Boundary labeling: models and efficient algorithms for rectangular maps

In this paper, we present boundary labelling, a new approachfor labelling point sets with large labels. We first place disjoint labels around an axis-parallel rectangle that contains the point sites. Then, we connect each label to its site such that no two connections, so-called leaders, intersect. Such an approach is common e.g. in technical drawings and medical atlases, but so far the problem has not been studied in the literature. The new problem is interesting in that it is a mixture of a label-placement and a graph-drawing problem. We consider attaching labels to one, two or all four sides of the rectangle. We investigate rectilinear and straight-line leaders. We present simple and efficient algorithms that minimize the total length of the leaders or, in the case of rectilinear leaders, the total number of bends.