RED EDGE BAND EFFECT ON ESTIMATING LEAF AREA INDEX IN TREE CANOPY

초록

Leaf Area Index (LAI) is one of important biophysical parameters used in agriculture, forestry, ecology, hydrology and meteorology. Remote sensing estimation of LAI has been primarily relied on the relationship between canopy reflectance and LAI. Spectral indices, such as normalized difference vegetation index (NDVI) has been known to have positive correlation with LAI and have been widely used to estimate LAI over wide geographical area. Several studies have reported the saturation problem of canopy reflectance in high LAI, in which canopy reflectance or NDVI does not show the positive correlation under highly dense canopy situations. This study was designed to find alternative spectral region to solve this problem. The red edge band refers to the wavelength region where the spectral reflectance of vegetation increases between 680 nm and 750 nm, as the middle region between red and NIR wavelength. Red edge spectral region has been known to be useful to deliver additional information regarding vegetation characteristics. In recent years, there are a few satellite multispectral sensors that comprise red edge band. The RapidEye and WorldView-2 multispectral satellites contain a red edge band while the Sentinel-2A satellite has two or more red-edge bands of rather narrower spectral region. There were several studies showing that red edge band was useful to enhance the relationship with leaf chlorophyll concentration, vegetation stress and to classify vegetation types. In estimating LAI of several agricultural crops, red edge band was helpful to improve the relationship.