Abstract
This study evaluates the potential of C- and L-band polarimetric SAR data for the discrimination of iron-mineralized laterites in the Brazilian Amazon region. The study area is the N1 plateau located on the northern border of the Carajás Mineral Province, the most important Brazilian mineral province which has numerous mineral deposits, particularly the world’s largest iron deposits. The plateau is covered by low-density savanna-type vegetation (campus rupestres) which contrasts visibly with the dense equatorial forest. The laterites are subdivided into three units: chemical crust, iron-ore duricrust, and hematite, of which only the latter two are of economic interest. Full polarimetric data from the airborne R99B sensor of the SIVAM/CENSIPAM (L-band) system and the RADARSAT-2 satellite (C-band) were evaluated. The study focused on an assessment of distinct schemes for digital classification based on decomposition theory and hybrid approach, which incorporates statistical analysis as input data derived from the target decomposition modeling. The results indicated that the polarimetric classifications presented a poor performance, with global Kappa values below 0.20. The accuracy for the identification of units of economic interest varied from 55% to 89%, albeit with high commission error values. In addition, the results using L-band were considered superior compared to C-band, which suggest that the roughness scale for laterite discrimination in the area is nearer to L than to C-band.
Highlights
The use of radar images in geological surveys is a well-established procedure, and has been employed in several studies in the moist tropics, such as integrated, multisource data procedures [1,2,3,4,5], monoscopic and stereoscopic visual analysis [6], and digital classification based on textural attributes [7]
Techniques based on the target decomposition theory and statistical properties of the backscattered signal constitute the primary approach to the radar polarimetric classifications, which are used mainly in environmental applications, for forest type classifications [8]
Geosciences applications using polarimetric data are still scarce in radar literature, given that this kind of data has only become available with the advent of ALOS (2004) and RADARSAT-2 (2007)
Summary
The use of radar images in geological surveys is a well-established procedure, and has been employed in several studies in the moist tropics, such as integrated, multisource data procedures [1,2,3,4,5], monoscopic and stereoscopic visual analysis [6], and digital classification based on textural attributes [7]. In all these cases, the data were analyzed based on the amplitude or intensity of the backscattered signal. Geosciences applications using polarimetric data are still scarce in radar literature, given that this kind of data has only become available with the advent of ALOS (2004) and RADARSAT-2 (2007)
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