Quantifying Libya-4 Surface Reflectance Heterogeneity With WorldView-1, 2 and EO-1 Hyperion

Neigh, C. S. R.; McCorkel, Joel; Middleton, Elizabeth M.

doi:10.1109/lgrs.2015.2468174

Cited by 12 publications

(15 citation statements)

References 25 publications

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“…They are all located in the Sahara: Algeria3, Algeria5, Libya1, Libya4, Mauritania1 and Mauritania2. They have been extensively used for developing/improving the calibration method [4][5][6][7], and for operational calibration/radiometric inter-comparison of space-borne sensors [8][9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Revisiting Pseudo Invariant Calibration Sites (PICS) Over Sand Deserts for Vicarious Calibration of Optical Imagers at 20 km and 100 km Scales

et al. 2019

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In-flight assessment of the radiometric performances of space-borne instruments can be achieved by means of vicarious calibration over Pseudo-Invariant Calibration Sites (PICS). PICS are chosen for the high temporal stability of their surface optical properties combined with a high spatial homogeneity. A first list of the main desert PIC sites was identified 20 years ago for the calibration of medium/coarse spatial resolution instruments in the solar spectral range (400–2500 nm). They are located in the Saharan desert and in the Arabian Peninsula. Six of them have since been endorsed by the CEOS/WGCV/IVOS as reference Calibration/Validation test sites. In this study, we have revisited the list of desert PIC sites at the global scale with the aim of (1) assessing if these twenty PICS are still “optimal”, in terms of temporal stability and spatial uniformity, and using up-to-date multi-spectral remote sensing data, and (2) identifying new calibration sites distributed over other areas of the world. We verified that the original sites remain very relevant, although alternate locations in their close vicinity have slightly better characteristics. We proposed four additional targets with similar characteristics, some of which may offer easier logistical access. In order to support radiative transfer simulations of satellite sensor measurements over the sites, we assessed the abilities of several semi-empirical models to reproduce the spectro-directional signatures of six IVOS sites and the four new candidate sites, and we derived climatologies of the main atmospheric properties (trace gas column load and aerosol optical depth).

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Section: Introductionmentioning

confidence: 99%

Revisiting Pseudo Invariant Calibration Sites (PICS) Over Sand Deserts for Vicarious Calibration of Optical Imagers at 20 km and 100 km Scales

et al. 2019

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“…Mishra et al [18] used Hyperion data to extend a cross-calibration model through visible and near-infrared (VNIR) wavelengths for the Landsat 7 Enhanced Thematic Mapper + found accuracies of 3% with an uncertainty of ~2%. As noted in our prior study, Neigh et al [21] found that dune peaks have higher surface reflectance originating from sand properties related to grain size, shape and composition [22,23], whereas dune ridges have more variability in BRDF due to shadowing [24]. These studies incorporated Hyperion's narrow band VNIR and shortwave infrared (SWIR) spectrum to improve cross calibration estimates among other satellite sensors.…”

Section: Index Terms-pseudo-invariant Calibration Site (Pics) Land Surface Imaging (Lsi) Eo-1 Hyperion Surface Reflectance Libya-4 Time-smentioning

confidence: 83%

“…INTRODUCTION Analysis of EO-1 Hyperion high spectral resolution imagery (0.4 -2.5 μm) is needed to link data products for cross-calibration [1]. These data could be used for multi-spectral data replication, or for on orbit cross-calibration among satellite instruments [1][2][3][4] to create a land surface imaging (LSI) virtual constellation approach of merging similar but disparate satellite records. Estimating trends in Hyperion products due to precision could support future LSI studies, as the LSI virtual constellation concept is only viable if the stability of constituents is known with uncertainties.…”

Section: Index Terms-pseudo-invariant Calibration Site (Pics) Land Surface Imaging (Lsi) Eo-1 Hyperion Surface Reflectance Libya-4 Time-smentioning

confidence: 99%

“…Libya-4 is part of the Sahara desert, commonly referred to as the "seas of sand" (see Fig. 1 from Neigh et al [21]), and has a mean terrain height of 113 m above sea level. Typically, atmospheric aerosols and cloud cover are low, making it an ideal location for cross comparing Earth-observing sensors.…”

Section: Index Terms-pseudo-invariant Calibration Site (Pics) Land Surface Imaging (Lsi) Eo-1 Hyperion Surface Reflectance Libya-4 Time-smentioning

confidence: 99%

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Monitoring Orbital Precession of EO-1 Hyperion With Three Atmospheric Correction Models in the Libya-4 PICS

Neigh

McCorkel

Campbell

et al. 2016

IEEE Geosci. Remote Sensing Lett.

