Labelplacement

Labelplacement refers to the process of assigning text labels to features in a visualization, map, diagram, or user interface in a way that preserves readability and avoids occlusion of important content. It encompasses static labeling, which is fixed to a design, as well as dynamic labeling that adapts during user interaction such as zooming and panning. The term is used across cartography, data visualization, graph drawing, and information design.

In cartography and geographic information systems, label placement aims to maximize legibility while preserving feature association and map aesthetics. Constraints include avoiding overlap with map features and other labels, maintaining consistent labeling of related features, and respecting scale-dependent rules. Techniques vary from fixed-position labeling, where labels attach near their features, to leader labeling, where a connector line links the label to the feature. Automation often incorporates priorities, feature importance, and placement rules to guide decisions.

In data visualization and point labeling, the problem is typically modeled as selecting an anchor position from a discrete set around each feature to minimize overlaps and maximize legibility. This problem is generally NP-hard, prompting the use of heuristics and optimization methods such as greedy algorithms, local search, simulated annealing, genetic algorithms, or exact methods for small instances. Conflict graphs are commonly used to detect potential overlaps and guide placement decisions.

Key challenges include label stability during interaction, clutter at high feature density, legibility at small sizes, and multi-scale labeling as users zoom. Variants address non-overlapping labeling, stacked labels, or dynamic labeling that adapts to zoom level and user tasks. Evaluation often considers overlap metrics, label density, occluded features, and user performance on targeted tasks.