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Papers by Alan R Gillespie

The ASTER scanner on NASA's Terra (EOS-AM1) satellite will collect five channels of TIR data ... more The ASTER scanner on NASA's Terra (EOS-AM1) satellite will collect five channels of TIR data with an NE ∆T of ≤0.3K to estimate surface kinetic temperatures and emissivity spectra, especially over land, where emissivities are not known in advance. Temperature/emissivity separation (TES) is difficult because there are five measurements but six unknowns. Various approaches have been used to constrain the extra degree of freedom. ASTER's TES algorithm hybridizes two established algorithms, first estimating the temperature and band emissivities by the Normalized Emissivity Method, and then normalizing the emissivities by their average value. Next, an empirical relationship adapted from the Alpha Residual method is used to predict the minimum emissivity from the spectral contrast (min-max difference or MMD) of the normalized values, permitting recovery of the emissivity spectrum with improved accuracy. TES uses an iterative approach to remove reflected sky irradiance. Input to TE...

Abstract: The need to monitor the Earth’s surface over a range of spatial and temporal scales is ... more Abstract: The need to monitor the Earth’s surface over a range of spatial and temporal scales is fundamental in ecosystems planning and management. Change-Vector Analysis (CVA) is a bi-temporal method of change detection that considers the magnitude and direction of change vector. However, many multispectral applications do not make use of the direction component. The procedure most used to calculate the direction component using multiband data is the direction cosine, but the number of output direction cosine images is equal to the number of original bands and has a complex interpretation. This paper proposes a new approach to calculate the spectral direction of change, using the Spectral Angle Mapper and Spectral Correlation Mapper spectral-similarity measures. The chief advantage of this approach is that it generates a single image of change information insensitive to illumination variation. In this paper the magnitude component of the spectral similarity was calculated in two wa...

2009 First Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing, 2009

ABSTRACT

Journal of remote sensing, 1995

The main goals of this thesis were the detailed mapping of Quaternary glacial and other deposits ... more The main goals of this thesis were the detailed mapping of Quaternary glacial and other deposits in these regions, dating of critical events, and geomorphic analysis of the range front. The focus was on Pleistocene moraines near the range front. The motivation of this research was to ...

Spectral Mixture Analysis (SMA) is a standard way of analyzing spectral images in terms of fundam... more Spectral Mixture Analysis (SMA) is a standard way of analyzing spectral images in terms of fundamental components of the scene. For images in reflected sunlight, much of the image variance is caused by lighting variations shadowing and photometric shading that is accounted for by using a shade endmember located close to the origin in a spectral DN space. Under control of the lighting and viewing geometry, shade mixes with the tangible spectral endmembers such as soil and green vegetation to produce the observed spectral radiances. In many scenes, the landscape is vegetated and shade comprises topographic shading and shadowing ("hillshade"), which results from unresolved shadows cast by the canopy ("treeshade") and shadows cast by elements of the canopy ("leafshade"). Hillshade is commonly estimated using digital elevation models (DEMs) and assuming unvegetated surfaces are Lambertian. Deviations from hillshade include treeshade and leafshade. In general...

The ASTER temperature/emissivity separation (TES) algorithm is used to make Standard Products con... more The ASTER temperature/emissivity separation (TES) algorithm is used to make Standard Products containing surface temperature and emissivity images. It operates on land-leaving TIR radiance products, corrected for atmospheric transmissivity and sky radiance. Uncertainties have been attributed to 1) calibration, 2) atmospheric correction, and 3) measurement errors. Uncertainty is also introduced by an empirical power-law regression used to scale ASTER emissivity spectra. The 1-σ accuracy and precision were estimated at 1.5 K and 0.015, respectively, from models before the December 1999 launch of Terra and validated by field experiments. Later, however, errors of 4 K and scaling errors in emissivity were encountered in some images, especially in areas of low spectral contrast. We have undertaken to assess the magnitude and cause of this problem, and to rectify it if possible. It appears that errors in calibration and atmospheric compensation have led to over-correction for reflected do...

Remote Sensing, 2020

Validation of emissivity (ε) retrievals from spaceborne thermal infrared (TIR) sensors typically ... more Validation of emissivity (ε) retrievals from spaceborne thermal infrared (TIR) sensors typically requires spatial extrapolations over several orders of magnitude for a comparison between centimeter-scale laboratory ε measurements and the common decameter and lower resolution of spaceborne TIR data. In the case of NASA’s Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) temperature and ε separation algorithm (TES), this extrapolation becomes especially challenging because TES was originally designed for the geologic surface of Earth, which is typically heterogeneous even at centimeter and decameter scales. Here, we used the airborne TIR hyperspectral Mako sensor with its 2.2 m/pixel resolution, to bridge this scaling issue and robustly link between ASTER TES 90 m/pixel emissivity retrievals and laboratory ε measurements from the Algodones dune field in southern California, USA. The experimental setup included: (i) Laboratory XRD, grain size, and TIR spectral meas...

