The International Satellite Cloud Climatology Project (ISCCP) D2 dataset is used to study the global dis- tribution of low, middle and high cloud amounts and their trends of 1983—2001. Evidences have shown that globa...The International Satellite Cloud Climatology Project (ISCCP) D2 dataset is used to study the global dis- tribution of low, middle and high cloud amounts and their trends of 1983—2001. Evidences have shown that global warming has accelerated over the past 20 a and the 1990s was the warmest decade in the instrumental records since 1861. Trends of various clouds amounts over this period are analyzed by employing the linear regression method. The results show that global mean total cloud amounts, in general, have tended to reduce over the past 20 a. But there are slightly increasing by about 2% before 1987 and decreasing by about 4% since then. Cloudiness trends of both low and high clouds decrease while increase for the middle cloud. And there exist remarkable discrepancies in different regions. The preliminary analyses suggest that it is likely that the cloud change occurring over the past 20 a is a positive feed- back to global warming.展开更多
数字航空影像和机载点云之间的配准参数精度会直接影响到配准效果,利用共线方程及影像特征点和点云特征点之间计算相似性测度的方法进行参数优化,有效避免了由于初始参数误差导致的配准偏差。首先,提取航空影像及激光雷达(light detecti...数字航空影像和机载点云之间的配准参数精度会直接影响到配准效果,利用共线方程及影像特征点和点云特征点之间计算相似性测度的方法进行参数优化,有效避免了由于初始参数误差导致的配准偏差。首先,提取航空影像及激光雷达(light detection and ranging,LiDAR)点云的特征点;然后,根据初始配准参数及距离误差计算影像与点云之间的匹配点对;最后,通过强制搜索(brute-force,BF)优化方法来寻找更加精确的匹配参数。此外,还构建了2D-3D对应区域的数据集,用于航空影像和机载LiDAR数据配准的相关研究。展开更多
文摘The International Satellite Cloud Climatology Project (ISCCP) D2 dataset is used to study the global dis- tribution of low, middle and high cloud amounts and their trends of 1983—2001. Evidences have shown that global warming has accelerated over the past 20 a and the 1990s was the warmest decade in the instrumental records since 1861. Trends of various clouds amounts over this period are analyzed by employing the linear regression method. The results show that global mean total cloud amounts, in general, have tended to reduce over the past 20 a. But there are slightly increasing by about 2% before 1987 and decreasing by about 4% since then. Cloudiness trends of both low and high clouds decrease while increase for the middle cloud. And there exist remarkable discrepancies in different regions. The preliminary analyses suggest that it is likely that the cloud change occurring over the past 20 a is a positive feed- back to global warming.
文摘数字航空影像和机载点云之间的配准参数精度会直接影响到配准效果,利用共线方程及影像特征点和点云特征点之间计算相似性测度的方法进行参数优化,有效避免了由于初始参数误差导致的配准偏差。首先,提取航空影像及激光雷达(light detection and ranging,LiDAR)点云的特征点;然后,根据初始配准参数及距离误差计算影像与点云之间的匹配点对;最后,通过强制搜索(brute-force,BF)优化方法来寻找更加精确的匹配参数。此外,还构建了2D-3D对应区域的数据集,用于航空影像和机载LiDAR数据配准的相关研究。
