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Accueil du site → Doctorat → Australie → 1998 → An investigation of mineralogical and textural effects on thermal infrared energy interactions with an arid environment

University of New South Wales (1998)

An investigation of mineralogical and textural effects on thermal infrared energy interactions with an arid environment

Hewson, Robert D.

Titre : An investigation of mineralogical and textural effects on thermal infrared energy interactions with an arid environment

Auteur : Hewson, Robert D.

Université de soutenance : University of New South Wales

Grade : Doctor of Philosophy (Ph. D.) 1998.

This study examines the interactions between thermal infrared radiation and the various components of a land surface in a semi-arid environment. The mineralogical, textural and vegetation features of the experimental farm at Fowlers Gap, western New South Wales, are used to assess these interactions. Detailed laboratory and spectral measurements of field samples, NASA’s Thermal Infrared Multispectral Scanner (TIMS) and CSIRO’s Mid-Infrared Airborne CO 2 Laser Spectrometer (MIRACO2 LAS) data sets were used in the study. The interpretation of these thermal energy interactions has also been assisted by complementary information obtained from AIRSAR radar, airborne radiometics and aeromagnetics. Laboratory CO2 laser spectral measurements of arenaceous rock surfaces and soils compared favourably with FTIR DHR (Fourier transform infrared directional hemispherical reflectance) measurements, suggesting Lambertian-like scattering behaviour. However the highly variable albedo observed in laboratory CO 2 laser spectra of phyllite and shale indicated specular scattering behaviour. Laboratory studies with pure silica samples and wet sieved soil/sediment samples showed that the quartz reststrahlen reflectance feature decreased with an increase in the proportion of the sample finer than 20 μm. This trend is the result of the volume scattering effects of fine quartz and/or clay particles attached to the larger quartz grains. TIMS image data was found to easily discriminate geological units, geomorphological features and vegetation types. These features were partially discriminated on the basis of their quartz and clay mineral contents. Thermal infrared reflectance spectra derived from alpha residual emissivity estimates compared favourably in shape and albedo with FTIR DHR measurements. Linear spectral unmixing of the TIMS emissivity data produced four endmembers : quartz, clay minerals, dry vegetation in fine soils, and green perennial vegetation. MIRACO2 LAS data identified spectral features similar to the quartz, clay mineral, dry vegetation/cellulose and green vegetation/moisture endmembers derived from TIMS data. MIRACO2 LAS data, calibrated to ground reflectance, produced spectra similar in shape to the laboratory CO2 laser spectra of most soils and arenaceous rocks. MIRACO 2 LAS spectral measurements of soils and sediments produced similar trends as the laboratory measurements, relating increased quartz reststrahlen MIRACO 2 LAS reflectances with coarser textures and decreasing clay content. Surface roughness information from AIRSAR’s band C radar backscatter assisted the interpretation of the TIMS data by discriminating scree covered regolith. Airborne radiometrics were also found useful for further discriminating potassium and thorium-bearing phyllosilicate/clay minerals.

Mots clés : Arid regions Research New South Wales Fowlers Gap • Infrared imaging • Remote sensing


Accès au document : Proquest Dissertations & Theses

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