Gis data and spatial models pdf

Realisation of "true" 3D GIS spatial system needs a lot of effort, and the process is taking place in various research centres and universities in some countries. The development of spatial data modelling for 3D objects is the focus of this book. The area of application includes natural systems - such as biology environ mental and geo-sciences, physics, and chemistry - and synthetic systems such as electronics and financial and economic systems.

The discipline is a bridge bet ween 'classical' computer science - logic, complexity, architecture, algorithm- mathematics, and the use of computers in the aforementioned areas. The relevance for society stems from the numerous challenges that exist in the various science and engineering disciplines, which can be tackled by advances made in this field. For instance new models and methods to study environmental issues like the quality of air, water, and soil, and weather and climate predictions through simulations, as well as the simulation-supported development of cars, airplanes, and medical and transport systems etc.

Paraphrasing R. Kenway R. Kenway, Contemporary Physics. With the use of statistical analysis techniques, a comparison was made by the authors as to which organisations have the greater level of GIS maturity.

More implementers are created. In the first stage, a module of business process GIS i. In the second stage, top management funding and policy guidance are secured.

The objective at this stage is to build a robust, over-arching framework to guide GIS development in the organisation later on. In the third stage, the emphasis of development of the corporate GIS is shifted from building the centralised entity to building GIS capabilities in business units.

These are based on the over-arching framework introduced in the second stage. Table 1 summarises the findings on organisational stage management of the computing resource and highlights the similarities across each of the models.

Figure 4 shows the key elements described in the assimilation of stage models Table 1 , but extends these taking into account the infrastructural aspects of SDI and the external influences. An SDI initiative within a country tends to occur at the national level and this will influence local deployment.

Therefore, Figure 4 shows two additional columns, which deal with the specific SDI deployment issues and the external influences. In this early stage, it is crucial for the GIS to have a champion, preferably at a high level, whose reach and influence is more significant. Likewise the awareness of an SDI must be built and this can draw on national awareness campaigns. From this and the fact that there is a drive to attract a critical mass of users to the GIS, it experiences a sharp increase in costs and new employees.

The outcome of this is an increase in activity and business, which leads a saturation of GIS development capacity. The growth phase must be sensitive to this powerful actor the existing infrastructure and pay attention to any emerging tensions. Implementation tactics are required to resolve or overcome these varied resistances. In Stage 3, Control Stage, planning and control procedures are usually enforced by a steering committee. Also, from the hiring of specialised employees or Systems Analysts, functional departments evolve and new hierarchies emerge.

At this stage, implementers move to a training and support role, from which further implementers are produced. Spatial data standardisation is a key aspect of an SDI and these standards are typically defined at the national level. It is imperative that adherence to spatial data standards is monitored, ensuring high data quality.

There a number of reasons for this. The moving of Systems Analysts to various functional departments provides the first GIS cross-departmental link. Building on the planning and control introduced in Stage 4 and the communication taking place between hitherto-diverse departments, the firm reaches a period of stability, whereby growth in employee recruitment and new technology is balanced with efficiency and is evenly-managed.

Infrastructure is seamlessly reusable and is only visible through its use patterns, as it cannot be deconstructed from its use. For example, spatial data that is separated from a planning application ceases to be infrastructural and is therefore redundant. In the stability phase the spatial data must become embedded within multiple applications and in doing so it becomes an infrastructure.

This becomes complex as many spatial oriented government activities span multiple local authorities, so these inter-organisational processes become an external factor. Conclusion GIS has been used extensively within local government and the SDI initiative, by their nature add complexity to the deployment issue.

Many countries have undertaken SDI initiatives, which tend to be central and national in focus. The main motivation for this paper centres on the lack of clear guidelines for adoption of GIS and SDI at a local level.

Particularly, as GIS is widely adopted in Government and within local authorities already. There is a clear interplay between GIS and SDI, so having distinguished between these; the paper highlights key characteristics that require different deployment considerations.

The stage model literature was reviewed and the assimilation is presented as a basis for an extended SDI deployment model. This assimilation clearly indicates that GIS stage models exist, but these do not necessarily imply that SDI deployment will follow in the same manner. This paper makes a contribution by providing a prescribed road map that aids in the deployment of GIS and SDI within local government.

It should also be useful to local authorities, who currently have limited GIS technology utilisation. References Campbell, H. GIS and Organisations. London: Taylor and Francis.

Chan; T. Ciborra ed. Oxford University Press. Craglia, M. This procedure running on SocetSet, Leica was applied to reconstruct the centrum of Enschede Figure 3, middle.

The 3D objects of these two procedures were also successfully imported in Oracle Spatial by the following steps: a Creation of features and categories. The query can be performed with respect to the features defined in GeoGraphics.

If a feature e. Rendering of thousands of polygons can be easily avoided. The user is expected to have excellent skills in both systems, i.

Data Structuring. The concepts implemented in both systems follow closely the OpenGIS specifications, i. Nevertheless, the implementations are still not completely application independent. The test has revealed that one significant part of the information about the geographic feature is maintained at a database level.

However, the notations table names, columns, object definitions have very specific application- oriented in this case MicroStation meaning. As was mentioned before, despite the lack of a real 3D object, description of 3D data is possible in the geometry types of Oracle spatial.

