Simplified and Robust Surface Reflectance Estimation Method (SREM)

What is it about?

A new Simplified and Robust Surface Reflectance Estimation Method (SREM) is developed based on the Satellite Signal in the Solar Spectrum (6SV) radiative transfer (RT) model equations, without integrating information on aerosol particles and atmospheric gases. The SREM surface reflectance (SR) retrievals were validated against in situ measurements collected by an Analytical Spectral Devices (ASD) spectrometer, and cross-compared with Landsat (LEDAPS and LaSRC) SR products for diverse land surfaces and varying atmospheric conditions, as well as tested on Sentinel2A and MODIS data products. This study concluded that the SREM is capable of accurately estimating spectral surface reflectance (SR) without incorporating information on aerosol particles and atmospheric parameters, and the SR retrievals are comparable with the SR data collected by the ASD spectrometer as well as those provided by Landsat SR products (LEDAPS and LaSRC) which use the 6SV model. Larger positive values of MBE were observed for coastal aerosol band compared to longer wavelengths, which may be related to increase scattering effects at lower wavelengths. Large negative values of MBE were observed in SREM from green to SWIR2 bands when compared to Landsat, which were mainly due to “under-correction (lack of atmospheric correction)” of data by the Landsat atmospheric correction algorithms when compared to TOA reflectance. The preliminary analysis implies that SREM has a strong potential for augmenting vegetation and crop monitoring and it can be implemented with Sentinel-2A and MODIS data or other multispectral satellite data sets.

Featured Image

Why is it important?

Advantages of SREM: 1. SREM is the simplest method compared to the existing surface reflectance (SR) estimation methods. 2. SREM performs SR inversion based on the 6S Radiative Transfer Model (RTM) equations. 3. SREM does not depend on RTM simulation and a comprehensive lookup table (LUT). 4. SREM does not use the following parameters: a. aerosol optical depth (AOD), b. aerosol model, c. water vapor concentration, d. ozone concertation, and e. other gases. 5. SREM can provide SR retrievals over diverse land surfaces including urban, vegetated, and desert surfaces. 6. SREM SR values are comparable with the following satellite SR products: a. Landsat SR product (LEDAPS & LaSRC) at 30 m resolution, b. Sentinel-2A SR product at 10 m resolution, c. MODIS (MOD09) SR product at 500 m resolution, and d. Planet satellite at 3 m resolution. 7. SREM can be applied to other Multispectral as well as Hyperspectral satellite data. SREM ENVI/IDL CODE: SREM IDL codes for Multispectral and Hyperspectral satellite data are available on demand, please email me at muhammad.bilal@connect.polyu.hk with the subject “SREM_SatelliteName_Code” if anyone is interested, and please provide the following information: a. Full name, b. Position, c. Affiliation, d. Research application.