Quality Check Methods For 1:2000 Digital Line Graphic

Digital Line Graphic (DLG) is one of the most fundamental and important carrier of information. Data quality has greater impact on applications in various fields. In order to obtain higher accuracy of data, it is very important to research the methods of quality check which was taken by computer technology and geographic information systems technology.This thesis primarily researches quality problem of 1:2000DLG which based on LIDAR data. DLG has the characteristic of large volume of data and complexity of data quality check technical and so on. It will lead to low efficiency of inspection, more mistakes and non-standard in check results if we still use the traditional inspection methods and modes in the production and inspection and warehousing. Therefore, it is essential to develop a quality check software with targeted, comprehensive, efficiency. The main contents are as follows:1. The background and purpose are introduced.2. The concept and characteristics of DLG data,1:2000DLG data production methods are summarized. The basic features of spatial data quality are introduced and the factors affecting data quality are analyzed. The contents and principles of inspection according to national spatial data quality check standards are given. Finally, the data quality check methods are discussed.3. The property, quality problem and quality check methods of contour line are researched, such as contradiction of elevation point with contour line, contour intersection, contour discount and contour self-intersection. Quality check methods of contradiction of elevation point with contour line are primarily researched. Contradiction of elevation point with contour line uses constitutive TIN. Flat triangle repair algorithms are modified. Flat triangles are repaired according to non-flat triangle numbers. It is effective to improve the accuracy of contradiction of elevation point with contour line after flat triangle repaired.4. The principles and methods of system are expatiated on. The whole and detailed designs of system are given and the prototypes of system are exploited. The experiments are implemented using 1:2000DLG and the check methods are proved effectively about the wrong of elevation point with contour line, contour intersection, contour discount and contour self—intersection etc.Visual Studio.net 2005 (C#), ArcGIS Engine 9.2 and Access 2003 are used as developed tool and most modules of this system have been designed. The quality check methods of DLG can be extended to related projects, which play a certain role in carrying out quality check of mapping products.