Circular interfaces such as those found on smartwatches, automotive dashboards, cockpit instruments, or in radial visualizations pose unique challenges for placing readable labels. Traditional rectangular labeling methods waste screen space and create visual clutter on these constrained displays. In orbital boundary labeling, the labels (e.g., the features' names) are placed in an annulus-shaped orbit outside of the figure, and each label is connected to its feature using a short, crossing-free leader line. We contribute algorithms to compute two leader styles, orbital-radial and straight-line, for uniform and non-uniform label sizes, optimizing for crossing-free shortest leaders. We evaluate the model and the algorithms with computational experiments and a controlled user experiment. The user experiment reveals that both leader types exhibit similar accuracy, but straight-line leaders yield faster response times.

翻译：智能手表、汽车仪表盘、驾驶舱仪表或径向可视化等圆形界面为可读标签的放置带来了独特挑战。传统的矩形标注方法在这些受限显示屏上既浪费屏幕空间又造成视觉混乱。在轨道边界标注中，标签（例如特征名称）被放置于图形外部的环形轨道上，每个标签通过一条短小且无交叉的引导线与其对应特征相连。我们提出了计算两种引导线样式（轨道径向式与直线式）的算法，适用于均匀与非均匀标签尺寸，并以无交叉最短引导线为优化目标。通过计算实验和受控用户实验对模型与算法进行评估。用户实验表明两种引导线类型在准确性上表现相近，但直线式引导线能带来更快的响应时间。