The calibration of integrated water vapor amount retrieved from Cimel Sun radiometer, the main instrument of the worldwide Sun radiometer network AERONET (http://aeronet.gsfc.nasa.gov) is analyzed. The assessment procedure is based on the using of independent measurements derived from Global Positioning System (GPS) meteorology and parametric solar transmittance methods in solar 940 nm band. The results highlight the importance and the necessity of a continuous and flexible monitoring system for Sun radiometric retrieved water vapor. The established improved calibration procedure is useful in the framework of both water vapor spatial remote sensing calibration and validation activities, and climate applications for which this parameter remains a source of uncertainty.
Spatial remote sensing atmospheric correction algorithms validation remains a challenge particulary over land and coastal environment. To assess this type of algorithm in the case of MERIS scheme, we propose a methodology based on the use of in-situ extinction and sky measurements from the world-wide Sun radiometer network AERONET. The spectral dependency in the blue and red derived from the extinction measurements is used to parameterize an aerosol model defined by the Jung power law size distribution in a first step and a chemical composition represented by a refractive index. This model is used to compute the phase function, a main input to a radiative transfer code (successive order of diffusion based) that allows to simulate the atmospheric parameters (radiances, transmittances). A comparison between the diffuse transmittance from sky measurements and that simulated allow to check the validity of the proposed method. The context of the study is calibration and validation in remote sensing using only the radiative properties of the atmosphere. A sensitivity study of the method to various parameters and an error budget will be reported.
The present work analyzes the potential of NASA EO-1 Hyperion imaging spectrometer to characterize urban structure from summer-based cloud free data over downtown Montreal (Quebec, Canada). This spaceborne hyperspectral sensor provides Earth imagery at 30 m spatial resolution, 7.5 km swath in 220 contiguous spectral bands between 400 and 2500 nm with 10 nm spectral resolution. The investigations were carried out from a slight off-nadir imagery over Montreal (Canada) in order to respond to wireless telecommunication needs. A compiled urban material spectral library is also considered.
Reduction to ground radiance (apparent reflectance) was achieved from several calibration procedures. Thereafter, well-established mapping techniques were considered to characterize urban materials, especially roofs and walls of buildings. The preliminaries results highlight the potential of spaceborne hyperspectral for urban space characterization.