International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004
conditions and checks were implemented in order to satisfy the
required rules by the highway agency. The component ‘Road
Event' was also implemented subject to similar modifications.
With the defined method Detecting Alignment Elements of
‘Linear Geometry’ geometrical component of the proposed
conceptual data model was generated. Topology component was
implemented as proposed in the conceptual data model, which is
shown in Figure 3.
Figure 3: Implemented Geometry and Topology Components
The defined method Dynamic Reference Transformation of
‘Road Event’ was generated using ArcObjects. Through
compatible programming languages such as Visual Basic,
Visual C++ and Delphi, it is possible to create or add user-
defined objects to a database, which operate directly with
ArcObjects. As the sample data was dependent on the link-node
linear referencing system, this methodology was used for re-
transformation during designed interfaces. (Pfannmóller,2001)
‘Road Event’, described in the conceptual data model, was
obtained using the program and existing interfaces. In addition,
‘Road Event’ object information identified at vertical sections
were also realized using the methods Detecting Alignment
Element and Dynamic Reference Transformation. The height
information was already existed in the provided data set. The
implementation results are illustrated in Figure 4.
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Figure 4: Implemented Geometry and Topology Components
The cross-sectional design information, which was predefined
as the (q, h) reference system, was also implemented. Some of
the defined integrity constraints in the proposed conceptual data
model were performed using existing “validation rules” in
“geometry network” of ArcInfo8™. Others were introduced
into the system by means of triggers, which will be introduced
below. An example of the validation rules used in the system
The maintenance of complex relationships and validation of
complex rules are often needed to be defined externally, due to
lack of realization of the encapsulation concept. In order to
define these, triggers are in the Oracle database management
system. A trigger is a method which is invoked whenever a
specified object or attribute is inserted, updated or deleted.
Ideally, it should be possible to invoke the full range of GIS
methods within a trigger and it should be possible to cause the
current transaction to be rolled back if an invalid condition is
found within a trigger. Procedures are started explicitly by the
user, by an application or also a trigger. These are procedures
written in PL/SQL, Java, or C that execute ("fire") implicitly.
With the releasing event it concerns one or more Data
Manipulation Language (DML) operations (insert, update and
delete). The connectivity rules, redundancy controls, integrity
constraints were performed using this method.
5. Conclusion
In order to increase the efficiency and to provide data
integration, this study considered a progressive approach
appropriate to the conceptual data modelling requirements of an
entire highway agency. The designed generic conceptual data
model presents a considerable departure from traditional
network-data models in order to comprehend the user
assessments. With the Dynamic Reference Transformation
method; i) decomposition of spatial and non-spatial information
is realized. This increases the stability and simplifies the data
maintenance, ii) thematic data is independent of geometrical
displacements such as; realignment and error corrections,
iii)multi-dimensional road information is mapped into the
conceptual data model without redundancy, iv)no pre-defined
methodology is required, users are frec to apply the most
appropriate methodology from their point of view. This is
because every one-dimensional reference system is transformed
dynamically and stored in a three-dimensional coordinate
system, v) re-transformation into 1-D is modelled and supported
by means of interfaces, vi)stochastic properties of linear
—.1 elements and (/, q) parameters are available, vii)full integration
i is realized with other data acquisition techniques where
information is referenced 3-D, viii)existing data with multiple
referencing systems is fully integrated, ix)due to the minimal
data acquisition requirements, a more economical solution is
provided compared with other techniques, x)the proposed
technique is independent of any software vendor or platform.
This generic approach ensured; i) the abstraction and
decomposition of geometry, topology and non-spatial data, ii)
the transformation and integration of multi-dimensional data in
3-D, iii) the support for multiple topological representation and
various abstraction levels, iv) the non-planar topological model,
v) the incorporation of metadata, involving integrity constraints,
history and quality. The effectiveness of the developed concepts
was tested on two different projects. According to the results of
the conducted projects, this approach is explicitly beneficiary
when compared with the traditional road data models.
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Program:
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Gielsdorf.
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