A Validation Experiment of the Reflectance Products of KOMPSAT-3A Based on RadCalNet Data and Its Applicability to Vegetation Indexing

Kwangseob Kim,Kiwon Lee

doi:10.3390/rs12233971

Abstract

Surface reflectance products obtained through the absolute atmospheric correction of multispectral satellite images are useful for precise scientific applications. For broader applications, the reflectance products computed using high-resolution images need to be validated with field measurement data. This study dealt with 2.2-m resolution Korea Multi-Purpose Satellite (KOMPSAT)-3A images with four multispectral bands, which were used to obtain top-of-atmosphere (TOA) and top-of-canopy (TOC) reflectance products. The open-source Orfeo Toolbox (OTB) extension was used to generate these products. Next, these were subsequently validated by considering three sites (i.e., Railroad Valley Playa, NV, USA (RVUS), Baotou, China (BTCN), and La Crau, France (LCFR)) in RadCalNet, as well as a calibration and validation portal for remote sensing. We conducted the validations comparing satellite image-based reflectance products and field measurement reflectance based on data sets acquired at different times. The experimental results showed that the overall trend of validation accuracy of KOPSAT-3A was well fitted in all the RadCalNet sites and that the accuracy remained quite constant. Reflectance bands showing the minimum and maximum differences between the sets of experimental data are presented in this paper. The vegetation indices (i.e., the atmospherically resistant vegetation index (ARVI) and the structure insensitive pigment index (SIPI)) and three TOC reflectance bands obtained from KOMPSAT-3A were computed as a case study and used to achieve a detailed vegetation interpretation; finally, the correspondent results were compared with those obtained from Landsat-8 images (downloaded from the Google Earth Engine (GEE)). The validation and the application scheme presented in this study can be potentially applied to the generation of analysis ready data from high-resolution satellite sensor images.

Highlights

Absolute atmospheric corrections consist of minimizing atmospheric effects in radiometric images and subsequently generating reflectance products by considering the time of acquisition of satellite images and the corresponding atmospheric conditions
Many types of high-resolution multispectral optical satellite images are currently used in the civilian and commercialized sectors. They are obtained from WorldView-2 (with a spatial resolution of 1.8 m for eight visible and near-infrared (VNIR) bands at the nadir, except panchromatic images (PAN)) and WorldView-3 (with a spatial resolution of 1.24 m for eight VNIR bands and 3.7 m for eight shortwave infrared (SWIR) bands except PAN) by DigitalGlobe, Pleiades-1A/1B by the Centre National d’Études Spatiales (CNES), Gaofen-9 by the Chinese Academy of Space Technology, and Korea Multi-Purpose Satellite (KOMPSAT)-3 [5]
Atmospheric correction has been widely studied in satellite remote sensing, it is still being researched and developed because of its practical importance in increasing data value for further scientific applications

Summary

Introduction

Absolute atmospheric corrections consist of minimizing atmospheric effects in radiometric images and subsequently generating reflectance products by considering the time of acquisition of satellite images and the corresponding atmospheric conditions. Many types of high-resolution multispectral optical satellite images are currently used in the civilian and commercialized sectors They are obtained from WorldView-2 (with a spatial resolution of 1.8 m for eight visible and near-infrared (VNIR) bands at the nadir, except panchromatic images (PAN)) and WorldView-3 (with a spatial resolution of 1.24 m for eight VNIR bands and 3.7 m for eight shortwave infrared (SWIR) bands except PAN) by DigitalGlobe, Pleiades-1A/1B (with a spatial resolution of 2.80 m and four bands, except PAN) by the Centre National d’Études Spatiales (CNES), Gaofen-9 (with a spatial resolution of 3.20 m and four bands, except PAN) by the Chinese Academy of Space Technology, and KOMPSAT-3 (with a spatial resolution of 2.80 m and four bands, except PAN) [5]. TOC reflectance products correspond to surface or bottom-of-atmosphere reflectance products

Results

Discussion

Conclusion