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An Automatic Instrument to Study the Spatial Scaling Behavior of Emissivity

View Article: PubMed Central - PubMed

ABSTRACT

In this paper, the design of an automatic instrument for measuring the spatial distribution of land surface emissivity is presented, which makes the direct in situ measurement of the spatial distribution of emissivity possible. The significance of this new instrument lies in two aspects. One is that it helps to investigate the spatial scaling behavior of emissivity and temperature; the other is that, the design of the instrument provides theoretical and practical foundations for the implement of measuring distribution of surface emissivity on airborne or spaceborne. To improve the accuracy of the measurements, the emissivity measurement and its uncertainty are examined in a series of carefully designed experiments. The impact of the variation of target temperature and the environmental irradiance on the measurement of emissivity is analyzed as well. In addition, the ideal temperature difference between hot environment and cool environment is obtained based on numerical simulations. Finally, the scaling behavior of surface emissivity caused by the heterogeneity of target is discussed.

No MeSH data available.


Picture of reference boxes: a) upper surface; b) undersurface.
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f2-sensors-08-00800: Picture of reference boxes: a) upper surface; b) undersurface.

Mentions: For calculating the ambient radiance, the reference boxes with known emissivities were used, which is shown in Figure.2. It consisted of two hollow boxes made of aluminium. One half upper surface of every box was sprayed with a layer of black lacquer with high emissivity about 0.98. The other half and its undersurface were polished to grey-white body with an average surface roughness of 2-5 urn which can give low emissivity about 0.3 without specular reflection. The first value of emissivity is given by the manufacturer of the black paint; the second one has been determined by means of a portable instrument for measuring emissivity which has been validated in previous applications (Patent no, ZL 02 1 23745.X). There is a hole on the upper surface of every box, through which water with some temperature can be poured into it to make the box an isothermal surface and to control the surface temperature of the box. The size of reference boxes is 0.4m length and 0.3m width, which is determined according to the installation height and view field of the thermal camera.


An Automatic Instrument to Study the Spatial Scaling Behavior of Emissivity
Picture of reference boxes: a) upper surface; b) undersurface.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3927495&req=5

f2-sensors-08-00800: Picture of reference boxes: a) upper surface; b) undersurface.
Mentions: For calculating the ambient radiance, the reference boxes with known emissivities were used, which is shown in Figure.2. It consisted of two hollow boxes made of aluminium. One half upper surface of every box was sprayed with a layer of black lacquer with high emissivity about 0.98. The other half and its undersurface were polished to grey-white body with an average surface roughness of 2-5 urn which can give low emissivity about 0.3 without specular reflection. The first value of emissivity is given by the manufacturer of the black paint; the second one has been determined by means of a portable instrument for measuring emissivity which has been validated in previous applications (Patent no, ZL 02 1 23745.X). There is a hole on the upper surface of every box, through which water with some temperature can be poured into it to make the box an isothermal surface and to control the surface temperature of the box. The size of reference boxes is 0.4m length and 0.3m width, which is determined according to the installation height and view field of the thermal camera.

View Article: PubMed Central - PubMed

ABSTRACT

In this paper, the design of an automatic instrument for measuring the spatial distribution of land surface emissivity is presented, which makes the direct in situ measurement of the spatial distribution of emissivity possible. The significance of this new instrument lies in two aspects. One is that it helps to investigate the spatial scaling behavior of emissivity and temperature; the other is that, the design of the instrument provides theoretical and practical foundations for the implement of measuring distribution of surface emissivity on airborne or spaceborne. To improve the accuracy of the measurements, the emissivity measurement and its uncertainty are examined in a series of carefully designed experiments. The impact of the variation of target temperature and the environmental irradiance on the measurement of emissivity is analyzed as well. In addition, the ideal temperature difference between hot environment and cool environment is obtained based on numerical simulations. Finally, the scaling behavior of surface emissivity caused by the heterogeneity of target is discussed.

No MeSH data available.