Estimation of Radiation Environment in Large Area by Satellite Remote Sensing

为了估计大面积的辐射环境，我们在一些软件构建的图像分析系统上对NOAA-AVHRR数据进行分析。在鸟取县的沙丘上进行了地面反照率的原位测量，并与18个月的估计反照率进行了比较。获得了23幅NOAA-AVHRR图像，并进行了几何校正和辐射校正。从这些影像数据中提取地面观测点像元，利用估算模型将其转换为地表反照率。通过与地面测量值的比较，证明沙丘的估计值被低估了。这一结果与作者以往分析中对植被面积高估的估计相反。造成这一相反结果的原因是沙丘区和植被区可见光和红外光谱反射率的差异。通过多元回归分析，综合考虑太阳天顶角、卫星天顶角和太阳与卫星方位角的差异，提高了估算精度。

In order to estimate radiation environment in large area, we analyzed NOAA-AVHRR data on the image analyzing system constructed by some softwares. In situ measurement of surface albedo was carried out on sand dune in Tottori to compare with estimated albedos for eighteen months.Twenty-three scenes of NOAA-AVHRR were obtained and processed through geometric and radiometric correction. The pixel of ground-observation site were extracted from these image data and converted to surface albedo values by using of the estimation model.Estimated values for sand dune were proved to be underestimated by the comparison with ground-measured values. This result was contrary to the estimation for vegetated area overestimated in the past analysis by the authors. The cause of this contrary result is difference of spectral reflectivity in visible and infrared regions for sand dune and vegetated area.By the result of multi-regression analysys, the accuracy of estimation were improved by the consideration of the sun zenith angle, satellite zenith angle and azimuth angle defference of the sun and satellite.