International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004
navigated themselves while there is no computer or map. They
early on used different techniques to find their roads but
technological developments made this activity more interesting
and easy in time with paper maps. Nowadays, it can be
managed by the help of special navigation systems including
integration of developing positioning and communication
techniques, digital maps, computer and handheld device
technologies. Today, these systems are used in different
applications, so navigation is entitled according to its
application area just as aircraft, marine, nautical, personal, and
car navigation etc. Although these navigation types have
significant differences because of their application dependent
constraints and purposes, way finding demand forms the core of
them (Timps et al., 1992).
In this study, car navigation considered as the basic activity and
an approach for the production navigation maps tried to be
proposed in terms of MRDB. However the system needs
systematic updates in attribute and geometric level. Although
changes in navigation conditions can be updated by using
different technologies just as Internet or radio waves, geometric
changes on the structure of road networks should be
automatically updated in the system so database for the system
should be available for update propagation. However this
database should be formed based on MRDB (Ulugtekin et al.,
2004).
Map design for navigation purposes is not scanning or
digitizing existing paper maps. While designing such maps,
usage conditions (psychological factors, external impacts, road
conditions, etc.) should be considered in addition to design
criteria. In this context, requirements for navigation map design
are determined. As a result, this process considered as a part of
small display cartography because of the technology used in
navigation systems especially for representation. This makes
the production process more complex and difficult.
4.1 Work Steps
After determining the requirements of the process
representation levels are determined for different part of roads.
Than topological relations for different representation levels are
formalized and generalization operators that will be used in the
process are selected. All representational levels are tested in
different GIS and mapping software in terms of their
consistency for the basic queries used in the navigation process,
such as finding shortest paths or optimal routes. The results of
these tests then permit the selection of the most appropriate
representation level on which the standard algorithms can be
used without any additional capabilities.
4.2 Representational Levels
Finally, desired cartography for map production should support
the purpose, provide the aims and satisfy user requirements
(Nissen et al., 2003). For example, a driver using a navigation
system on a foreign city or country wants the system to
navigate him as well as possible so system maps should display
world reality in correct scale and resolution. Especially in road
networks complex junction types should be visualized in detail.
In this context, representation of junctions, which are the most
complex parts of the road networks, is considered as key
problem and different representation levels, where single and
two lane representations of roads containing complex and basic
junction views are determined (see Figure 1). Timpf et al.
(1992), states that the existence of the multiple lanes is assumed
246
but it is not needed for locating correct exits and entrances on
road network. These different representational levels are
examined by considering different aspects just like
formalization difficulties, exchangeability among all software,
usage and design costs to get an absolute result. The city of
Istanbul is taken as the study area: Europe’s largest city
provides a challenging range of road features for consideration,
in challenging quantities.
Road network is represented by single
line. The junction is visualized by
th
Lat using a single point (node) at the
intersection of two roads. This level is
used current
generally navigation
maps.
Road network is represented by single
3 Level line. Details of the junction are
basically visualized.
Road network is represented by two
nd f5z2 7 different lines for cach direction.
2™ Level v»
m Junctions detail as
|
have as much
/ possible in this representational level.
Road networks are represented in
detail. All other representational levels
Base
Level are derived from this level or higher
levels. Scale: 1:5000.
Figure 1. Representation Levels
4.3 Data Formalization and Reasoning Processes
Data formalization should be considered as one of the most
important stage for an MRDB system, because mathematical
definitions of the spatial objects and their relations were done
using a consistent formalization language. Unless they were
defined, the MRDB system cannot cover the aim of automatic
generalization and update propagation. Different mathematical
methods as Graph theory can be used in this process then they
are expressed by using an appropriate formalization language.
Studies on formalization of the representations continue. For
example following relation definitions were written by using
predicate calculus.
Vk.y (Connect(x,y) -» On((StartPoint(x) VEndPoint. (x)),y) A
(x7)
V&,y (Intersect(x.y) -» (Zn(On(n,x) A On(n,y)) A nz (StartPoint
A EndPoint))
The first of these statements means that if a road x is connected
to road y, the end or start point of the road x is on the road y.
The second means that if a road x intersects road y then there is
at least one point, a node, on both of the roads but this point can
not be a start or end point.
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