Bertin - Special topic

Bertin’s Sémiologie Graphique @ 50 – I

6603.3 - The design of cartographic symbol system without dependency on GIS platform

Thursday, July 6
3:30 PM - 3:50 PM
Location: Virginia A

Symbols are the main forms to illustrate graphical elements in mapping. Thus, the design of symbol library directly affects the quality of digital map and geographic information acquisition efficiency using Geographical Information System (GIS) platform. Generally GIS software manages symbol library as different separate files. Consequently, there often exist various disparities between different GIS software, each of which possesses its own cartographic features and the corresponding symbols system. Therefore, it is commonly difficult to achieve cross-system symbol sharing for different GIS software.
We design a system to meet the commonality need for different users with different GIS software expertness. In this system, the cartographic symbol will have two distinctive properties, one is graphics and the other is attribute. Graphic property is the most direct and most fundamental aspect in any mapping visualization, whereas the attribute property assigns and controls the size, color, tissue or angle of the symbol to denote the scale and feature of specific geographic object or phenomenon. For different cartographic geographic objects that share a common property, they can serve as different symbols with modification of the attribute properties for the same graphics. One example is the contour symbol of snow mountains. The intermediate contour and index contour can be represented using blue solid lines with 0.01 mm and 0.02 mm thickness of the same solid line. This means the modification of thickness of contour could result in the modification of symbol representation.
The structure of this proposed cartographic symbol system will be organized in a spatial database manner. The information of any symbol, whether it be point, line or area will have two parts, its graphic appearance and its own attribute. In many cases, the attribute of symbol, rather than the entire symbol itself, will vary according to the corresponding geographical information it represent. The structure of this symbol database will be designed in the following way. First, all symbols will be categorized based on their own geometry type. Then for a certain symbol, the graphic information and attribute will be store separately. Furthermore, three index tables will be established, one for the graphic information, one for the attribute information, and one for the symbol information. In the last symbol index table, in addition to normal details it may encompass, an extra field named “SymbolCode (SC)” will be created so as to set up the linkage among all three index table. This SC would be designed as an eight digit CHAR type variable, in which the first four-digit would denote the ID number in graphic index table and the last four-digit represents the ID number in attribute index table. Thus, the SC variable will be deemed as a retrieval pointer in the other two tables, the graphics and the attribute, and after the successful retrieval, a complete symbol with specific denotation will be eventually constructed. Take the road design for example. There are national road, state/provincial road, city road, town road and county road. Traditionally, they are stored using different line symbols in different GIS platforms. Nonetheless, if we adopt the library system mentioned above, only one graphic information will be required to be stored. The variation of different line symbols can be signified using different attribute information. Moreover, would an extra road with specific function need to be created in the GIS platform, we only need to append a specific attribute in the attribute index table and update the symbol index table for the realization of the mapping visualization of this specific road.

Zhao Li

engieer
National Geomatics Center of China

LI Zhao(1988-), Female, Master of Science in Catography, Currently an Engineer in National Geomatics Center of China(NGCC).
In 2012, I graduated from China University of Geoscience in Beijing with a MS degree and since then have been working as an engineer in the database department in NGCC. My main responsibilities in NGCC include supervising, inspecting, coordinating provincial maps collected from different regions in China, and compiling them so as to update the National Geographic Map of scales of both 1:5000 and 1:20000 each year.
If you have any questions, please don't hesitate to contact me. I can be reached either by e-mail or telephone.
E-mail: lzh@nsdi.gov.cn
Tel: +86 10-63880332

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Alan M. MacEachren

Professor of Geography
Penn State University

Alan M. MacEachren is Professor of Geography, Affiliate Professor of Information Sciences & Technology, and Director of the GeoVISTA Center at the Pennsylvania State University. MacEachren’s research foci include: geovisual analytics, cartography, geovisualization, geographical information retrieval/geoparsing, visual semiotics, spatial cognition, human-centered systems, user-centered design, geocollaboration. He is author of How Maps Work: Representation, Visualization and Design and Some Truth with Maps, as well as co-editor of additional books and journal special issues. He chaired the ICA Commission on Visualization (1999-2005). MacEachren is an Honorary Fellow of the ICA (2005) and was elected as a Fellow of AAAS in 2014.

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