Remote Sensing, 2020

Permafrost is degrading under current warming conditions, disrupting infrastructure, releasing ca... more Permafrost is degrading under current warming conditions, disrupting infrastructure, releasing carbon from soils, and altering seasonal water availability. Therefore, it is important to quantitatively map the change in the extent and depth of permafrost. We used satellite images of land-surface temperature to recognize and map the zero curtain, i.e., the isothermal period of ground temperature during seasonal freeze and thaw, as a precursor for delineating permafrost boundaries from remotely sensed thermal-infrared data. The phase transition of moisture in the ground allows the zero curtain to occur when near-surface soil moisture thaws or freezes, and also when ice-rich permafrost thaws or freezes. We propose that mapping the zero curtain is a precursor to mapping permafrost at shallow depths. We used ASTER and a MODIS-Aqua daily afternoon land-surface temperature (LST) timeseries to recognize the zero curtain at the 1-km scale as a “proof of concept.” Our regional mapping of the z...

12th Canadian Symposium on Remote Sensing Geoscience and Remote Sensing Symposium,

Simple models for complex natural surfaces-A strategy for the hyperspectral era of remote sensing... more Simple models for complex natural surfaces-A strategy for the hyperspectral era of remote sensing. JOHNB ADAMS, MILTONO SMITH, ALANR GILLESPIE Quantitative remote sensing: An economic tool for the Nineties, 16-21, 1989. ...

Agu Fall Meeting Abstracts, Dec 1, 2004

Common rock-forming minerals have thermal infrared spectral features that are measured in the lab... more Common rock-forming minerals have thermal infrared spectral features that are measured in the laboratory to infer composition. An airborne Daedalus scanner (TIMS) that collects six channels of thermal infrared radiance data (8 to 12 microns), may be used to measure these same features for rock identification. Previously, false-color composite pictures made from channels 1, 3, and 5 and emittance spectra for small areas on these images were used to make lithologic maps. Central wavelength, standard deviation, and amplitude of normal curves regressed on the emittance spectra are related to compositional information for crystalline igneous silicate rocks. As expected, the central wavelength varies systematically with silica content and with modal quartz content. Standard deviation is less sensitive to compositional changes, but large values may result from mixed admixture of vegetation. Compression of the six TIMS channels to three image channels made from the regressed parameters may be effective in improving geologic mapping from TIMS data, and these synthetic images may form a basis for the remote assessment of rock composition.

Photogrammetric Engineering and Remote Sensing, Aug 1, 1977

Proceedings, IEEE Aerospace Conference

ABSTRACT

The ASTER scanner on NASA's Terra (EOS-AM1) satellite will collect five channels of TIR data ... more The ASTER scanner on NASA's Terra (EOS-AM1) satellite will collect five channels of TIR data with an NE ∆T of ≤0.3K to estimate surface kinetic temperatures and emissivity spectra, especially over land, where emissivities are not known in advance. Temperature/emissivity separation (TES) is difficult because there are five measurements but six unknowns. Various approaches have been used to constrain the extra degree of freedom. ASTER's TES algorithm hybridizes two established algorithms, first estimating the temperature and band emissivities by the Normalized Emissivity Method, and then normalizing the emissivities by their average value. Next, an empirical relationship adapted from the Alpha Residual method is used to predict the minimum emissivity from the spectral contrast (min-max difference or MMD) of the normalized values, permitting recovery of the emissivity spectrum with improved accuracy. TES uses an iterative approach to remove reflected sky irradiance. Input to TE...

Abstract: The need to monitor the Earth’s surface over a range of spatial and temporal scales is ... more Abstract: The need to monitor the Earth’s surface over a range of spatial and temporal scales is fundamental in ecosystems planning and management. Change-Vector Analysis (CVA) is a bi-temporal method of change detection that considers the magnitude and direction of change vector. However, many multispectral applications do not make use of the direction component. The procedure most used to calculate the direction component using multiband data is the direction cosine, but the number of output direction cosine images is equal to the number of original bands and has a complex interpretation. This paper proposes a new approach to calculate the spectral direction of change, using the Spectral Angle Mapper and Spectral Correlation Mapper spectral-similarity measures. The chief advantage of this approach is that it generates a single image of change information insensitive to illumination variation. In this paper the magnitude component of the spectral similarity was calculated in two wa...

2009 First Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing, 2009

ABSTRACT

Journal of remote sensing, 1995

The main goals of this thesis were the detailed mapping of Quaternary glacial and other deposits ... more The main goals of this thesis were the detailed mapping of Quaternary glacial and other deposits in these regions, dating of critical events, and geomorphic analysis of the range front. The focus was on Pleistocene moraines near the range front. The motivation of this research was to ...

