Estimation of Radiation Environment in Large Area by Satellite Remote Sensing

为了对大面积的辐射环境进行评价，我们利用NOAA-AVHRR数据，通过相关软件构建图像分析系统，对数据进行了分析。在鸟取县沙丘上进行了18个月的地面反射率的现场测量，并与估算的反射率进行了比较，获得了23幅NOAA-AVHRR图像，并对图像进行了几何和辐射校正。从这些影像数据中提取出地面观测点的像元，并利用估算模型将其转换为地表覆盖值，通过与地面实测值的比较，证明了沙丘的估算值被低估。这一结果与作者过去分析中高估植被面积的估计相反。结果表明，沙丘和植被覆盖区在可见光区和红外区的光谱反射率差异是造成这一相反结果的原因，通过多元回归分析，考虑了太阳天顶角、卫星天顶角和太阳与卫星方位角的差异，提高了估算的精度。

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.