In this paper, the history of the airborne lidar and the development stages of the technology are reviewed. The basic principle of airborne lidar and the method of processing point-cloud data were discussed. At present, single point laser scanning method is widely used in bathymetric survey. Although the method has high ranging accuracy, the data processing and hardware system is too much complicated and expensive. For this reason, this paper present a kind of improved dual-frequency method for bathymetric and sea surface survey, in this method 176 units of 1064nm wavelength laser has been used by push-broom scanning and due to the airborne power limits still use 532nm wavelength single point for bathymetric survey by zigzag scanning. We establish a spatial coordinates for obtaining the WGS-84 of point cloud by using airborne POS system.
Extracting façade texture is the importance part in the produce of constructing virtual city. This paper proposes a novel method to make sure extract the texture image can be maximized. We calculate the azimuth angle and distances between the points belongs to buildings and camera center. And we choose the max and min azimuth angle to determine the boundary of texture image. This paper first employs the DBM (digital building model) and aerial image to search the building’s location in image. After that we also have proposed a method to choose the optimal texture image by calculating the displacement of target building’s corner point. The experimental results demonstrate that the method proposed in this paper can effectively extract texture image and make sure the texture image can be maximized.
Shadows commonly exist in high resolution image, particularly in urban areas .The presence of shadows can represent a serious obstacle for their full exploitation. Especially, because of the complexity of the urban circumstance, there are some factors effecting the shadow detection. For example, the high reflectivity ground, or the glass wall of the building, makes shadow somewhere brighter so that it may cause their intensities close to the non-shadow area. In order to solve these problems, we combine the zero-crossing detection method with the DBM-based geometric method of computing the zenith angle of the sun and the altitude angle of the sun .Firstly, the proposed method uses the zero-crossing detection method to detect the edge of the whole image .Then it selects the edges of both the buildings and their shadows by matching the coordinates of DBM. Because the building and its shadow are adjacent, we match these shadows with the ideal shadow gotten by the DBM-based geometric method to get the only shadow of the building. Compared with other methods, this method may detect the shadow areas of the buildings accurately.
Proc. SPIE. 9808, International Conference on Intelligent Earth Observing and Applications 2015
KEYWORDS: 3D acquisition, Visual process modeling, Data modeling, 3D modeling, Photogrammetry, Computer vision technology, Volume rendering, Machine vision, Airborne remote sensing, 3D image processing
In the realistic 3D model reconstruction, the requirement of the texture is very high. Texture is one of the key factors that affecting realistic of the model and using texture mapping technology to realize. In this paper we present a practical approach of texture mapping based on photogrammetry theory from multiple aerial imageries in urban areas. By collinearity equation to matching the model and imageries, and in order to improving the quality of texture, we describe an automatic approach for select the optimal texture to realized 3D building from the aerial imageries of many strip. The texture of buildings can be automatically matching by the algorithm. The experimental results show that the platform of texture mapping process has a high degree of automation and improve the efficiency of the 3D modeling reconstruction.