## 1 Introduction
### Spatial Analysis of User Navigation and Interaction  
In recent years, progress in the field of geo-visualization has brought about studies on user strategies that make use of cartographic visualizations. For example, [PERSON] et al. [27] explored the usability of web mapping navigation in different interfaces. Using the combined metrics from a computer mouse and eye-tracking, they found significant differences between different types of interface and spoke in favor of the standard GIS approach of rectangle zoom, followed closely by wheel zoom. [PERSON] and [PERSON] [28] employed a similar approach to evaluate the effect of time constraints on the usability of a 3D geo-visualization (Google Earth displayed on a computer screen and controlled with a computer mouse). Participants dealt with practical tasks such as assessing the elevation of given points. The proportionality of applied movement interaction types was monitored--this constituted panning (the most common in both experimental conditions), zooming, tilting, and rotating. Interaction with geo-visualizations can also be analyzed in more detail; [PERSON] et al. [29] compared different pan and zoom function settings. Individual types of virtual movement can also be compared in control devices other than conventional computer mice, i.e., a touch screen was used by [PERSON] and [PERSON] [30] and a Wii remote controller was used by [PERSON] et al. [14].  
The result of interaction with a VGE is usually movement within this environment, which is defined as navigational (or viewpoint) interactivity [31]. Movement of a viewpoint can be represented by a so-called travel path [32]. Analysis of user travel paths is a research method used primarily in studies of human-computer interaction (HCI) [33; 34] and 3D UIs [35]. [PERSON] et al. [36] used and analyzed travel paths to distinguish between two types of geo-visualizations (non-guided and guided) in the Google Earth software. [PERSON] and [PERSON] [20] and [PERSON] et al. [16] visualized user travel paths as trajectories when differentiating individual types of movement (zoom, pan, rotation) in a 3D geo-visualization. Additional visual or GIS-related analysis can be applied to user trajectories. [PERSON] et al. [34] and [PERSON] et al. [35] used visualizations of the paths of multiple users. [PERSON] and [PERSON] [33] and [PERSON] et al. [34] used heatmaps to depict presence density. As [PERSON] et al. [32] suggested, traveled distance and the amount of rotation or turns can be measured. When time (efficiency) and traveled distance is measured, the speed of a user's travel can be calculated [16; 20; 37].  
The use of VGEs lets us examine the influence of specific visualization UI settings on human interaction with the virtual world, especially considering user fluency/speed (efficiency) and correctness (effectiveness) in various perceptual and decision-making tasks. To better understand the whole process of interaction, user strategies must be analyzed while following defined goals. To precisely describe a user's strategy, we need to capture a wide range of behavioral information, such as user movement trajectory (distances or average speed) or control types used for navigation (e.g., pan, zoom or rotation of the viewpoint). Based on the principle of triangulation, which is conditioned by the controlled setting of a virtual environment, data collected in such VGEs are complex and can help reveal specific patterns in human behavior.