delineation

Delineation is the act of outlining or marking the boundary of a physical area or the precise definition of a concept. It involves identifying the limits that separate one feature from another and conveying those limits in a clear, usable form. The term comes from the Latin delineare, meaning to outline or sketch.

In cartography and GIS, delineation is the process of defining borders on a map, such as country boundaries, land parcels, or coastlines. It relies on legal documents, surveys, and natural features, and may be updated as boundaries change or as new data become available.

In urban planning and environmental management, delineation identifies zones, habitats, or land-use categories, helping authorities apply regulations and manage resources. In medicine, delineation (often called segmentation) marks the borders of anatomical structures or lesions in imaging studies, enabling measurement and analysis.

Techniques range from manual tracing by experts to semi-automatic and fully automatic methods using geographic information systems, image processing, or machine learning. Challenges include boundary ambiguity, resolution limits, cultural or legal disagreements about where a boundary lies, and variability between observers. Standardization and ground-truth data support reproducibility.

See also: boundary, segmentation, demarcation.