FOV effect analysis in directional brightness temperature observations for urban targets
FOV effect analysis in directional brightness temperature observations for urban targets
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作者：
Ma Wei
利用基于辐射度原理和OpenGL的城市结构简化模型，研究了城市目标的热各向异性状态。通过计算机仿真，研究了不同观测方位、观测高度和传感器与目标之间距离时各组分含量的变化规律。结果表明：（1）DBT（directional brightness temperature）地面平台观测存在显著的视场效应。在垂直于太阳主平面的平面附近，它能够达到最大值。(2)通过对典型城市地表和覆盖形态物理模型在不同空间位置和时间序列上的FOV效应分析，发现在晴天，FOV效应可以达到几摄氏度左右。(3)近地面观测存在明显的“尺度效应”，并且它沿着传感器与城市目标之间的距离而变化。(4)在地面野外实验观测到的DBT与卫星获取的图像之间的比较中，FOV效应不可忽略。
Thermal anisotropy regime for urban targets was investigated using a simplified urban structure model based on the radiosity principles and OpenGL. Each component fraction’s variation regime was examined by computer simulation in different observation zeniths, azimuths and distances between the sensor and targets. Results indicate that: (1) significant field of view (FOV) effect exists in the DBT (directional brightness temperature) ground-based platform observations. It is able to reach the maximum values near the plane perpendicular to the solar main plane. (2) Analysis about FOV effect for a physical model of typical urban surface and cover patterns at different spatial locations and time series reveals that it can achieve several centigrade or so in a sunny day. (3) There is a significant "scale effect" in near-ground observations and it varies along with the distance between the sensor and urban targets. (4) The FOV effect cannot be neglected in comparisons between DBTs observed in ground-based field experiments and in images acquired from satellites.