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-Spaceborne spectrometers require spectral-temporal stability characterization 12 to aid validation of derived data products. EO-1 began orbital precession in 2011 after exhausting onboard fuel resources. In the Libya-4 Pseudo Invariant Calibration Site (PICS) this resulted in a progressive shift from a mean local equatorial crossing time of ~10:00 AM in 2011 to ~8:30 AM in late 2015. Here, we studied precession impacts to Hyperion surface reflectance products using three atmospheric correction approaches from 2004 to 2015. Combined difference estimates of surface reflectance were < 5% in the visible near infrared (VNIR) and < 10% for most of the shortwave infrared (SWIR). Combined coefficient of variation (CV) estimates in the VNIR ranged from 0.025 -0.095, and in the SWIR ranged from 0.025 -0.06, excluding bands near atmospheric absorption features. Reflectances produced with different atmospheric models were correlated (R 2 ) in 22 VNIR from 0.25 -0.94 and SWIR from 0.12 -0.88 (p < 0.01). The uncertainties in all 23 models increased with terrain slope up to 15° and selecting dune flats could reduce errors. 24We conclude that these data remain a useful resource over this period. 25

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“…Vicarious calibration practices, making use of some combination of: 'invariant' natural targets on the Earth or in space (such as the moon); absolutely traceable satellite 'reference calibration' measurements; and high-quality in-situ based observational capabilities, have to be put in place (e.g. Neigh, McCorkel, and Middleton 2015).…”

Section: The Theoretical Basis Underlying Cal/valmentioning

confidence: 99%

Towards a European Cal/Val service for earth observation

Sterckx

Brown

Kääb

et al. 2020

International Journal of Remote Sensing

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Societal dependence on, and commercial and scientific exploitation of Earth-Oriented remote sensing from satellites is growing at an exponential rate. The comprehensive EU Copernicus programme provides a major contribution to the global effort, but even so, to achieve the necessary global and temporal coverage requires synergistic cooperation and associated interoperability of the Worlds sensors. For a user to exploit Earth Observation (EO) data there must exist confidence in data characteristics, quality and reliable delivery. Although long-term data records for climate may be the most demanding in nature, generation of analysis-ready operational data sets for applications, as diverse as food security to pollution monitoring, all require the user to have some quantitative level of confidence in the data and derived information. A longterm Calibration/Validation (Cal/Val) vision necessitates clear ownership and long-term funding. Delineating the roles of the European Commission (EC), space agencies and member states in long-term Cal/Val would provide clarity. It is clear that the space agencies have the responsibility to meet the mission requirement of their spaceborne instruments but long-term validation is often entrusted to interested parties bringing their own resources to the task. Furthermore, there is a critical need for Fiducial Reference Measurements (FRMs), acquired in operational mode, and comprehensive in coverage both spatially and temporally, to assure that the satellite product accuracies are met. This paper discusses the current status, gaps and challenges regarding long-term Cal/Val of EO satellites and recommends the creation of a European coordinating entity for satellite product calibration and validation. The proposed entity would be an integrative organization coordinating the European Cal/Val activities in partnership with the member states and the space agencies and working together with existing data providers to secure access to satellite and in-situ data of traceable FRM standards.

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Quantifying Libya-4 Surface Reflectance Heterogeneity With WorldView-1, 2 and EO-1 Hyperion

Cited by 12 publications

References 25 publications

Revisiting Pseudo Invariant Calibration Sites (PICS) Over Sand Deserts for Vicarious Calibration of Optical Imagers at 20 km and 100 km Scales

Revisiting Pseudo Invariant Calibration Sites (PICS) Over Sand Deserts for Vicarious Calibration of Optical Imagers at 20 km and 100 km Scales

Monitoring Orbital Precession of EO-1 Hyperion With Three Atmospheric Correction Models in the Libya-4 PICS

Towards a European Cal/Val service for earth observation

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