Using ALOS data for classification of land and water use in Nha Trang, Viet Nam

Abstract

The increasing availability of Earth observing satellites and instrumentation leads to increased image quality and quantity. The Advanced Land Observation Satellite (ALOS) provides three instruments: (1) Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM – 2.5m resolution), (2) Advanced Visible and Near Infrared Radiometer (AVNIR-2 – 10m) and (3) Phased Array type L-band Synthetic Aperture Radar (PALSAR – 2.5-10m). These instruments all provide improved opportunities for systematic land and water-use classification in coastal regions. This study concentrates on the vicinity of Nha Trang City, Vietnam. We use atmospherically corrected ALOS AVNIR-2 data for supervised classification of land and water use. A hierarchical classification approach is used separating inland and coastal as well open water use types. On the land surface, land cover such as urban, cultivated land and aquaculture represented 10.1, 4.9 and 3.0% of total of land use, respectively. In the coastal and open water regions, eight ports and anchoring sites were located within semi-open waters, river mouths and nearby human settlements on islands. Also 23ha of marine culture was identified around Hon Mieu, northwestern Hon Mot and southern Hon Tre. Even though high spatial resolution ALOS AVNIR-2 data was used, some land cover types such as small houses, were difficult to identify. In addition, spectral similarities were found in marine culture cages and ships. Spectral similarities were resolved using a fusion technique or insitu identification of these special types of land cover and water use. In general, the typical length scale (spatial, spectral) of ALOS AVNIR-2 data was sufficient to classify land cover and water use in a coastal region of Vietnam.