LINE PHOTOGRAMMETRY WITH MULTIPLE IMAGES 
Author: Dipl. Ing. Holger Zielinski 
Institution: Dept. for Photogrammetry 
Address: The Royal Institute of Technology 
5-100 44 Stockholm 
Country: Sweden 
Commission Number: III 
ABSTRACT 
A method for the calculation of 3D point coordinates from the combination of 3D straight lines, called line 
photogrammetry, will be presented. It is partly based on already existing theory. The 3D straight lines are directly 
calculated from non homologous points identified in multiple images by manual registration. Four parameters are 
used to define a 3D straight line. Space lines do not in general intersect due to errors in orientation and 
measurements. The solution used here is to include an intersection constraint into the least squares adjustment or 
to find a point with a shortest distance to the lines. For the tests, two buildings are measured in aerial photographs 
by using both stereo and line photogrammetry, and geodetically as reference. The evaluation of the results showed 
that line photogrammetry has the same or higher precision compared with stereo photogrammetry. More 
extensive tests need to be done, before this statement can be generalized. 
Key words: precision, 3-D, features, multi-image 
1. INTRODUCTION 
In digital photogrammetry, it is already possible to do Mulawa and Mikhail [3] expanded the method in such 
  
the whole image orientation fully automatic. Even the a way that more general objects like circles, ellipses or 
generation of digital elevation models has reached a splines could be used as linear features. They made the 
high degree of automation. The majority of methods point that this method can be used as a tool for the 
for automation are point oriented. development of automatic measurement procedures. 
For map production the automatic reconstruction of The parameters of the linear features were geometri- 
the shape of man-made objects and their precise locali- cally understandable, but dependent of each other. 
sation is of importance. The corner points of a building Sayed and Mikhail [5] tested methods for automatic 
can be used to describe its shape. In a production orientation of stereo images and localisation of circular 
process these points are manually measured by an and straight linear features in 3D object space. One of 
operator. Automating this process means, that those the interesting subject mentioned was to use indepen- 
image points have to be selected automatically which dent instead of dependent parameters to describe 
represent the same corner point in object space. Here linear features. 
the well known point correspondence problem have The overall purpose of this work is to test, if the use of 
to be solved. line photogrammetry will lead to a real improvement 
Instead of describing an object by corner points, it can for large scale map updating. In this investigation a set 
also be described using lines, i.e. the line between a of four parameters defining a 3D straight linear feature 
roof and a wall of a building. Such object lines can be are introduced. The reason to use four instead of Six 
described with the help of linear features. The para- dependent parameters is to avoid problems concerning 
meters of such 3D linear features can be calculated real or numerical singularities and the advantage that 
using an arbitrary number of measured image points no additional geometric constraints have to be intro- 
describing the feature. ducted explicitly to get a solution. Another intention 
Line photogrammetry is the formulation of a direct in the theoretical part of this project is the intro- 
mathematical relation between measured image duction of geometric constraints for each separate line 
points and the parameters of a 3D linear feature. The and between several lines. A theory for 3D straight line 
advantage of using line photogrammetry instead of linear features, here also called line features or straight 
point oriented photogrammetry is, that no stereo point lines, is formulated. Furthermore test results are 
to point relation is necessary. The parameters of a presented, where this method is compared with stereo 
feature can be calculated using measured image points photogrammetry. The results from a geodetic 
form different parts of the projected 3D feature. The measuring method are used as references. 
only constraint which have to be fullfilled is, that the 
measured images points belong to the same 3D linear 2. METHOD 
feature. ; ; 
A few published works exist which combine photo- 2.1 Basic mathematic relation for a straight line 
grammetry and linear features. Masry [2] described a ; ; 
method for absolute camera orientation and Lugnani An arbitrary point on an endless 3D straight line can be 
[1] for camera orientation by spatial resection, using expressed by the parametric line equation given in 
linear features. equation (1) 
Persson [4] developed these ideas further, so that it was 
possible to calculate the parameters of a 3D straight 
line in object space directly from monoscopically mea- P=S+t*d (1) 
sured image points. 
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