COMPARATIVE ANALYSIS OF GEOREFERENCING 
PROCEDURES USING VARIOUS SOURCES OF CONTROL DATA 
A. Habib 2 , A. Jarvis 2 , A. P. Kersting 2 , Y. Alghamdi 2 
d Department of Geomatics Engineering, University of Calgary, Calgary, Alberta, Canada T2N 1N4 
habib@geomatics.ucalgary.ca - (amyjarvi, ana.kersting, yamalgha)@ucalgary.ca 
Commission IV, WG IV/9 
KEY WORDS: Digital Camera, Georeferencing, Orthoimage Generation, Object Reconstruction, Performance Analysis, Sensor 
Fusion 
ABSTRACT: 
The increasing efficiency and affordability of modem 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. 
1. INTRODUCTION 
Photogrammetric reconstruction procedures aim at deriving 
three-dimensional information from two-dimensional images. 
These procedures create surfaces that are rich in semantic 
information, which can be clearly recognized in the captured 
imagery, and provide highly accurate results due to the inherent 
redundancy associated with photogrammetric reconstruction. 
Many photogrammetric applications, such as mapping and 
orthoimage production, require the interior and exterior 
orientation parameters of the imaging sensor. The interior 
orientation parameters (IOP), which include the principal point 
coordinates, focal length, and distortion parameters, can be 
derived from a camera calibration procedure or obtained from 
the camera manufacturer. The exterior orientation parameters 
(EOP), which include the position and attitude of the camera at 
the time of exposure with respect to object space coordinates 
frame, can be derived either through indirect georeferencing 
using ground control information or direct georeferencing when 
GPS/INS is available onboard the imaging platform. The 
quality of the reconstructed surface is affected by the accuracy 
of the IOP and EOP, and thus it is essential that these 
parameters be determined to a high degree of accuracy. 
In direct georeferencing, the IMU body frame attitude and the 
GPS phase centre position are directly measured using onboard 
GPS/INS systems. In addition, the IMU boresighting angles and 
the GPS antenna offsets relative to the camera perspective 
centre are computed to determine the position (Xo, Yo, Zo) and 
attitude (co, 9, k) of the camera at the time of exposure with 
respect to object space coordinates frame. This approach is 
computationally efficient since only an intersection procedure is 
required, as well as economical in the long run since no ground 
control is required. Nonetheless, indirect georeferencing is 
traditionally favourable due to its accuracy and robustness 
against IOP biases (Cramer et al., 2000). In indirect 
georeferencing, the EOPs are determined indirectly using 
ground control, where the most common type of control 
involves the use of ground control points obtained through field 
surveying procedures. This form of ground control can be 
costly in terms of the required time and effort but has proven to 
be an accurate source of control for the georeferencing 
procedure. 
With the recent developments in spatial acquisition systems, 
however, some reliable alternative forms of control are 
becoming available. In this regard, LiDAR scanning is rapidly 
taking its place in the mapping industry as a fast and cost- 
effective 3-D data acquisition technology for capturing accurate 
positional information from physical surfaces. LiDAR 
georeferencing is directly established through the GPS/INS 
components of the LiDAR system. The increased accuracy and 
affordability of GPS/INS systems are the main reasons behind 
the expanding adoption of LiDAR systems. The use of LiDAR 
derived control has two main advantages. First, it allows for a 
straight-forward integration of LiDAR and photogrammetric 
data, which has numerous benefits such as effective production 
of 3-D city modeling and orthoimage generation. In addition, 
the use of LiDAR control features can eliminate the need for 
ground control points which simplifies the indirect 
georeferencing procedure and makes it more affordable. 
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