Building Facade Information Extraction From Laser Scanning Data

City space information is the core of city information resources. It issynthesized information in continuous space and time distribution that links allother information of city life. It is the foundation work to acquire, operateand update city space information. City space data is usually acquired from aerialphotogrammetry, remote sensing, etc. Vehicle-borne Laser scanner is playing moreand more important role in the process of building "Digital City" with its traitof speediness, real time and high precision. Besides, laser scanner cancomplement the limitation of aerial photogrammetry and remote sensing thatobserves buildings from the top. Data processing and information extraction isthe key problem to make the best use of laser scanner. According to data structureand geometry feature of objects, this paper originally presents three methodsto extract building facade information from scanning data. The "Level—pointsreference" method, used in urban street scanning, filters out valid lines fromscanning data, then picks out valid poiats from valid lines; the "Grid" methodprojects points from 3D space to 2D plane and then detects feature points in smallgrid with density-distribution information; the "Energy" method classifiesenergy value into different ranges, then counts the point number of correspondingobjects to fix threshold value, distinguishing different type of objects fromreflected laser energy. All of the three methods are integrated into a whole,forming a data processing and information extracting system especially for laserscanner.