ALGORITHM AND APPLICATION DEVELOPMENT FOR PRECISE AND ACCURATE TRANSFORMATION OF LIDAR POINT CLOUDS INTO NATIONAL COORDINATE SYSTEMS OF ROMANIA USING OFFICIAL EQUATIONS AND QUASIGEOID MODEL

Abstract. The LiDAR point clouds are usually processed in Universal Transvers Mercator projection. The transformation to a national coordinate system is frequently made with low accuracy with the help of the generic transformation implemented in the actual softwares. An accurate and precise transformation for LiDAR files in the national coordinate systems of Romania (planimetric system Stereographic 1970 and altimetric system Black Sea 1975) is not yet available. The National Center for Cartography (NCC) from Romania developed a software for precise transformation, but it works only for certain patterns of the text files and for a maximum number of points of about 1 million. Because of this, the use of point clouds in precision work was not possible, using only extracts of low-density grid points in text format. In this research we develop an algorithm which use the precise transformation of NCC to realise an accurate transformation of the LiDAR point clouds in the national coordinate systems. The algorithm is then implemented in an innovative software to transform the LiDAR *LAS files, using the common version 1.2. The software is a batch processing application, which it can process big LiDAR data without blocking. Moreover, the application is capable to apply with accuracy and precision the last published national quasigeoid to the LiDAR point files. In the end, the obtained LiDAR point cloud are more suitable to be used in any domain, because of the accurate and precise transformation in the Romanian coordinate systems.