We present a fuzzy logic approach allowing the identification of minerals from re ectance spectra acquired by hyperspectral sensors in the VNIR and SWIR ranges. The fuzzy logic system is based on a human reasoning. It compares the positions of the main and secondary absorptions of the unknown spectrum (spectral characteristics estimated beforehand) with those of a reference database (derived from mineralogical knowledge). The proposed solution is first evaluated on laboratory spectra. It is then applied to airborne HySpex and satellite-borne PRISMA images acquired during a dedicated campaign over two quarries in France. This demonstrates the relevance of the method to automatically identify minerals in different mineralogical contexts and in the presence of mixtures.
The determination of the aerosol type in a plume from remotely sensed data without any a priori knowledge is a challenging task. If several methods have already been developed to characterize the aerosols from multi or hyperspectral data, they are not suited for industrial particles, which have specific physical and optical properties, changing quickly and in a complex way with the distance from the source emission. From radiative transfer equations, we have developed an algorithm, based on a Look-Up Table approach, enabling the determination of the type of this kind of particles from hyperspectral data. It consists in the selection of pixels pairs, located at the transitions between two kinds of grounds (or between an illuminated and a shadow area), then in the comparison between normalized estimated Aerosol Optical Thicknesses (AOTs) and pre-calculated AOTs. The application of this algorithm to simulated data leads to encouraging results: the selection of only six pixels pairs allows the algorithm to differentiate aerosols emitted by a metallurgical plant from biomass burning particles, urban aerosols and particles from an oil depot explosion, regardless the size and the aerosol concentration. The algorithm performances are better for a relatively high AOT but the single scattering approximation does not enable the characterization of thick plumes (AOT above 2.0). However, the choice of transitions (type of grounds) does not seem to significantly affect the results.
This study presents a new theoretical approach for anomaly detection using a priori information about targets. This a
priori knowledge deals with the general spectral behavior and the spatial distribution of targets. In this study, we
consider subpixel and isolated targets which are spectrally anomalous in one region of the spectrum but not in another.
This method is totally different from matched filters which suffer from a relative sensitivity to low errors in the target
spectral signature. We incorporate the spectral a priori knowledge in a new detection distance and we propose a
Bayesian approach with a markovian regularization to suppress the potential targets that do not respect the spatial a
priori. The interest of the method is illustrated on simulated data consisting in realistic anomalies superimposed on a real
HyMap hyperspectral image.
In this paper, variations with wavelength of aerosol optical properties which are optical thickness τ, single-scattering albedo ω0 and asymmetry parameter g are modeled using polynomial functions in the case of dense biomass burning plumes in the spectral range [0.4 - 1.1 μm]. Optical properties are computed from Mie theory for various types of particles, size distributions and concentrations. In a first step, each optical property is fitted by polynomials with one, two and three parameters over the whole set of optical properties and then an error analysis is performed in order to choose the optimal number of parameters depending on wished accuracy. In a second step, the impact of modeling errors on top of atmosphere reflectance ρTOA is investigated depending on ground reflectance. The impact on ρTOA of ground reflectance variability under the smoke plume is also assessed. Calculations show that accurate modeling of spectral behaviour requires three parameters for τ and ω0 and two parameters for g. It leads to simulations of ρTOA with an accuracy of about 0.001 which is compatible with the level of noise of current sensors. Using one less parameter for each optical property yields errors on ρTOA within 0.02.
A method (atmospheric correction via simulated annealing (ACSA)) is proposed that enhances the atmospheric correction of hyperspectral images over dark surfaces. It is based on the minimization of a smoothness criterion to avoid the assumption of linear variations of the reflectance within gas absorption bands. We first show that
this commonly used approach generally fails over dark surfaces when the signal to noise ratio strongly declines. In this case, important residual features highly correlated with the shape of gas absorption bands are observed in the estimated surface reflectance. We add a geometrical constraint to deal with this correlation. A simulated
annealing approach is used to solve this constrained optimization problem. The parameters involved in the implementation of the algorithm (initial temperature, number of iterations, cooling schedule, and correlation threshold) are automatically determined using standard simulated annealing theory, reflectance databases, and
sensor characteristics. Applied to a HyMap image with available ground truths, we verify that ACSA adequately recovers ground reflectance over clear land surfaces and that the added spectral shape constraint does not introduce any spurious feature in the spectrum. The analysis of an AVIRIS image clearly shows the ability of the method to perform enhanced water vapor estimations over dark surfaces. Over a lake (reflectance equal to 0.02, low signal to noise ratio equal to about 6), ACSA retrieves unbiased water vapor amounts (2.86 cm ± 0.36 cm) in agreement with in situ measurements (2.97 cm ± 0.30 cm). This corresponds to a reduction of the standard deviation by a factor 3 in comparison with standard unconstrained procedures (1.95 cm ± 1.08 cm). Similar results are obtained using a Hyperion image containing a very dark area of the land surface.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.