Zhu Changqing

DEM extraction and accuracy assessment based on ZY-3 stereo images

Experiment was carried out using Ziyuan III (ZY-3 for short) stereo images in order to extract DEM and corresponding DEM precision analysis was performed. The DEM was built by using ZY-3 stereo images on ENVI platform, then taking 1:10000 scale DEM as reference data, the extracted DEM and reference DEM were processed in ArcGIS10 platform, such as re-sampling and projection conversion and so on. The extracted DEM elevation accuracy was evaluated effectively by calculating the elevation error and average error indicators. The result shows that the DEM extraction from stereo image of ZY-3 has good feasibility based on ENVI software and the extracted DEM in the hilly and gully region height accuracy can reach 35m with no control points.

A Method of Accuracy Reducing for Vector Data Based on Random Function

Aiming at the safety problems in the vector data sharing process, a method of accuracy reducing for vector data based on random function is proposed. The characteristics of vector data are analyzed, and then the modifying strength is chosen based on the map scale. Finally the data accuracy is reduced by modifying the coordinate values based on the random function. The experiments show that this method maintains the availability of the vector data when reducing the data accuracy. It achieves the goal of protecting the data while maximizing the data sharing.