利用多角度热图像提取冠层组分温度和方向亮温

为了给热辐射方向性研究提供准确的组分温度分布和方向亮温数据,提出了一种新的基于热像仪的实用测量方法.该算法包括2个部分:1)采用"热像仪一定面积法"的改进方法"虚拟圈"结合"交叉点法"自动提取植被冠层方向亮度温度,并进行时间效应纠正;2)在假设发射率已知的条件下,利用"开放度"的概念去除多次散射和天空下行辐射的影响,给出更精确的组分温度分布信息.采用2006年4月20日北京小汤山小麦地的测量数据进行了初步分析.获取的方向亮温可以较好地反映地表热辐射方向性规律,热动力学温度提取误差均值小于1 K.

USING MULTIDIRECTIONAL THERMAL IMAGES TO OBTAIN CANOPY COMPONENT TEMPERATURE AND DIRECTIONAL BRIGHTNESS TEMPERATURE

A new method is designed to obtain canopy component temperature and accurate directional brightness temperature from multidirectional thermal infrared measurements.The algorithm consists of two parts:(1) directional brightness temperature exaction part,which uses a "virtual ring" method based on the "Fixed Area" to obtain the same objects in different images according to the view direction and uses a "cross point" method to correct the time effect;(2) component temperature exaction part,which uses the concept of "soil openness" and "sky openness" to remove the multiple scattering effect and sky downward radiation effect.The measurements of the wheat thermal images(in Beijing,April 20,2006) are used to demonstrate the ability of this method.The results show that the obtained angular variation of surface brightness temperature is rational with average error of less than 1 K.Therefore,this method can be used quantitatively to study the directional thermal emission of the natural surfaces and provide effective data for surface temperature inversion.