The 3rd ISPRS Workshop on Dynamic and Multi-Dimensional GIS & the 10th Annual Conference of CPGIS on Geoinformatics

Chen, Jun

Bibliographic data

Monograph

Persistent identifier:: 856566209

Author:: Chen, Jun

Title:: The 3rd ISPRS Workshop on Dynamic and Multi-Dimensional GIS & the 10th Annual Conference of CPGIS on Geoinformatics

Sub title:: May 23 - 25, 2001, Bangkok, Thailand

Scope:: VI, 434 Seiten

Year of publication:: 2001

Place of publication:: Pathumthani, Thailand

Publisher of the original:: AIT

Identifier (digital):: 856566209

Illustration:: Illustrationen, Diagramme, Karten

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Monograph

Collection:: Earth sciences

Chapter

Title:: GENERALIZATION FOR 3D GIS. Fengwen BAI, Xiaoyong CHEN

Document type:: Monograph

Structure type:: Chapter

ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001 ed thousands of years zation of the reality is digital map/GIS is still our goal, namely the I research for 3D GIS examples: a) Levels of one, b) Symbolization ition and simplification provide an explorative i operators have been ess (Robert, W 1999). il means, is extremely aphers draw a reduced tant features, simplify features, and resolve , no doubt, operator- » are constantly built, ilization capability for field of generalization iplications. Noticeable marchers and some I digital generalization lowever, none of the provided a set of tools n needs. Aspects as an problems. I by both the existing . The future availability lowed us to realize our GIS, will be the basic are two niches in the is of generalization in i these theories have id 2D GIS. Automation digital map and 2D GIS isic theories even there ;o be found. 3D GIS as puter development will the basic theories with would be very valuable or 2D GIS but also for oduct. How to rule a 3D jr its data, detail and 3, for instance, can be only the walls and the ndows, doors, even the better to the user and The research can be a reference as a standard to the 3D GIS products designing and accepting according to the purpose. METHODOLOGIES Methodologies of generalization for 3D GIS are studied from four aspects in this paper. 1. Levels of Systems In traditional 2D maps, also digital map/GIS, we use scales to level the different levels of systems. We normalize the features (size, symbol, etc.) for each scale. 3D GIS, however, has the different characteristics with 2D map/GIS. In the first level there are four levels normally have effects on the single steps of the project realization and have to be heeded from the data capture to the modeling up to the visualization of the feature. The four levels are distinguished as global, area, town, feature. • Global The lowest step of the detail classes is used to display the large distribution from a large area to the whole world. In this case, all the elements such as cities are show as a symbol (symbolization of the features). Normally, the function of this level is used to give the index to the system. The feature is almost scaled down less than 1:100,000 and the elements of the system are made up mainly of cities and roads and other thematic features. • Area The second level is often to describe an area including one or several first or second district of a country. At this level, a few thematic elements are emphasized and the features in the cities are more generalized to leave the main streets, main buildings and thematic features. The features are scaled from 1:100,000 to 1:25.000. • Town The more frequent useful level is used in the scale among 1:10,000 to 1:1,000. The level system is more detail to show the basic elements in a city, especially the buildings. Some basic characteristics are necessary such as geometrical shapes were added to the buildings that were reconstructed from ground plan and building height. In addition to this it is possible to cover the single facades with a texture. An additional presentation of streets facilities and objects of the greens are possible. According to the scale and the size of the features (buildings), three sublevels are used to display them. Block Model (BM): Presentation of the buildings as block with or without shape of roofs, texture, spacing between buildings and functions, mainly street texturing and greens. The scale is about from 1:10,000 to 1:5,000. Mixed Block Model (MBM): The middle sublevel presents different buildings using the four kinds of symbols. Some of the main buildings are separated alone from the block. The scale is from 1:5,000 to 1:2,000. • Feature In this most detail class the area is defined in special rang such as a park, a temple or a round of buildings and the buildings are generated with a high level of realism. Additionally, in comparison with Town level, more detailed street objects (e.g. traffic-lights) and a more detail objects of the greens (e.g. detail vegetation objects) are presented. These objects are supplied with a photo-texture. Due to large data quantities only a project related visualization of small areas in this detail class is realized. The scale area for these models lays between the 1:500 and 1:50. Besides the defined levels above, a mixture of those is possible, depending on the description of the task. Within a certain frame, a flexible design of the respective detail class is possible. 2. Symbolization Symbolization is concerned with choosing the symbols, line weights, marks, colors, etc. used to present feature information. This component relates directly to aspects of production, and focuses on the manifestation of the graphic representation. GIS itself is a collection of symbols to display the multi dimension world. There are some kinds of conditions we use symbol to show the feature, such as: • The feature is so small that be displayed as symbol. • The feature is too small to be displayed as real dimension but it is very important for the purpose of the GIS, we use a symbol to show it in the GIS. • We want to emphasis or display feature such as gas station in the transportation GIS, but unnecessary to separate the building to around environment, for example, we do not need separate a restaurant from a round of buildings. There are 3+1 kinds of symbols using in GIS: • Pictographic symbol describes the enlarged outside volume model of the object and encoding on geographic and space phenomena. • Abstract symbol is the sketch chosen have a “natural"(or at least readily learned) relation to the objects and categories being symbolized. • Authentic symbol is the conceptual constrains symbol that operate directly upon the graphic depiction to maintain a natural semiotic relation between the manifest symbol and the visual expectations of the GIS user. • Collecting symbol is the collection of abstract symbol and authentic symbol, and that shows the special object. 3. Refinement Detail Block Model (DBM): The features are • Selection and Elimination presented as alone as they are according to the Selecting certain features or its elements into the final 3D GIS. applied purpose of the GIS. The main buildings What to be selected depends on the target scale and purpose, (presenting as Pictographic symbol) contain additional for instance, visual clarity. The selected features will presentation of building facades and further single participate further generalization operations. In the phase, we objects. The facilities of the street are displayed normally identify which feature will be selected and which class completely. of one |q nc j Q f feature will be selected roughly. In another hand, selectively eliminating features that are insignificant or

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