Application of Normalized Different Vegetation Index (NDVI) Method to Identify Thermal Anomaly Area from Remote Sensing

Abstract

Normalized Different Vegetation Index (NDVI) is calculated from satellite image, i.e. the visible and near-infrared bands where sun rays are reflected by vegetation. Healthy vegetation absorbs most of the visible light, and reflects a high portion of the near-infrared light. Unhealthy or sparse vegetation reflects more visible light and less near-infrared light. In geothermal area, the occurrence of thermal manifestation often causes the vegetation stress due to acid fluid or high temperature. By mapping the area with low NDVI value that indicates vegetation stress, the potential area of manifestation, even for concealed features, may be delineated. Case studies in several volcanic high terrain geothermal areas show that NDVI can assist early identification of thermal manifestation area, guiding the geothermal area selection. However interpretation of the cause of low NDVI value must consider the concept of geothermal system and the man-made feature that can lead to misinterpretation.