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DESIGN AND IMPLEMENTATION OF A WEB-BASED APPLICATION 
FOR THE VISUALIZATION OF LARGE SCALE PHOTOGRAMMETRIC 
AND CARTOGRAPHIC DATA 
. = og - b 
Maria Spanaki ^, Lysandros Tsoulos 
" Surveying Eng. MSc Geomatics — PhD Student, " Assoc. Professor NTUA 
Cartography Laboratory, Faculty of Rural and Surveying Engineering 
National Technical University of Athens 
9 H. Polytechniou, 157 80 Zographou Campus, Athens, Greece 
spanaki@mail.ntua.gr, lysandro@central.ntua.gr 
KEY WORDS: Photogrammetry, Cartography, Web-based, Standards, Open systems 
ABSTRACT: 
The objective of this paper is to show the way multiple source data like aerial photos, maps and descriptive information are combined 
and amalgamated to form an Internet or Intranet application. The visual outcome is a large scale, precise and detailed image/map 
displaying the interiors of buildings in a layered fashion, enabling the user to interact with the objects shown on it. Scalable Vector 
Graphics - SVG is an XML language for the encoding/representation of two dimensional vector data, especially designed for 
integration with other web standards. SVG provides those basic structures, which are needed for map generation and overcomes the 
disadvantages inherent to bitmap images displaying spatial data. In the domain of spatial data, SVG constitutes a new powerful 
standard for visualization and has a great potential along with other XML encoding languages like Geographic Markup Language - 
GML, Extensible Stylesheet Language Transformation — XSLT and Cas Cading Style Sheets — CSS for the development of Web- 
based applications utilizing open source software and standards. This paper elaborates on the way SVG data is generated from 
existing cartographic and photogrammetric sources and the use of scripts in order to provide the user with interactive and animation 
capabilities, resulting to a comprehensive and user friendly map in the Internet. More specifically, photogrammetric data is translated 
into a neutral format and subsequently to SVG graphics with the utilization of tools that implement this conversion that is carried out 
separately for the point, line and polygon data, which are subsequently combined into a uniform SVG image. The Graphics User 
Interface specifically developed for this application, enables the user to select a building from the specified area [i.e. a University 
campus], to virtually *enter" into the interior of the building and to visualize structural and other information relative with the use of 
the office space [libraries, laboratories etc] along with the corresponding data for the phone number, IP address etc. 
I. INTRODUCTION 
providing the end user with high graphic quality results along 
Photogrammetry and Remote Sensing are two major scientific with interactive capabilities. Emphasis is given to the 
domains enabling the collection, analysis and distribution of exploitation of capabilities that SVG provides and detailed 
huge amounts of geospatial information. Such information in references are made to specific elements, attributes and design 
the form of aerial photos, satellite images, orthophotomaps, and ideas implemented bchind what user sees. 
topographic maps is essential to be easily exploited in a web 
based application environment. Since XML technologies are 2. TRANSFORMATION OF VECTOR MAP FILES TO 
gaining wide acceptance and are incorporated as standards in SVG 
software products, a need for utilizing photogrammentric and 
remote sensing data in a new fashioned way is evident. Since SVG was introduced a few years ago, considerable efforts 
This paper elaborates on a case study concerning the way have been made in the direction of providing users with format 
photogrammetric data can be easily transformed and combined conversion techniques, tools and software programmes for the 
with other source data to build a web application based on the transformation from vector proprietary formats to the non- 
Scalable Vector Graphics - SVG format. The aim of the study is proprietary SVG format. There are many such tools available on 
the development of a map application on the web - covering the the Internet giving users the opportunity to convert vector data 
area of a university campus - that enables the user to interact used in GIS applications to SVG web graphics. The major part 
with floor layered information, which contains construction of GIS data is stored in proprietary vector formats like shape 
details just as shown in a vector file format like dwg or dgn. The files or cad files, so the need for tools that convert these files to 
basic geometric constructs like lines, points and polygons are SVG should be quickly fulfilled (Carto:net, 2003). One of these 
extracted from aerial views using fundamental photogrammetric tools - utilized in this case study - is the CAD2SVG converter 
methods and contain information about the outline of campus’ by Savage software. The CAD2SVG converter enables the 
buildings in real world coordinates. The next phase refers to the conversion of DWG and DXF files to the SVG format. This can 
transformation of all other existing drawing data at the floor be applied to single files or directories. The same conversion 
level in a building to the same coordinate system. The can be also applied to DGN files, through the DGN2SVG 
transformation of vector file formats to SVG graphics is converter. In both cases, using the option of compressing the 
implemented using open source software tools available on the SVG files to svgz format, the converter compresses the output 
Internet. Since SVG has no compatibility problems with other which typically results in a file savings of 8095-9096 over the 
web standards and raster file formats, the development of the original file size. In addition, when “smart origin" is selected, 
final application is carried out in a very fast and efficient way the converters automatically normalize the origin of the file, so 
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