Spectral Mixture Analysis (SMA) is a standard way of analyzing spectral images in terms of fundam... more Spectral Mixture Analysis (SMA) is a standard way of analyzing spectral images in terms of fundamental components of the scene. For images in reflected sunlight, much of the image variance is caused by lighting variations shadowing and photometric shading that is accounted for by using a shade endmember located close to the origin in a spectral DN space. Under control of the lighting and viewing geometry, shade mixes with the tangible spectral endmembers such as soil and green vegetation to produce the observed spectral radiances. In many scenes, the landscape is vegetated and shade comprises topographic shading and shadowing ("hillshade"), which results from unresolved shadows cast by the canopy ("treeshade") and shadows cast by elements of the canopy ("leafshade"). Hillshade is commonly estimated using digital elevation models (DEMs) and assuming unvegetated surfaces are Lambertian. Deviations from hillshade include treeshade and leafshade. In general...

The ASTER temperature/emissivity separation (TES) algorithm is used to make Standard Products con... more The ASTER temperature/emissivity separation (TES) algorithm is used to make Standard Products containing surface temperature and emissivity images. It operates on land-leaving TIR radiance products, corrected for atmospheric transmissivity and sky radiance. Uncertainties have been attributed to 1) calibration, 2) atmospheric correction, and 3) measurement errors. Uncertainty is also introduced by an empirical power-law regression used to scale ASTER emissivity spectra. The 1-σ accuracy and precision were estimated at 1.5 K and 0.015, respectively, from models before the December 1999 launch of Terra and validated by field experiments. Later, however, errors of 4 K and scaling errors in emissivity were encountered in some images, especially in areas of low spectral contrast. We have undertaken to assess the magnitude and cause of this problem, and to rectify it if possible. It appears that errors in calibration and atmospheric compensation have led to over-correction for reflected do...

Remote Sensing, 2020

Validation of emissivity (ε) retrievals from spaceborne thermal infrared (TIR) sensors typically ... more Validation of emissivity (ε) retrievals from spaceborne thermal infrared (TIR) sensors typically requires spatial extrapolations over several orders of magnitude for a comparison between centimeter-scale laboratory ε measurements and the common decameter and lower resolution of spaceborne TIR data. In the case of NASA’s Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) temperature and ε separation algorithm (TES), this extrapolation becomes especially challenging because TES was originally designed for the geologic surface of Earth, which is typically heterogeneous even at centimeter and decameter scales. Here, we used the airborne TIR hyperspectral Mako sensor with its 2.2 m/pixel resolution, to bridge this scaling issue and robustly link between ASTER TES 90 m/pixel emissivity retrievals and laboratory ε measurements from the Algodones dune field in southern California, USA. The experimental setup included: (i) Laboratory XRD, grain size, and TIR spectral meas...

Remote Sensing, 2020

Permafrost is degrading under current warming conditions, disrupting infrastructure, releasing ca... more Permafrost is degrading under current warming conditions, disrupting infrastructure, releasing carbon from soils, and altering seasonal water availability. Therefore, it is important to quantitatively map the change in the extent and depth of permafrost. We used satellite images of land-surface temperature to recognize and map the zero curtain, i.e., the isothermal period of ground temperature during seasonal freeze and thaw, as a precursor for delineating permafrost boundaries from remotely sensed thermal-infrared data. The phase transition of moisture in the ground allows the zero curtain to occur when near-surface soil moisture thaws or freezes, and also when ice-rich permafrost thaws or freezes. We propose that mapping the zero curtain is a precursor to mapping permafrost at shallow depths. We used ASTER and a MODIS-Aqua daily afternoon land-surface temperature (LST) timeseries to recognize the zero curtain at the 1-km scale as a “proof of concept.” Our regional mapping of the z...

12th Canadian Symposium on Remote Sensing Geoscience and Remote Sensing Symposium,

Simple models for complex natural surfaces-A strategy for the hyperspectral era of remote sensing... more Simple models for complex natural surfaces-A strategy for the hyperspectral era of remote sensing. JOHNB ADAMS, MILTONO SMITH, ALANR GILLESPIE Quantitative remote sensing: An economic tool for the Nineties, 16-21, 1989. ...

Agu Fall Meeting Abstracts, Dec 1, 2004

Common rock-forming minerals have thermal infrared spectral features that are measured in the lab... more Common rock-forming minerals have thermal infrared spectral features that are measured in the laboratory to infer composition. An airborne Daedalus scanner (TIMS) that collects six channels of thermal infrared radiance data (8 to 12 microns), may be used to measure these same features for rock identification. Previously, false-color composite pictures made from channels 1, 3, and 5 and emittance spectra for small areas on these images were used to make lithologic maps. Central wavelength, standard deviation, and amplitude of normal curves regressed on the emittance spectra are related to compositional information for crystalline igneous silicate rocks. As expected, the central wavelength varies systematically with silica content and with modal quartz content. Standard deviation is less sensitive to compositional changes, but large values may result from mixed admixture of vegetation. Compression of the six TIMS channels to three image channels made from the regressed parameters may be effective in improving geologic mapping from TIMS data, and these synthetic images may form a basis for the remote assessment of rock composition.

Photogrammetric Engineering and Remote Sensing, Aug 1, 1977

Proceedings, IEEE Aerospace Conference

ABSTRACT