Chapter 6 Visualization of Geospatial Data


6-1 Graphic Variables

Graphic representation of spatial data or maps, thematic data, tables and network with geographic reference and topology is very important to communicate geospatial data and the results of spatial analysis to all users.

Graphic representation in GIS will be implemented in the form of graphs, maps and images with XY plotters, dot printers, color monitors, color plotters etc. based on the knowledges of cartography, computer graphics, color theory, semiology and psychology.

Following graphic variables are used to display quantity, order, difference or similarity.

Location: geographic location and spatial relation of points, lines and areas are displayed in 2D space or map.

Size: Size of symbols and thickness of line represent quantitative difference. Physical difference does not coincide with psychological impression.

Density: density, intensity or gray scale is used to represent order and difference. Density or spacing of dot pattern or screen mesh should be carefully selected for the optimum gray scaling.

Texture: cyclic or repeated pattern of data, lines or symbols will represent difference as well as similarity.

Color: hue (H), intensity (I) and saturation (S) are aesthetically selected.

Orientation: directional pattern with hatching will represent difference as well as similarity.

Symbol: form of symbols will represent similarity of class or group.

Figure 6.1 shows the schematic concept of graphic representation.