1071 
INFLUENCE FACTORS EVALUATION ON HIGH-PRECISION PLANAR 
CALIBRATION OF NON-METRIC DIGITAL CAMERA 
Wenjin Wang 3 , Bingxuan Guo a , Xin Li b , Jing Cao 3 
d State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, 
Wuhan University, China. Wenjin_rs@126.com 
b School of Remote Sensing and Information Engineering,Wuhan University, 129 Luoyu Road,Wuhan,China,430079) 
Commission I, ThS-2 
KEY WORDS: Camera calibration, influence factors, planar calibration 
ABSTRACT: 
With the rapid development of three-dimensional (3D) modelling, camera calibration is paid more and more attention. In this article, 
we analyse the influence factors in the calibration: the camera and lens, the shape of control points, photography model and the scale 
between calibration object and measurement. Appropriate model can get the right result quickly, and the position of the model in the 
image effects the calibration result directly. The control points should cover the whole image evenly. The cross control point is 
better than circle points. The more similar the size of object model and the measurement object, the higher precision the calibration 
has. Actually, each of them plays an important part in calibration. We can get higher precision result based on considering those 
influence factors. And the experiments in the end show that the work is worthy. It means that we should take those factors into 
account. 
1. INTRODUCTION 
1.1 Background 
With the rapid development of Photogrammetry and Electronic 
technology, the measurement, using the Close-range 
photogrammetry methods with stereo pair to identify and match 
the 3-Demensional coordinates of the objects in the scene, is 
more and more applied in the fields of the modeling of 3- 
Demensional city, computation vision, industry metrology, 
digital mapping and so on. 
In the aerial photogrammetry, it is common to use the metric 
camera with pre-determined intrinsic parameters, and the 
geometric relationship in the image is specific. However, the 
metric camera is expensive, bulky equipment, inconvenience to 
be taken during photographing outside. Recently, the 
technology of digital camera develops fast, which capability has 
met the need of close-range photogrammetry. So, using non 
metric digital camera in this field becomes more and more 
prevalent. Compared with the common metric camera, the 
intrinsic parameters of the usual non-metric digital camera are 
uncertain in advance. The digital camera has many advantages 
to obtain image: an error will be introduced when we flatten the 
film in common metric camera but not in digital camera; its 
images can be obtained fast and safely and needs no 
development; the camera is solid, small bulk and light-weighted, 
and it has strong adaptability and fine flexibility and 
maneuverability during the photography. On the other hand, 
disadvantages also exist in the digital camera, such as the 
distortion. The digital camera usually has larger lens distortion, 
which leads to the result that the principal points can’t coincide 
with the geometric centre of image. The CCD array also has 
distortion and the image axes are not orthogonal sometimes. All 
those distortions must not be neglected, so the procedure of the 
camera calibration is complex and should take many factors 
into account. 
Camera calibration is a critical part in 3-Demensional 
measurement, and its result will affect the measurement 
precision directly. The objective of stereo camera calibration is 
to estimate the internal and external parameters of each camera. 
For non-metric camera, the lens distortion plays an important 
part in calibration, so the corrected aberration cannot be ignored 
during the calibration. Therefore, another aspect of calibration 
is to compute the aberration coefficients. 
What is Camera calibration? Camera calibration is to identify 
the camera’s posture during the data acquisition process, 
including focal length f, as the principle point coordinate (uO, 
vO) and various aberration coefficients. Camera calibration is a 
critical part in 3D measurement. Measurement accuracy is 
based on calibration result directly. 
After a period of development, the researchers have present a 
variety of calibration methods. Such as, the traditional 
calibration method which needs calibration object, and the self- 
calibration needs no calibration object. 
At present, although self-calibration has its own superiority, its 
accuracy is not satisfactory. The traditional calibration has 
developed for a longer time, with higher precision, especially 
three-dimensional calibration, which accuracy has been able to 
meet a variety of needs. However, the traditional calibration 
requires high accuracy calibration object. It is difficult to use 
this method widely. So, the planar calibration comes into being. 
Generally speaking, compared with the accuracy based on 
three-dimensional calibration, the accuracy of two-dimensional 
calibration is lower slightly. There are several problems in 
three-dimensional calibration, such as expensive cost, 
inconvenience to carry. Because of the various deficiencies of 
the three-dimensional calibration, the camera calibration based 
on two-dimensional plate has been gain favor, and calibration 
algorithms in plate calibration have become a hot research in