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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.


Relationship between Δ ε and standard deviation of surface temperatures.
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f8-sensors-08-00800: Relationship between Δ ε and standard deviation of surface temperatures.

Mentions: According to the design of reference box, there are four sub-pixels, ε1=0.3, ε2=0.98, ε3=0.3, ε4=0.98, a1=a2= a3=a4=0.25, T1=T2, T3=T4. Calculation results show that the magnitude of Δ ε linearly depends on the temperature difference of sub-pixels (T1 – T3). From figure.7, we can see that Δε increases with increase of T1 – T3. When T1 – T3 equals to 38k, Δ ε can reach 0.04, which will produce large errors in surface temperature retrievals. Furthermore, using the emissivity retrievals of combinations of soils and vegetations, we obtained the similar linear results. There are total 240×180 pixels in a thermal image, correspondingly, there are 240×180 surface emissivity values. By integrating pixels of 5×5, 20×20, respectively, we obtained figure.8a and figure.8b, where we used standard deviation of surface temperatures to express the heterogeneity of measured objects. Clearly, the more heterogeneity of the surface is, the larger emissivity difference is. 1.0 deviation of temperature results in about 0.01 emissivity difference. Therefore, Δε must be evaluated and be corrected to fulfill the emissivity scaling.


An Automatic Instrument to Study the Spatial Scaling Behavior of Emissivity
Relationship between Δ ε and standard deviation of surface temperatures.
© Copyright Policy
Related In: Results  -  Collection

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

f8-sensors-08-00800: Relationship between Δ ε and standard deviation of surface temperatures.
Mentions: According to the design of reference box, there are four sub-pixels, ε1=0.3, ε2=0.98, ε3=0.3, ε4=0.98, a1=a2= a3=a4=0.25, T1=T2, T3=T4. Calculation results show that the magnitude of Δ ε linearly depends on the temperature difference of sub-pixels (T1 – T3). From figure.7, we can see that Δε increases with increase of T1 – T3. When T1 – T3 equals to 38k, Δ ε can reach 0.04, which will produce large errors in surface temperature retrievals. Furthermore, using the emissivity retrievals of combinations of soils and vegetations, we obtained the similar linear results. There are total 240×180 pixels in a thermal image, correspondingly, there are 240×180 surface emissivity values. By integrating pixels of 5×5, 20×20, respectively, we obtained figure.8a and figure.8b, where we used standard deviation of surface temperatures to express the heterogeneity of measured objects. Clearly, the more heterogeneity of the surface is, the larger emissivity difference is. 1.0 deviation of temperature results in about 0.01 emissivity difference. Therefore, Δε must be evaluated and be corrected to fulfill the emissivity scaling.

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.