Sains Malaysiana, 2016;45:659-667.

Abstract

Band ratio combination has been proven to be one of the most useful image processing methods for lithological
discrimination, as discussed by many researchers in the past. In this study, bands from Landsat 5 TM were used to generate
different ratio combinations to discriminate the different lithologies of two islands located at the southern end of the
Langkawi archipelago, specifically the Dayang Bunting and Tuba Islands. Both islands comprise similar lithological
units – namely, limestone/marble (Permian & Silurian-Ordovician), granite and alluvium. There are two rock formations
that are limestone/marble dominated. The first is known as the Chuping Formation, which consists of limestone/marble
and the other is the Setul Formation, which consists of not only limestone/marble but also of two detrital intervals.
Different ratio combinations obtained from past researchers and that was produced from this study were tested on the
image of the Dayang Bunting and Tuba Islands to identify the best ratio combinations that were able to discriminate the
different lithologies for both islands. A total of 28 combinations were performed to examine which combinations are the
most effective. From the 28 combinations, three were identified as the most suitable; 4/3 5/2 3/1, 5/3 4/3 4/1 and 4/2 5/3
4/3 in the RGB sequence. These combinations enhanced the spectral differences of each lithology unit so that it can be
distinguished easily. Apart from the difference in the spectral response, the texture of the lithologies was also enhanced
to assist in discriminating the different units.