Abstract
The intrinsic spectral dimensionality indicates the observable degrees of freedom in Earth's solar-reflected light field, quantifying the diversity of spectral content accessible by visible and infrared remote sensing. The solar-reflected regime spans the 0.38 - 2.5 μm interval, and is captured by a wide range of current and planned instruments on both airborne and orbital platforms. To date there has been no systematic study of its spectral dimensionality as a function of space, time, and land cover. Here we report a multi-site, multi-year statistical survey by NASA's "Classic" Airborne Visible Near InfraRed Spectrometer (AVIRIS-C). AVIRIS-C measured large regions of California, USA, spanning wide latitudinal and elevation gradients containing all canonical MODIS land cover types. The spectral uniformity of the AVIRIS-C design enabled consistent in-scene assessment of measurement noise across acquisitions. The estimated dimensionality as a function of cover type ranged from the low 20s to the high 40s, and was approximately 50 for the combined dataset. This result indicates the high diversity of physical processes distinguishable by imaging spectrometers like AVIRIS-C for one region of the Earth.
Highlights
The Visible-ShortWave InfraRed (VSWIR) electromagnetic spectrum from 0.38-2.5 μm contains most surface-reflected solar energy available for remote sensing
The di↵erence may have been related to our spatial coherence criterion, or our estimation of noise independently in each scene rather than a static Noise-Equivalent delta Radiance (NEdL) spectrum
Separating the terrestrial anthropogenic scenes having Cropland, Mosaic, or Urban land cover from other terrestrial scenes, and excluding outliers above dimensionality 50, we found each population was well-characterized by its own Gaussian distribution (Fig. 4, bottom panels)
Summary
The Visible-ShortWave InfraRed (VSWIR) electromagnetic spectrum from 0.38-2.5 μm contains most surface-reflected solar energy available for remote sensing These wavelengths access diverse physical absorption and scattering properties throughout the Earth system. 0.6-2.5 μm wavelengths show vibrational absorption features in solids including iron oxides, phyllosilicates, carbonates, and other materials such as metals and hydrocarbons [4] This reveals a wide range of natural mineralogy and artificial materials in urban environments. Boardman and Green evaluated a historical archive of NASA’s “Classic” Airborne Visible Near Infrared Spectrometer (AVIRIS-C) [10] They found dimensionalities ranging from 20 to 50 for scenes taken independently and far higher for the combined dataset. We sought to (a) evaluate the properties of the dimensionality distribution and its stability over time, (b) test the specific hypothesis of increasing spectral diversity in aquatic, terrestrial natural environments, and urban environments respectively
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