of 
calcareous nannoplankton. 
Palawan (Fig. 1) is a narrow elongated SW-NE 
trending island (about 470 km long) which is part of 
the Philippines Archipelago. It is bounded to the 
north by the South China Sea and to the south by the 
Sulu Sea. The island is predominately mountainous 
reaching its greatest altitude at 1953 m (Cleopatra 
Needle). The slopes of the mountain ranges are 
narrow and steeper to the NW, reflecting the 
asymmetry related to NW vergent overthrusts. 
Located in an equatorial zone, it is covered by 
dense vegetation and rocks undergo strong 
alteration. MSS data are the only remotely-sensed 
information available for Palawan island. It can be 
shown that good results are obtained with careful 
physiographic studies. The geological map is a 
synthesis of remote-sensing interpretation combined 
with previous data from the literature mainly L. 
Fricaud, 1984 and field survey, J. Letouzey, 1985. 
This island is covered by three Landsat images 
(number 125-52, 125-53, 126-54). Sets from 
different dates were used (see references). Due to 
cloudy and hazy conditions, only band 7 gave useful 
information. Swath number 29 (center 10'36 lat, 
119°42 long) taken by the synthetic aperture radar 
on board the SIRA shuttle was also studied. It 
covers a narrow transect of the island south of 
Mount Capoas. 
1 METHODOLOGY 
All geological and structural information was 
reported on transparent overlays placed on black and 
white prints. The same method can be applied to MSS 
and radar images, even if the elements detected are 
different in each case (Floyd and Sabins, 1983). 
Particular attention was paid to physiographic 
elements. Exemples given in Fig. 2 demonstrate how 
this kind of information extracted from satellite 
imagery can be interpreted in terms of geology. 
Results are compiled on a 1:500 000 scale map with 
Lambert Conformal Conic Projection (0NC number 
L 11). To minimize difficulties related to dense 
vegetation in these tropical areas, attempts have 
been made to recognize "photofacies" representing a 
homogenous area on remotely sensed documents. It is 
characterized by specific criteria such as 
elevation, drainage pattern, landforms, texture, 
tone, etc. These characteristics are the results of 
interaction between lithology, tectonics, elevation 
and vegetation. 
On a first map all photofacies recognized were 
represented. Some of their characteristics may 
provide information on the lithology (hard or soft, 
bedded, heterogeneous, etc.). By comparing this 
document with other available geological data from 
the literature and field work, it was possible to 
compile the synthetic geological map on which the 
main sample locations are also shown. Accurate 
geological boundaries can be drawn if there is a 
possible correlation between the "photofacies" 
detected and a geological unit having a known 
lithology. This comparison with given data is 
important for interpreting the photofacies 
characteristics (hardness, structural fabrics). If 
two formations are different in age but similar in 
lithology, they have a same "photofacies". In this 
case, formation boundaries from previous maps are 
shown as dotted lines. However, such problems can 
be solved only by detailed field work.