The Z value is maintained together with the X,Y values, i. Stoter and Oosterom propose new values of the mdsys. This approach will reduce considerably the size of the array, which is a critical consideration in maintaining 3D data. The support of parameters to describe physical properties of 3D objects is still missing.

For example, the colour of a polygon in rendering mode is selected with respect to the colour of the line. Data Analysis. Tools to perform spatial operations 2D topology or operators using the geometric model of Oracle are provided but they operate with only X, Y coordinates.

Some of the operations accept X, Y, Z values but the computations are purely 2D. Data Manipulation and Visualisation. It is well known and frequently commented that the amount of data to be visualised in 3D increases tremendously and requires supplementary techniques LOD, on-fly simplification, etc. Having 3D data stored in a database, the user has the possibility to extract only a limited set of data e.

For example, the whole Vienna data set is loaded for about 40 minutes, while one building comes up for fractions of a second. Locating, editing and examining a particular object also becomes quick, simple and convenient. Indeed, the elements that can be edited correspond to the geometry representation in Oracle Spatial.

The editing operations are restricted to the defined objects in our cases polygons and their vertices. For example, a shift of one vertex will change the vertex of the selected polygon.

Moreover, many of the parametric shapes spheres, cylinders, cubes and all types of extruded shapes provided by MicroStation cannot be posted to the database, i. Among all, 3D analysis and other related issues topological models, frameworks for representing spatial relationships, 3D visualisation are mostly in the focus of investigations. Topological model: The topological model is closely related to the representation of spatial relationships, which are the basis of a large group of operations to be performed in GIS, e.

Several 3D models have already been reported in the literature. Each of the models has strong and weak points for representing spatial objects. Carlson proposed a model called the simplicial complex. The simplex is the simplest representation of a cell. He uses the simplexes to denote spatial objects of node, line, surface, and volume. The model can be extended to n-dimensions.

The model maintains nodes, arcs, edges and faces that are used to describe four types of features named points, lines, surfaces and bodies. Compared to the simplex approach, 3DFDS has fewer restrictions on the objects, e. Furthermore, some spatial relationships are explicitly stored, i. The model belongs to the group of Boundary representations B-reps. Pigot developed a 3D topological model based on 0,1,2, 3 cell, which maintains an explicit description of relationships between cells.

He proposed an integrated data model for 3D GIS i. Moreover, the author developed the Tetrahedron Network TEN data structure that is based on simplexes.

For example, De la Losa maintains the relationship arc-faces and introduces a strict ordering of faces. Zlatanova discusses some aspects of the data structuring and 3D visualisation with respect to data query over the Web. The proposed data structure lacks the 1-cell in order to improve the performance of the system.

Consensus on a single 3D topological model is not achieved. A topological model appropriate for one application can be completely inapplicable for other application. Therefore Oosterom et al propose maintenance of multiple topological models in the database as the rules and constraints of each model are explicitly represented in a metadata table.

Functions have to provide consistent migration between the topological models as well as to the geometric model. Formalism for detecting spatial relationships: OpenGIS consortium has adopted two frameworks to detect spatial relationships known as Egenhofer operators and Clementini operators based on the 9-intersection model see Egenhofer and Herring, , Clementini and Felice, Although the topology is considered the most appropriate mechanism to describe spatial relationships, the study on other mathematical frameworks continues.

Billen et al propose another framework i. The Dimensional model allows larger variations in the grouping of spatial relationships compared to the 9- intersection model. Data Presentation: Advances in the area of computer graphics have made visual media a major ingredient of the current interface in the communication and interaction with computers. Many viewers and browsers as stand-alone applications and plug-ins have been developed to quickly visualise and navigate through 3D models for a variety of applications.

New algorithms and implementations are reported daily. The design criteria, however, are fast rendering techniques based on internal structures rather than utilisation of database representations. The first attempt to disseminate and explore 3D data, i.

Despite the drawbacks, the language became a tool for research visualisation. Researchers could concentrate on data structuring and analysis and leave the rendering issues to browsers offered freely on Internet. The major 3D progress is observed in the area of data presentation. All traditional GIS vendors provide extended tools for 3D navigation, animation and exploration. However, many of these systems still are lacking full 3D geometry. In this order of thoughts, the understanding for GIS is changing.

Instead of a monolith, desktop, individual system, GIS is becoming an integration of strong database management ensuring data consistency and user control and powerful editing and visualisation environments inheriting advanced computer graphics achievements. At present, only the first step is made, i. The third dimension with respect to topological issues is still in the hands of the researchers. The case studies clearly showed the benefits of a standardised spatial data structuring as well as revealed the very early stage of the integration.

The large number of specialised settings, the application dependent feature-geometry linkage, the limited semantic hierarchy, the spatial operators utilising only X, Y values, are some of the issues that need further improvement. Although, there are quite a significant number of works devoted to 3D data structuring, the research is concentrated around a few basic ideas, as the level of explicitly described spatial relationships varies.

Each suggested data structure exhibits efficiency and deficiency with respect to particular applications and operations to be performed. Still 3D GIS functionality needs to be addressed: 3D buffering, 3D shortest route, 3D inter-visibilities are some of the most appealing for research. Integration of object-oriented approaches with the 3D GIS raises research topics at a database level toward standard object descriptors and operations.