CIP A 2003 XIX"' International Symposium, 30 September - 04 October, 2003, Antalya, Turkey 
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Model construction takes place on a hierarchi 
cal basis, that is to say objects can be construc 
ted from smaller components and grouped to 
form an assembly. Once a complex object has 
been created, it can be cloned or saved as a 
library component. Using a unique method of 
connectors, objects having these connectors can 
be simply snapped together to form larger 
groups of objects. This approach is particularly 
useful where a complex object appears in a 
model many times and the user needs to instan 
tiate another instance of an object at a specific 
place. 
Figure 4: 3D Point cloud by IMAGER 5003 
Conversion from 3D point data into CAD 
objects is facilitated using a range of 
specifically developed fitting algorithms which 
have been developed to be both robust and 
accurate. It is an interactive conversion process, 
as the user selects specific groups of points and 
then directs the program to automatically find 
the best fit CAD representation of this object. 
This approach leads to very swift construction 
of the model even for users new to the system. 
After doing an automatic segmentation, a semi 
automatic fitting of pipes and planes is possible 
with some interaction required. The LFM fitting 
algorithms are extremely robust to noise and 
outliers, so that they still work even if the 
quality of the points is not as high as usual, 
which may happen at certain very dark surfaces. 
Meshing is another method of processing the 
data obtained by the laser scanner. It is 
extremely useful for objects with complex and 
free form surfaces like statues or castles. 
Meshing takes the cloud of data points and 
produces a triangular mesh which closely 
approximates the surface formed by the cloud 
of points. Point clouds arriving to be meshed 
can vary immensely in density, overall size and 
surface complexity, so the meshing system has 
been designed to be able to deal with these 
variations on a totally automatic basis. 
2.4 LF Architect 
LF Architect has been developed especially for 
the generation of architectural 3D models. It 
has been written as an add-in for AutoCAD 
for the editing of data resulting from the 
IMAGER 5003 in architectural and engineering 
surveying. Like in LFM, the evaluation is 
carried out in three steps: image processing, 
control point surveying and getting the 
orientation of each scan. Orientation is achieved 
by bundle calibration with CAP or BETAN / 
NEPTAN. The orientation is a fully automatic 
process. The targets and the target numbers are 
identified by a special algorithm developed 
especially for the large files of the laser scanner. 
As the files generated by the laser scanner are 
very large, LF Architect was designed to 
generate the result automatically overnight in 
batch jobs or to export point clouds directly in 
CAD packages like AutoCAD. The output of 
the software can be a mesh, floor plans or 
special sections. Orthophotos can be generated 
directly from the reflectance images. Panoramic 
camera images can be integrated into the evalu 
ation process, thus allowing to generate 
coloured models with original surfaces. 
3. APPLICATIONS 
For houses and/or monuments it is essential 
to generate a model consisting of the actual 
structure and to generate drawings for architec 
tural purposes. For most applications not only 
geometry is enough but also reflectance and if 
possible colour information is necessary to ful 
fil requirements of architects. In order to fulfil 
three dimensional geometric measurements 
with colour information, we use two 
systems, the IMAGER for geometry and reflec 
tance measurements in combination with the 
panoramic colour camera.