Comparative Analysis of Georeferencing Procedures Using Various Sources of Control Data

The increasing efficiency and affordability of modern spatial acquisition systems, such as LiDAR, have provided reliable alternative sources of control data for image georeferencing. Indirect georeferencing using LiDAR control features to derive the exterior orientation parameters (EOP) allows for a straight-forward integration of LiDAR and photogrammetric data which can be used, for example, for more effective orthoimage generation and 3-D city modeling. This paper presents a comparative analysis of indirect georeferencing by investigating the use of three sources of control data, namely, ground control points, LiDAR patches, and LiDAR lines. In this regard, ground control points are obtained through GPS surveying and are used to derive the EOPs of the involved imagery. Point features cannot be distinguished in LiDAR data however, and thus when using LiDAR as the source of control for photogrammetric georeferencing, linear and areal features are used. Moreover, a semi-automated approach for the extraction of lines and patches from LiDAR data is presented. Linear and areal features are identified in the imagery while conjugate LiDAR features are extracted through planar patch segmentation and intersection. Following the extraction procedure, the mathematical models for incorporating the image and LiDAR features for georeferencing are discussed. RMSE analysis and orthoimage generation using the three sets of EOP – obtained from GCPs, LiDAR patches, and LiDAR lines – are used to quantitatively and qualitatively compare the object reconstruction results using the three sources of control data. Finally, the practicality issues of these methods are compared in terms of the effort involved in the derivation of control information and the underlying procedures.