Abstract
The process of acquiring and processing in-situ point spectroscopy measurements as ‘ground-truth’ reflectance is often viewed as straightforward and uncomplicated. In reality, the process requires significant attention to detail. This is particularly true as it applies to its use in activities related to the calibration and validation of airborne and/or satellite hyper/multi-spectral imagery where unbiased traceable results are crucial.
In this presentation, I review methodologies employed by the airborne hyperspectral remote sensing group at the National Research Council Canada to optimize the acquisition of in-situ point spectroscopy measurements and the processing of target reflectance spectra as performed in support of a bottomup (lab field airborne satellite (Sentinel-2)) data end-product validation project. In addition, methodologies to assess the quality of the resulting reflectance spectra are discussed.
The laboratory portion of the approach was designed to provide an initial reference panel reflectance characterization in terms of the biconical reflectance factor (BCRF) followed by regular monitoring of panel degradation. Making use of a laboratory implementation of a SVC 1024i field spectrometer, the BCRF of field reflectance reference panels were cross-calibrated at a 0°:45° view/illumination geometry against our primary lab reference panel. This lab panel had, in turn, been calibrated by the Remote Sensing Group at the University of Arizona tying our results to the NIST reflectance standard. Assessment of these data sets, acquired under controlled laboratory conditions, identified potential artifacts related to the detector temperature and integration times in the SVC 1024i field spectrometer. We see many examples where these effects have gone unnoticed within datasets acquired in less aware field deployments.
Experiences related to the acquisition of robust field spectrometry measurements are then reviewed along with methods we apply to evaluate the quality and suitability of the resultant datasets given the less than ideal atmospheric conditions commonly encountered. Biases due to inconsistent location of inscattering objects, reference panel leveling, solar angle procession, and variances in downwelling illumination conditions are also considered.
Experiences Learned in the Acquisition, Processing, and Assessment of In-situ Point Spectroscopy Measurements Supporting Airborne Hyperspectral Cal/Val activities
The process of acquiring and processing in-situ point spectroscopy measurements as ‘ground-truth’ reflectance is often viewed as straightforward and uncomplicated. In reality, the process requires significant attention to detail. This is particularly true as it applies to its use in activities related to the calibration and validation of airborne and/or satellite hyper/multi-spectral imagery where unbiased traceable results are crucial.
In this presentation, I review methodologies employed by the airborne hyperspectral remote sensing group at the National Research Council Canada to optimize the acquisition of in-situ point spectroscopy measurements and the processing of target reflectance spectra as performed in support of a bottomup (lab field airborne satellite (Sentinel-2)) data end-product validation project. In addition, methodologies to assess the quality of the resulting reflectance spectra are discussed.
The laboratory portion of the approach was designed to provide an initial reference panel reflectance characterization in terms of the biconical reflectance factor (BCRF) followed by regular monitoring of panel degradation. Making use of a laboratory implementation of a SVC 1024i field spectrometer, the BCRF of field reflectance reference panels were cross-calibrated at a 0°:45° view/illumination geometry against our primary lab reference panel. This lab panel had, in turn, been calibrated by the Remote Sensing Group at the University of Arizona tying our results to the NIST reflectance standard. Assessment of these data sets, acquired under controlled laboratory conditions, identified potential artifacts related to the detector temperature and integration times in the SVC 1024i field spectrometer. We see many examples where these effects have gone unnoticed within datasets acquired in less aware field deployments.
Experiences related to the acquisition of robust field spectrometry measurements are then reviewed along with methods we apply to evaluate the quality and suitability of the resultant datasets given the less than ideal atmospheric conditions commonly encountered. Biases due to inconsistent location of inscattering objects, reference panel leveling, solar angle procession, and variances in downwelling illumination conditions are also considered.