On the selection of 2D objects using external labeling.

We present an external labeling laid over small and/or overlapping 2D objects as an efficient representation for their selection. The approximation of objects with points allows us to transform the labeling problem to graph layout problem, which we solve by means of force-based algorithm. The input parameters allow us to influence the resulting layout of label boxes (e.g. to adapt their distance for imprecise input devices). In a study with 15 participants two implementations of our algorithm were compared against labeling method, where all label boxes share the same offset from corresponding objects. The results of the study show that implementation using a special functionality (temporary freezing of the label box position recalculation) was 14% faster with a comparable accuracy. The subjective evaluation revealed that the implementation with temporary freezing is perceived as most comfortable, fastest and most accurate. The implementation without temporary freezing showed much higher error rate and cannot be recommended.