Spectral calibration method of the field spectrometer using combined solar Fraunhofer lines and atmospheric absorption characteristics: case study at the Baotou RadCalNet site and implications for reflectance measurement

Accurate spectral parameters are fundamental for the quantitative application of hyperspectral data, particularly in the automated measurement of surface characteristic parameters. With the widespread use of networked ground spectrometers, the performance of these instruments is significantly influenced by environmental conditions, making the accuracy of spectral parameters crucial for reliable radiometric measurements. In this study, we employed a combination of atmospheric absorption features and solar Fraunhofer lines to calibrate and evaluate the spectral parameters of the spectrometer, applying it to an automated measurement spectrometer at the Baotou site, one of the Radiometric Calibration Network (RadCalNet) sites. We evaluated the spectrometer’s spectral parameters and their temporal variations. The field calibration results were validated against laboratory spectral calibration, showing an error of approximately 0.5 nm for CWL offset and 0.3 nm for FWHM variation. Finally, we analyzed the primary factors affecting the accuracy of field spectral calibration, including errors in simulated reference radiance spectra and spectrometer measurements, and assessed the impact of spectral parameter variations on surface reflectance measurements.