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Georgopoulos, Andreas 
  
the buildings was derived from old amateur photographs and the models of the buildings was produced as 3-D solids 
using an appropriate architectural design software package. The locations of the destroyed buildings and the outline of 
their basement were also determined from old aerial photographs. In order to be able to superimpose the model of the 
buildings on top of the model of the topography, the TIN model of the topography was modified to include the outlines 
of the basement as breaklines. Finally, the model of the settlement was composed and was ready to be rendered in order 
to be visualised from different viewpoints in a CAD environment. The above described methodology is illustrated in 
Figure 1. 
The evolution of existing technological environment for visualising three-dimensional space has three significant 
advantages both in software and hardware. The first one allows users to model three-dimensional spatial objects in a 
sophisticated way. The second one integrates data having different structures (vector or raster). The third advantage 
provides users with tools to perform complicated analytical transformations on spatial data in a very reasonable 
processing duration. More specifically, existing software platforms are supporting user’s perception of the real world as 
solids, composite solids, surfaces or wireframes and translate them into graphical objects (i.e. polylines, arcs, faces or 
meshes etc.), having three-dimensional properties. In addition, existing software enriched with sophisticated analytical 
methods, allows users to perform photogrammteric compilation, geometric transformations, image processing (i.e. 
resampling, radiometric corrections etc.) and also provides them with powerful editing environments. Furthermore, the 
core of the existing visualising software is characterised by the depth of the visualisation media such as oblique views 
or animated movies in appropriate realistic form. These views are created by rendering the three-dimensional graphical 
objects or by draping images on three-dimensional meshes. Their realistic character is provided through extended 
libraries of digital motives for “dressing” the three-dimensional objects during rendering and through the simulation of 
the effect of natural illumination -by creating shades- and various meteorological conditions (i.e. fog, rain, snow etc.), 
as it is suggested in a relevant study (Nakos and Tzelepis, 1998). 
3 TECHNICAL DETAILS OF APPLICATION 
As mentioned above, the aim of this application was to try and represent a destroyed traditional settlement. This 
application was based on the research carried out within a diploma thesis (Anastassopoulou and Kappatou, 1998) at the 
Department of Rural and Surveying Engineering of National Technical University of Athens. The small village of 
Agios Efstratios, the only settlement on a small island of the North Aegean, has stood there for centuries. Built 
according to the traditional Asia Minor architecture the approximately 500 stone houses covered a hill, thus forming a 
remarkable sight. On top of the hill a byzantine castle served as the only refuge of the population against the pirates of 
the past. In February of 1968 a terrible earthquake destroyed most of the houses and the population was forced to 
abandon the settlement, as the military government decided to build a "temporary" and ugly village on the lowlands 
around the small port. This village serves the lodging needs of the population up to the present day. 
Today the local community wishes to revive the traditional settlement and this application aims at its three-dimensional 
visualisation, in order to support this task. For this purpose, several data were sought. Aerial photographs before the 
earthquake, amateur photographs of the village for the period 1940-1970 and a recent survey of the area, carried out in 
1995, were the main data sources. 
Firstly the Digital Terrain Model of the area was produced using the recent survey of scale 1:1000, assuming that over 
the years the terrain has had minor or no changes at all. The plots available contained contour lines of 1m interval and 
numerous dense spot heights. These plots were scanned with a AO size drum scanner and the contour lines and the 
elevations were digitised. Subsequently, the vector plots were geocoded in a CAD environment with the help of several 
registration points. In order to produce a handy DTM the vector information was then processed with the help of a 
suitable software in the same environment. Breaklines were added where necessary, in order to achieve the optimum 
representation of the terrain, especially in the case of strong terrain undulations. The processing with QuickSurf yielded 
a DTM with 3D faces, ready for further processing and rendering. 
Secondly the 1:30000 aerial photographs of the year 1960, taken prior to the earthquake, were the only source available, 
in order to extract the urban web of the settlement, as well as the exact position of most of the buildings. This was 
considered necessary in order to represent as well as possible the destroyed settlement. The stereopair was relatively 
oriented and levelled using the elevations of the coastline. The result of this action was the planimetry of the old 
settlement and the outlines of the old buildings. This product was subsequently suitably scaled with the help of the 
digitised 1:1000 plot. 
Using information from the aerial stereopair and from the amateur photographs the 3 -D reconstruction of some typical 
houses was determined. This process was realised using AutoCAD and a specialised software for geometric 3-D 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B5. Amsterdam 2000. 287