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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004 
  
GEOGRAPHICAL INFORMATION SYSTEMS AND DIGITAL MODELS 
Aiman Malla Houech Al Mahmoud Ph.D. 
Public Authority for Housing Welfare, Department of Planning, Kuwait - aiman_almahmoud@yahoo.com 
  
Commission ,PS WG IV/6 Landscape Modelling and Visualization 
KEY WORDS: GIS, DBM/DTM 
ABSTRACT 
This paper discusses problems, connected with description of technological processes in manipulating and using of existing data 
within the GIS. In this context, 1 will also deal with the accompanying stages of creating Digital Building Models 
(DBM).Furthermore, I will also discuss problems and errors faced due to the natures of the automation processes. Finally, I will also 
highlight the role which the contemporary Digital Photogrammetric Technologies play in the information systems for urban planning 
and management. 
Introduction 
The automation of the generation of 3D city models as required 
by many users of Geographic Information Systems has become 
a major focus of photogrammetric research in the past few 
years. Starting with 2D image processing techniques, 
researchers did soon turn towards 3D approaches like grouping 
features matched in multiple images. The automatic extraction 
of parametric and prismatic building models from digital 
elevation models generated by photogrammetric techniques or 
airborne laser scanning . 
The best and must complete cartographic products can be 
obtained by photogrammetric survey at a proper scale, a correct 
scanning of existing cartography submitted to a robust 
georeferencing process, can give acceptable cartographic 
products for GIS applications. 
Problems of manually managins 3D objects representation 
Digital orthophotos in combination with GIS are a suitable 
instrument for input data for changes in mapping rapidly 
growing cities. It is expected that in the 21% century, more than 
70% of earth inhabitants will live in cities. Therefore accurate 
mapping of cities in digital orthophotos is very important. There 
are systems for digital orthophoto, which are not present as 
objects until now such as buildings, bridges or highways as a 
3D. Therefore middle scale (1:5000 -1:10000) orthophotos of 
urban areas show disturbing geometric errors in the form of 
displacement and double mapping [1]. 
Erroneous pixels in common digital orthophotos exist in excess 
of 8%, depending mainly on building density and height .This 
causes serious problems for further applications such as data 
overlay, 2D coordinate measurement or 3D visualization. This 
paper presents a method for accurate mapping of 3D objects in 
digital orthophotos. It is based on image separation and 
independent rectification of terrain and building areas. 
The proposed solution for accurately mapped orthophotos calls 
for requires the following processes : 
* Digital building model. 
* Building orthophoto computation. 
* Terrain orthophoto computation. 
481 
The digital building model determine the shape of each building 
and is required for the subsequent process of building 
orthophoto. Since conventional orthophotos system can hardly 
model building surfaces and is not concerned with hidden 
surfaces, an algorithm has been developed for this purpose. The 
result of this process is an orthophoto of all buildings. 
Digital Building Model (DBM) 
There are many types of 3D-objects visible in aerial images. 
Natural objects such as trees will not be considered in this work 
.An overview of buildings and their representations is given in 
Fig.1. 
Fig.1. Overview of buildings and their representations 
A flexible solution to model this types of objects is boundary 
representation. ~~ This technique uses geometric to describe 
objects boundaries. It is sufficient to choose triangles and 
quadrangles as geometric . Beside the geometric shape which 
the building model represent, it also attribute information for 
each geometric primitive. The digital building model 
distinguishes between primitives that are 
visible in the orthophoto (e.g. roof) and invisible(e.g. wall, 
vertical element, etc). 
Methods of data acquisition for building digital model 
(DBM) 
Currently data capturing for building models usually is done 
manually on analytical or digital photogrammetric stereo- 
digitizers. In procedures, sufficient to ^ automated data 
acquisition, applying digital techniques are still under