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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.


Error distribution in view field of thermal camera.
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f5-sensors-08-00800: Error distribution in view field of thermal camera.

Mentions: M, the measured apparent radiance. The uncertainty in M is primarily from the thermal camera itself. Using the blackbody as the sample, we analyzed the characteristics of the thermal camera. Note that, in the measurements, although an auto-adjust function for correcting the temperature drift was set, there still was 4k drift errors at most in one regulating period, moreover, we found that there was almost no error for the central part of the thermal image, while with the increase of the distance from the central, the error increased and can reach 4k, that is to say, there are large errors for the pixels around the edge of the thermal image. According to the magnitude of the errors, the thermal image can be grouped into three regions as shown in Figure.5. The percentage (I) of drift error less than Ik was about 50% and the percentage (II and III) of the other two groups was about 25%, respectively. In order to reduce this error, in terms of the view field of the camera, we installed it at height of 1.3m to make the sample locate in the region of I and II. At the same time, we also calibrated the thermal camera using the blackbody in the experiments.


An Automatic Instrument to Study the Spatial Scaling Behavior of Emissivity
Error distribution in view field of thermal camera.
© Copyright Policy
Related In: Results  -  Collection

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

f5-sensors-08-00800: Error distribution in view field of thermal camera.
Mentions: M, the measured apparent radiance. The uncertainty in M is primarily from the thermal camera itself. Using the blackbody as the sample, we analyzed the characteristics of the thermal camera. Note that, in the measurements, although an auto-adjust function for correcting the temperature drift was set, there still was 4k drift errors at most in one regulating period, moreover, we found that there was almost no error for the central part of the thermal image, while with the increase of the distance from the central, the error increased and can reach 4k, that is to say, there are large errors for the pixels around the edge of the thermal image. According to the magnitude of the errors, the thermal image can be grouped into three regions as shown in Figure.5. The percentage (I) of drift error less than Ik was about 50% and the percentage (II and III) of the other two groups was about 25%, respectively. In order to reduce this error, in terms of the view field of the camera, we installed it at height of 1.3m to make the sample locate in the region of I and II. At the same time, we also calibrated the thermal camera using the blackbody in the experiments.

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.