Abstract
The adjacency effect and non-uniform responses complicate the precise delimitation of the surface support of remote sensing data and their derived products. Thus, modeling spatial response characteristics (SRCs) prior to using remote sensing information has become important. A point spread function (PSF) is typically used to describe the SRCs of the observation cells from remote sensors and is always estimated in a laboratory before the sensor is launched. However, research on the SRCs of high-order remote sensing products derived from the observations remains insufficient, which is an obstacle to converting between multi-scale remote sensing products and validating coarse-resolution products. This study proposed a method that combines simulation and validation to establish SRC models of coarse-resolution albedo products. Two series of commonly used 500-m/1-km resolution albedo products, which are derived from Moderate Resolution Imaging Spectroradiometer (MODIS) reflectance data, were investigated using 30-m albedo products that provide the required sub-pixel information. The analysis proves that the size of the surface support of each albedo pixel is larger than the nominal resolution of the pixel and that the response weight is non-uniformly distributed, with an elliptical Gaussian shape. The proposed methodology is generic and applicable for analyzing the SRCs of other advanced remote sensing products.
Highlights
Because of the high quality and global coverage, Moderate Resolution Imaging Spectroradiometer (MODIS) products have been extensively applied in quantitative remote sensing research and have established a benchmark for Earth observation in the last two decades
The main objective of this study is to model the spatial responses of coarse-resolution albedo products derived from MODIS data, which is an important issue for many studies, such as the validation of remote sensing products and multi-scale data fusion
We have simulated the point spread function (PSF) model to describe the spatial response characteristics (SRCs) of two series of commonly used coarse-resolution albedo products derived from MODIS reflectance data over the Heihe River Basin in northwest China
Summary
Because of the high quality and global coverage, Moderate Resolution Imaging Spectroradiometer (MODIS) products have been extensively applied in quantitative remote sensing research and have established a benchmark for Earth observation in the last two decades. The width of the ground-projected instantaneous fields of view (GIFOVs) of MODIS observations vary in a complex manner, which is the comprehensive result of a whiskbroom scan imaging system and gridded sampling process [1]. This misconception causes a mismatch between the signal and its ground source and introduces error into the utilization and validation of MODIS products, for mixed pixels that cover heterogeneous areas. The first factor is the variation in the view zenith angles (VZAs) of MODIS detectors during the scanning process. Et al [4] estimated that the width of the GIFOV of the observation cells reaches approximately 2.0 times the nadir resolution in the track direction and 4.8 times in the scan direction at the scan end (the bowtie effect)
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