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6 Analysis of field-of-view impact
6.1 Technical approach
Drawing up technically sound field-of-view analyses, the methodological core of the
field-of-view impact study, basically consists of two procedural steps. Firstly, a digital
3D model, which must contain three dimensional data on the topographical situation,
on the object being studied (in this case, the “Verkehrszug Waldschlösschen”) as well
as modelling essential landmark structural elements within the area under investigation,
has to be made. Secondly, photographs taken under satisfactory visual conditions are
required for the field-of-view analysis. These photographs are to be made with a focal
length of about 50 mm to simulate human perception to the greatest extent possible
(source: jochen rütschlin’s exposé; http://www.jr-x.de/digitalfotografie/fototechnik.
html). The photographs are then superimposed on perspectives of the 3D model that
are produced in the same focal length as the photographs. In this manner it is possible
to “overlay” photographs and 3D perspectives so as to create realistic visualisations of
the proposed thoroughfare within the current landscape.
Step 1: Creating a fragmentary 3D city model
Various data made available by the State Surveying Office of Saxony was used as the
basis for creating the digital 3D model of the study area. Ground points in a regular 5 x
5 metre raster generated from an aerial laser scan were used to create the terrain geo-
metry. A point cloud made of non-ordered laser surveying points with high-resolution
ortho-photos and building contours were layered upon one another in order to create
an exact reconstruction of the relevant building geometries necessary for the alignment
of the perspectives. The laser survey points from an aerial laser scan thereby create a
non-ordered raster with an approximate grid size of 1 x1 metre and do not distinguish
between different elements such as trees, bushes, flocks of birds, buildings and ground
points. In order to recreate the buildings, their contours are extruded upwards through
the terrain geometry to the height of the appropriate points generated by the aerial
laser scans. The aerial photographs, as well as the 3D data necessary for the creation
of the exact geometry of important buildings or landmark structures, were also made
available by the State Surveying Office of Saxony.
The 3D city model is thus composed of three elements:
a. the digital terrain model
b. the buildings relevant to the alignment of the perspectives, as well as landmark
elements
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