Conterminous United States Landsat-8 top of atmosphere and surface reflectance tasseled cap transformation coefficients

Abstract

The tasseled cap transformation (TCT) has been widely used to decompose satellite multi-spectral information into “brightness”, “greenness”, and “wetness” components. Published TCT coefficients for the Landsat sensor series have mainly been derived using top of atmosphere (TOA) reflectance and sparse data sets. Studies to derive TCT coefficients for Landsat surface reflectance (SR) are lacking. In this study, the TCT coefficients were derived independently for Landsat-8 Operational Land Imager (OLI) SR and TOA reflectance using the Gram-Schmidt orthogonalization (GSO) method. To ensure that the derived TCT coefficients are robust and broadly applicable, representative samples of soil, vegetation, and water were selected from summer and autumn Landsat-8 OLI Analysis Ready Data (ARD) sampled from 40.4 million 30 m pixel locations across the conterminous United States (CONUS). Given that the blue band is susceptible to atmospheric contamination due to its shorter wavelength, two groups of TCT coefficients were derived: one from 6 bands (Blue, Green, Red, NIR, SWIR1, SWIR2) and one from 5 bands without the blue band. As TCT results cannot be validated in a formal way, the TCT components for CONUS summer TOA and SR composites were generated and compared with National Land Cover Database (NLCD) land cover classes to provide a synoptic assessment and provide confidence in the results. In addition, three ARD tiles selected to encompass a mix of land cover types, predominantly, desert in Nevada, wetland and urban in Florida, and agriculture in North Dakota, were used to analyze the seasonal variation of the TCT components. The results demonstrate that the derived Landsat-8 TCT coefficients can effectively characterize brightness, greenness, and wetness components across the CONUS, and show good consistency for discrimination of land cover types and track seasonal surface variations. There was no significant difference between each TCT component derived using the 6-band and 5-band TCT coefficients considering a large sample of CONUS pixels. Therefore, the 5-band TCT coefficients provided in this study are recommended for use, as the blue band is atmospherically sensitive and difficult to atmospherically correct reliably.