50 Years of Urbanization in South Korea

About This Chart

Data Visualization Method

• Data: A custom urban-intensity index reconstructed from two GHSL R2023A grids, resident population and built-up surface. The index is derived by the author and is not an official GHSL variable.
• Period and area: 1975–2025 at five-year intervals (11 time steps), covering land within South Korea's 17 current provincial-level regions, including Jeju and Ulleungdo. North Korea and the sea are excluded, and Dokdo is not part of the final grid.
• