topography

Topography is the study and depiction of the surface features of a region. It covers the shapes and elevations of the land and of human-made features, including mountains, valleys, plateaus, plains, coastlines, and settlements. The term emphasizes the land surface's relief and the spatial arrangement of its features at a given time.

Topographic information is produced by field surveys, remote sensing, and cartographic techniques. Elevation is measured relative to a reference surface, usually mean sea level. Common representations include topographic maps with contour lines or shaded relief and digital elevation models (DEMs) that store elevation data on a grid. Techniques such as LiDAR, radar, and photogrammetry yield high-resolution relief data; bathymetry describes underwater topography, while land topography concerns terrestrial surfaces.

Topography intersects with geomorphology, geodesy, and geographic information science. It influences hydrology, climate, ecology, and land-use planning, and it underpins engineering design and hazard assessment for floods, landslides, and other geophysical risks. The present landscape is the product of long-term processes—tectonics, volcanism, erosion, deposition, and glaciation—along with recent human modification.

Topographic data are used at regional and local scales for planning, routing, and environmental management, as well as in global relief studies and navigational systems. Data quality, resolution, and vertical accuracy affect modeling of terrain, watershed analysis, and viewshed calculations, and map products may use vertical exaggeration to emphasize relief in flat areas.