Visualization Principles in 3D Cadastre: A First Assessment of Visual Variables

This paper proposes to investigate which among visual variables are more appropriate (if they are) for geo-visualization of 3D legal units in a probable 3D cadastre system. Visual variables, as proposed by Bertin (1983), include position, size, shape, value, color, orientation and texture. The appropriateness is evaluated base on whether a visual variable can be selective or not in the context of visualising 3D cadastral features. From a literature review, five requirements are identified and used to carry out the assessment. Namely they are represent bounded and partial bounded 3D legal units, represent the relationship between 3D legal units and 2D land parcels, represent the relationship of 3D legal units with corresponding physical object, represent spatial relationships among 3D legal units and label with official measurements. The results clearly show that changing the position of the visual variable for selectivity purpose is not an adequate strategy, except to distinguish bounded and unbounded 3D legal units. A change in size of point and line or in color is fully suitable no matter is the requirement. If there is light source and shading effect in 3D cadastre visualization, value is not a promising choice. However, in a self-illuminating situation, in which there is no light source and shading effect, value could be used to represent all situations. Labeling with official measurements is the requirement the least fulfil