USE OF DLT IN PHOTOGRAMMETRIC METROLOGY o th
ba
Zeroual I.*, Liazid A** o th
Hence,
* Centre de recherche CNTS — Arzew of obje
BP13, 01 Avenue de la Palestine Thus tt
Tel : 041 47 22 17 Fax : 041 47 36 65 Email : zerouall @mail.com a data c
** Laboratoire de recherche LTE-ENSET-Oran
B.P. 1523, El Mnaouer 31000- Oran
Tel : 041 51 43 46 Fax : 041 41 98 06 Email : ab_liazid@yahoo.fr 2 Mo:
Abstract i
eT Digital
In industrial metrology, the mechanical parts come in a wide range of sizes and shapes. Hence, the measurement process must be se
adapted. Numerical photogrammetry constitutes a great contribution to industry for certain metrological treatments. In this study, we DA P
propose an approach which allows the realization of a photogrammetric system of measurement for the control of the mechanical IA :
parts. The method uses DLT transformation (Direct Linear Transformation) between the image space and the object space. The qudd
photogrammetry treatment model developed in [1] allows the monoscopic treatment of the photographs of the object under control. bv th t
The matching by least-squares and the epipolar geometry principle are applied for the calculation of an approximate configuration of i
the block defined by the perspective beams and the subject. The final compensation uses the rigorous principle of the condition of CONNEC
colinearity while at the same time taking into account all perspectives (multi-photo). The objective of this work is to achieve a
photogrammetric system of measurement based on perspective without stereoscopic vision and to see that it is possible to direct this Analyt
system towards the treatment of blocks (adjustment) relating to a project. exploit
plate. '
Key words : Metrology, Photogrammetry analyti
whethe
Nomenclature of the t
e col
Variable Signification e Co
X,y comparator co-ordinate (plate co-ordinate) the ch
XYZ object co-ordinates require
Xo9Y oZo Co-ordinate of the perspective centre. S.
R,k Rotation and scale factor dimens
b,b,b, Component of the base
x.y Plate co-ordinate after correction of rotation LE
Pl, longitudinal linear parallax of the point ( reference) me
Ho Distance between the perspective center and the reference surface colline
PI; API; longitudinal linear parallax difference between point i / reference point N
H; AH; Remoteness of the point i - difference of distance between i / reference
B Ground Base
er Focal distance and radial distance
L, transformation parameters of DLT
ki, pi po Parameters of distortion
dk;, dp,,dp2 Value of the linear interpolation
A,B,C,D Coefficients of Bopp and Krauss
1. Introduction parts. The method used is a transformation between the image
space and the object space. The photogrammetric treatment
In industrial metrology, the mechanical parts come in a very model developed in [1] allows a monoscopic analysis of the
wide range of sizes and shapes. Three-dimensional measure- ^ photographs of the object under control. The matching by least-
ment compared with a space reference gives a good definition squares and the epipolar geometry principle are applied for the
of the object in space. The extraction and development pro- calculation of an approximate configuration of the block defined
cesses of spatial information require more and more the exploi- by the perspective beams and the subject.
tation of digital imagery. Digital photogrammetry remains ever Photography, as a source of information is intended to provide 2-2 Ec
present for these metrological treatments, making perhaps a in a convenient form information concerned with several fields The
great contribution to industry [2]. and presenting zones which overlap: of d
This study proposes an approach which allows the realization of ® the geometric field in which position, shape and dimension relativ
a photogrammetric system of measurement for the mechanical
of the object are the principal unknown factors.
—110—
