A GIS-based approach for assessing island landscape visual character: Reciprocal land–sea visual characterization in the Zhoushan Archipelago, China

Coastal tourism, port expansion, and land reclamation are intensifying pressures on island landscapes, highlighting the need for systematic visual assessment to support sustainable planning and management. To address this need, this study develops a GIS-based approach for the Zhoushan Archipelago that uses character mapping as the spatial organizing basis and examines reciprocal land–sea viewing conditions, from the sea toward land and from land toward the sea, across foreground and background zones. The approach comprises three stages: (1) mapping terrestrial, coastal, and marine landscape character types and areas; (2) calculating GIS-derived visual quality from viewing distance, visible range, horizontal angle, and vertical angle under land-based and sea-based foreground and background conditions; and (3) overlaying landscape character with visual-quality classes to compare spatial associations across viewing directions and distance zones. The results reveal different character–visual associations under reciprocal viewing conditions. For terrestrial landscapes viewed from the sea, high foreground visual quality occurred in both differentiated natural landforms and open, exposed waterfront configurations. Most terrestrial types shifted toward lower dominant classes in the background, while continuous, large-scale landform structures were more likely to retain relatively high visual quality. For marine landscapes viewed from land, high foreground visual quality was associated either with nearby coastlines and islands or with broad open-water configurations, and foreground–background changes were generally narrower. As a regional screening tool, the approach may provide a supplementary visual evidence layer for land–sea planning by identifying broad visual structures and relationships that warrant management attention or more detailed project-level assessment.