基于Otsu的建筑物点云分割改进算法

提出了一种基于Otsu的建筑物点云分割改进算法,针对传统Otsu分割算法在精确性方面的不足提出2点修改意见。首先根据投影点密度理论将三维点云转换为二维灰度图像,再利用Otsu算法及其改进算法对图像进行分割。采用Riegl公司VZ-400激光扫描仪采集的武汉大学信息学部第一教学楼的点云进行分割处理,并与传统的Otsu分割算法进行对比。结果表明,该算法分割正确率可达96.54%,远高于改进前的72.82%。

First extensive and cost-effective quality check of Crisis Maps: presentation of assessment parameters and results

The digital representation of disaster situations into maps,mainly based on remotely sensed observations,is becoming a widely used instrument for emergency management.Thousands of maps are being produced all over the world and big attention is paid by international institutions,such as the World Bank,the United Nations and the European Commission to these tools.The quality of crisis maps is a crucial element to ensure effectiveness in the disaster response chain,but it is often neglected with respect to the need for a rapid delivery.In this paper a sample of crisis maps produced between 2005 and 2010 by world leader providers has been evaluated through around 40 parameters assessed by visual analysis and extracted from the validation protocol designed at the Joint Research Centre(JRC)of the European Commission.The maps turned out to be in most cases clearly readable,but some gaps and inconsistencies have been singled out,due to the lack of international standard references.The results are analysed in detail and some remarks are presented.