How users perceive transparency in the 3D visualization of cadastre: testing its usability in an online questionnaire

Using transparency as a visual variable in 3D geo-visualization offers several advantages since it can encode underlying data and at the same time relieve the occlusion. However, the usability of transparency has yet to be tested with intended users and it might vary from one application domain to another or from one task to another. This research project addresses the usability of transparency in 3D cadastre visualization, more specifically whether it helps users delimit property units (administrative boundaries) with their physical counterparts (e.g., walls) in condominium situation. In this situation, three types of boundaries (simple physical, simple administrative, and linked boundary, which is both physical and administrative) are involved in visualization, and three different transparency levels are used to represent these types. Empirical tests are administered in the form of an online questionnaire for university students in law (notarial law) and land surveying. The results show that, in general, using three different transparency levels is preferable and efficient solution to help users demarcate property units with their physical counterparts, and 63% participants correctly achieved their visual tasks with this design. Also, the transparency settings influence user’s performance. For example, applying very high transparency to simple administrative boundaries as compared to simple physical boundaries improves user certainty. Another important discovery is that many university students in notarial law are inexperienced with 3D visualization, and such inexperience affects the viewer’s certitude when carrying out visual tasks.