6A-2-3 
Described methods allow not only representation of any object in 
3D global co-ordinate frame but also to determine object’s 
properties like colour, geometrical form, size and relative distance 
to the MMS system or other objects in the scene. 
4 MODELLING WITH VRML 
VRML is an ISO standard file format for describing interactive 
3D objects and worlds. It is designed to be used on thdntemet, 
intranets, and local client systems and is also intended to be a 
universal interchange format for integrated 3D graphics and 
multimedia. VRML is also capable of representing static and 
animated dynamic 3D and multimedia objects with hyperlinks to 
other media such as text, sounds, movies, and images (The 
VRML Consortium Inc., 1999). VRLM provides a convenient 
language for generation of 3D scenes from georeferenced data, 
with the added advantage of conceptual simplicity, platform 
independence, and wide range of free software. The capacity of 
3D visualisation and the possibility of linking different data 
sources makes VRLM a very attractive tool for creating an 
interface into databases and information system. Moreover, 
attractive fly- and walk-through capabilities offer fascinating 
possibilities of exploration of real environments, planning, 
modelling, hypothesis generation, confirmatory data analysis and 
decision generation, and many other concepts. 
Figure 5. Billboard surfaces - simplified representation of 3D 
objects. 
All objects were linked to each other and combined into worlds. 
For example, the billboard nodes were linked and grouped using 
nodes Inline and Transform (Fig 6). The Inline node combines 
local models into a global world model and the Transform groups 
object into the worlds with common transformation parameters. 
I 
There are several ways in which to present 3D reality with help of 
VRLM tools. Some authors like Gruber et al (1996), Steinfort 
(1998), Hole (1998) Gulch (1998) approaches realism by 
rendering 3D CAD models with a real life images e.g., images of 
facades, streets, or pavements. Such representation is called 
Visual Reality and has many advantages. Perhaps, the most 
important one is that it almost perfecteflect reality. However, in 
a situation where the model becomes more complex even using 
compressed real life images a large graphic (video) memory is 
required. Proposed idea in this paper focuses on symbolic 
representation. In modelling of a physical environment real-world 
characteristics were approximated by geographical symbols of 
real objects. Such representation does not require big graphic 
memory, it is easy to understand and can be viewed on standard 
PC computers. The pseudo realism is achieved by hyperlinking 
symbolic objects to real-life images captured by MMS. 
A standard object type like houses or trees may be selected from a 
predefined set of alternatives according to one or more fields in 
the GIS data record. The houses can be represented as symbols 
corresponding to villa, supermarket, block etc. But in this project 
geographical objects representing road signs, trees and houses 
were created manually and defined as billboard nodes (Fig 5). A 
node corresponds to a basic unit of VRML that contains data for 
the scene. A billboard node is a 2D surface that rotates around a 
specific axis so that it always faces viewpoint. A billboard is a 
very efficient way (small file size) to add realism to a scene. 
Typically the billboard nodes used in this approach consisted 
from sub nodes like the axisOfRotation node, shape node, 
geometry node, appearance node and grouping node (Hartman 
and Wemecke 1997). 
Figure 6. Example of linking the billboard node to the world 
(scene diagram for a group hierarchy). Empty circle corresponds 
to a non-grouping node. Filled circle corresponds to a grouping 
node. 
5. HYPERLINKING TO OTHER DATA SOURCES 
Geographical objects like trees, buildings, signs and roads were 
measured from stereo georeferenced images and transformed to 
VRML scene according to GIS parameters for each node in the 
scene. This means that each object location was described by 
geographical co-ordinates, while height and material 
characteristics, such as colours or texture, were designed 
manually corresponding to properties of the object in the real 
world (Fig 7). 
Figure 7. 3D virtual world created from object measured with 
MMS. The model includes original image of the real world.