Bürger, Thomas 
A great amount of research is still needed to make the relatively new technique of close-range photogrammetry a suitable 
tool for the reconstruction of these objects. Recent approaches that link photogrammetry with digital image processing 
hold a great potential that has not yet been fully realized. 
This paper explores the individual steps of a photogrammetric as-built-documentation and aims to optimize the procedure, Z 
The documentation process is based on the assumption that universally accepted industrial standards of shape and position 
of typical plant elements have been met. This knowledge has been applied to the orientation phase as well as to the 
reconstruction phase of the documentation process. The optimization lead to a prototype close-range photogrammetric 
system for as-built-documentation of process plants. 
As a new documentation tool this digital photogrammetric system has been made compatible with existing CAE tools that 
demand certain CAD-model structure and data management facilities. 
It is the object of digital photogrammetry to find a way to deal with data acquisition and data interpretation in a highly 
automated way. This paper presents tools that support actually an interactive reconstruction with standard data of process 
minin 
plants. Using these tools the design of an automatic as-built-documentation system should be around the corner. Initial 
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2 RECONSTRUCTING PLANT ELEMENTS IN ORIENTED IMAGES (e.g. 1 
Actually two different kinds of tools exist to perform photogrammetric as-built-documentation: Two | 
plane: 
1. Tools based on CAD-systems with highly optimized modelling capabilities. Those systems are still lacking a number | plane 
of photogrammetric measurement features. Some systems allow only “modelling on top of the photo". I jd 
is obt 
2. Digital photogrammetric systems permit the measurement of some (not yet all) features needed to model the plant Houg 
elements. The data of those systems must be imported into CAD 
-Systems in order to perform the plant-modelling. 
In general the reconstruction of process plants and its components always consists of two steps which should be ideally 
combined into one interactive system: 
Reconstruction — Feature-Measurement + Modelling. 
2.1 Feature-Measurement 
The components of process plants are typically pipes, valves, pumpes, elbows, flanges, etc.: Standardized components, 
hardly to be measured by single, homologous imagepoints. The features to measure are points on lines, edges, points on | NS 
circles or directly circles, cylindric and conic forms. The following methods measure those features: | 
First of all the epipolar-line method is an important tool in as-build measurement of points on arbitrary edges. 
     
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Figure 1: Measurement of point on flange-edge cour 
The location of a point on a flan 
ge-edge relativ to the pipe’s centerline defines position and shape of the flange. In this 2.2 
article we will see that methods 
with a higher accuracy are not neccessary in this case. 
The : 
Straight lines (e.g. body edges, steel beam edges) are initially identified in space as the intersection of two planes (Fig. 2). this | 
If more than two images and more than two points per image are used the position of the line in space is found by exam 
  
  
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B5. Amsterdam 2000.