# External Labeling Techniques: A Taxonomy and Survey

## TL;DR

This paper provides a comprehensive taxonomy and survey of external labeling techniques used in visualizations, summarizing key algorithms, categorization, and open research challenges in this multidisciplinary field.

## Contribution

It introduces the first unified taxonomy for external labeling methods and offers a detailed survey of existing algorithms and research challenges.

## Key findings

- Developed a comprehensive taxonomy for external labeling techniques.
- Surveyed state-of-the-art algorithms and models in the field.
- Identified open research challenges and future directions.

## Abstract

External labeling is frequently used for annotating features in graphical displays and visualizations, such as technical illustrations, anatomical drawings, or maps, with textual information. Such a labeling connects features within an illustration by thin leader lines with their labels, which are placed in the empty space surrounding the image. Over the last twenty years, a large body of literature in diverse areas of computer science has been published that investigates many different aspects, models, and algorithms for automatically placing external labels for a given set of features. This state-of-the-art report introduces a first unified taxonomy for categorizing the different results in the literature and then presents a comprehensive survey of the state of the art, a sketch of the most relevant algorithmic techniques for external labeling algorithms, as well as a list of open research challenges in this multidisciplinary research field.