Abstract
In this work the MIVIS (Multispectral Infrared and Visible Imaging Spectrometer) hyperspectral data, acquired during aerial campaigns made in 1998 over the Pollino National Park in the framework of the «Progetto Pollino», have been used to set up a supervised technique devoted to identify the presence of selected rocky outcrops. Tests have been performed over an extended area characterised by a complex orography. Within this area, serpentinite was chosen as a test-rock because it is present in isolated outcrops, distributed all over the test-area, besides subtending important problems of environmental nature as it contains asbestos. Geological information, coming from field observations or geological maps, was used to trigger the algorithms and as ground truth for its validation. Two spectral analysis techniques, SAM (Spectral Angle Mapper) and LSU (Linear Spectral Unmixing), have been applied and their results n combined to automatically identify serpentinite outcrops and, in some cases, to mark its boundaries. The approach used in this work is characterised by simplicity (no atmosphere and illumination corrections were performed on MIVIS data), robustness (material of interest is identified for certainty) and intrinsic exportability (the method proposed can be applied on different geographic areas and, in theory, to identify any kind of material because no datum about atmospheric and illumination conditions is required).
Highlights
It is well-known that any material reflects or emits radiation with different intensity at different wavelength, according to its own physicalchemical properties.Theoretically, it is possible to identify different materials by analysing their characteristic spectral response on the basis of suitable multi-spectral radiometric measures.That has been done in controlled laboratory conditions and attested by a number of published works reporting laboratory spectral signatures of almost any material (e.g., Clark et al, 1990; Salisbury and D’Aria, 1992).A number of additional problems arise when surface material identification is attempted by airborne multispectral sensors
Vegetated areas were excluded from the following processing steps by generating a vegetation mask on the basis of spectral signatures, specific to the vegetated surfaces, in the available VIS and TIR MIVIS channels: the MIVIS bands ratio, channel 6/channel 13 (i.e. 0.542 μm/0.682 μm), is known to be generally higher whereas the radiant temperature in channel 93 (8.37 μm) is expected systematically lower for vegetated pixels compared with non-vegetated areas
In order to verify SAM results, MIVIS imagery and image processing products were preliminarily co-registered upon available digital geological maps of the investigated area
Summary
It is well-known that any material reflects or emits radiation with different intensity at different wavelength, according to its own physicalchemical properties. Not present during laboratory observations, which could affect remotely sensed spectra are mainly related to the illumination conditions (in the solar spectral range) the angles of view and surface homogeneity within the ground resolution cell. 2a, the differences between MIVIS reflectance spectra and the laboratory ones (due mainly to the presence of the atmosphere, different observational conditions and possible soil heterogeneity within the ground resolution cell) are quite evident. Many airborne hyperspectral sensors (AVIRIS, HYDICE, DAIS, HYMAP, etc.) are active They are able to acquire data in a great number of narrow spectral bands which, in theory, obtain from airborne or spaceborne platforms, spectral response curves comparable with those obtained in the laboratory.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
