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The measurement, description and analysis of reflected polarized visible light for remote sensing purposes : a ground-based study

The measurement, description and analysis of reflected polarized visible light for remote sensing purposes : a ground-based study
The measurement, description and analysis of reflected polarized visible light for remote sensing purposes : a ground-based study

Upon reflection or surface scattering, unpolarized light will receive a degree of polarization which may be measured independently of its spectral properties. This polarization contains new and potentially useful information about the surface which may enhance purely spectral information. This research shows how a broad band field radiometer may be converted into a polarimeter. It has also developed a technique which allows the collection of useful polarimetric data under field conditions.

The instrument constructed for this study recorded polarized light from the entire visible spectrum and it is shown that measurements of polarized radiance made without the use of a calibrating or reference panel may be used to describe surfaces such as grass and asphalt. This is an important simplification for field surveys where changing environmental and irradiance factors limit data collection to periods 1 hour either side of solar noon.

The field technique developed by this research is based upon the methods employed by astronomers when investigating planetary surfaces. It is shown that a planetary type model of polarization can be applied to both vegetation canopies and unvegetated surfaces, when data are plotted on polarization curves. The construction of these curves requires that data be collected over a range of phase angles. In many remote sensing investigations this is not possible, therefore a polarization feature space has been developed to allow the presentation of all the important polarization parameters from natural scenes on a single diagram.

Polarimetric data presented in this study cannot be considered to be absolute measures of polarization because it is shown that data are influenced by a bias induced into the values by the polarimeter itself. Furthermore, values also vary both in the long and short term. On a daily basis polarimetric values of an asphalt surface are shown to correlate with the maximum temperature and relative humidity, while over a period of a few years the polarimetric response of heath canopies is shown to change. It is suspected that water stress within the canopy may be one cause of this change.

Traverse and plot surveys of heath canopies are only partially successful at discriminating between canopy types. The problems of sampling from within these spatially variable canopies has not been fully resolved, but the data indicate that studies of polarimetric texture may be most fruitful when considering such surfaces.

University of Southampton
Macdonald, John Cameron
Macdonald, John Cameron

Macdonald, John Cameron (1991) The measurement, description and analysis of reflected polarized visible light for remote sensing purposes : a ground-based study. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

Upon reflection or surface scattering, unpolarized light will receive a degree of polarization which may be measured independently of its spectral properties. This polarization contains new and potentially useful information about the surface which may enhance purely spectral information. This research shows how a broad band field radiometer may be converted into a polarimeter. It has also developed a technique which allows the collection of useful polarimetric data under field conditions.

The instrument constructed for this study recorded polarized light from the entire visible spectrum and it is shown that measurements of polarized radiance made without the use of a calibrating or reference panel may be used to describe surfaces such as grass and asphalt. This is an important simplification for field surveys where changing environmental and irradiance factors limit data collection to periods 1 hour either side of solar noon.

The field technique developed by this research is based upon the methods employed by astronomers when investigating planetary surfaces. It is shown that a planetary type model of polarization can be applied to both vegetation canopies and unvegetated surfaces, when data are plotted on polarization curves. The construction of these curves requires that data be collected over a range of phase angles. In many remote sensing investigations this is not possible, therefore a polarization feature space has been developed to allow the presentation of all the important polarization parameters from natural scenes on a single diagram.

Polarimetric data presented in this study cannot be considered to be absolute measures of polarization because it is shown that data are influenced by a bias induced into the values by the polarimeter itself. Furthermore, values also vary both in the long and short term. On a daily basis polarimetric values of an asphalt surface are shown to correlate with the maximum temperature and relative humidity, while over a period of a few years the polarimetric response of heath canopies is shown to change. It is suspected that water stress within the canopy may be one cause of this change.

Traverse and plot surveys of heath canopies are only partially successful at discriminating between canopy types. The problems of sampling from within these spatially variable canopies has not been fully resolved, but the data indicate that studies of polarimetric texture may be most fruitful when considering such surfaces.

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More information

Published date: 1991

Identifiers

Local EPrints ID: 460913
URI: http://eprints.soton.ac.uk/id/eprint/460913
PURE UUID: fb3fc682-3877-4886-a842-b1c1bba392ec

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Date deposited: 04 Jul 2022 18:32
Last modified: 04 Jul 2022 18:32

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Contributors

Author: John Cameron Macdonald

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