| An airborne LiDAR system can quickly and accurately obtain point cloud coordinates on the surface of the earth,currently,it has become the main technical means to collect surveying and mapping and geographic information.Because of LiDAR's components themselves and their integration,systematic errors occur between overlapped strips,coordinates of same object's point cloud collected by different strips are different.Strip adjustment uses corresponding blocks or the same name available features in overlapped strips to convert each strip point cloud to a unified coordinate system,this way can weaken systematic errors.Existing strip adjustment method mainly use single geometric feature.Point cloud data contains a large number of available point,line features,therefore,this paper extracts point,line features for strip adjustment.The main contents are listed as following:?To extract point features in point cloud.Center of gravity belongs to the fitting characteristics.Calculating the mean value of all the coordinates of point cloud on the same plane as the center of gravity.?To extract line features in point cloud.Line feature extraction is respectively using the least squares fitting both sides of the plane, then using fitting planes to produce intersection line features.?To accomplish airborne LiDAR strip adjustment based on point,line features.Conjugate features identified in different air strips will maintain the invariant properties when they are transformed into other coordinate systems,which makes it possible that the observation equations can use point,line features to solve the parameters of coordinate transformation by the adjustment.The experimental results show that feature-based adjustment only uses point,line features can effectively reduce the systematic error,line feature is not affected by shade.When the distribution is appropriate,strip adjustment combined point,line features can be more effective than using single feature. |
PDF Full Text Request