Mapping saline soils using Hyperion hyperspectral images data in Mleta plain of the Watershed of the great Oran Sebkha (West Algeria)
Abstract
The hyperspectral optical imagery constitutes a significant mine of information. These images reveal valuable information about soil conditions and can be used successfully in the saline soils mapping domain. Currently, the use of spatial hyperspectral image is considered to be a most spectacular technological revolution, because it has the advantage to reconstruct almost the entire spectrum of each images pixel. This characteristic, which is connected to the large number of bands, is achieved at the expense of the size of the image swath on the ground. Only one scene satellite Hyperion image composed of more than two hundred twenty (220) images was used to cover the central part of the Mleta plain. These images are corrected on radiometric and atmospheric plan. The atmospheric corrections are made by FLAASH module using the MODTRAN radiative transfer model. This operation will subtract the values of absorbed radiation and layers atmospheric backscattered to find in the end the true reflectance values at ground level. The classification, based on almost continuous spectral information of the thematic objects across the electromagnetic spectrum, applied on these images will allow highlighting the different saline soils classes.
Two mapping methods have been used to mapping salinity. The first method is made from a colored composition between the first MNF (Minimum Noise Fraction) images. As for the second, it is done using a SAM (Spectral Angle Mapper) classification method based on information contained in the various spectral calculated from the image and compared with those of the spectral library.
Keywords
Download Options
Introduction
The evolution of airborne hyperspectral sensors has enriched the spaceport and space remote sensing images of more and more precise and detailed. The Hyperspectral remote sensing provides medium resolution images with fine spectral range in the visible and infrared. With a wide spectral range, the hyperspectral data has seen expansions in earth observation in civil and defense applications.
The Hyperion sensor images are obtained through an spectro-imager. The acquisition of a same scene is completed in the two hundred forty two (242) spectral bands. These bands form a quasi-continuous reflectance spectrum for each object on image. The first seventy (70) bands cover the spectrum of the visible and near infrared (356nm-1058 nm) and one hundred seventy two (172) bands in the short wavelength infrared (852nm-2577nm). From the set of bands (242), only one hundred ninety eight (198) bands are calibrated. It’s due to overlap between bands of the visible and infrared, it remains only 196 unique channels. The calibrated channels are (8-57) for the visible and near-infrared and (77-224) for the average infrared channels.
Conclusion
The use of the Hyperion hyperspectral imagery is growing and a wide field of application. They have the advantage to reproducing continuous spectral responses of the imaged objects.
In the field of photo-interpretation, the results indicate that hyperspectral satellite imagery is a source of reliable data for mapping the saline soil.
The different treatments applied to these images reveal interesting results in the localization and distribution of soil salt in the Mleta plain.
The results are very interesting, because knowledge of the spectral response of the salts present in the study area increases the quality and reliability of the used salinity mapping method.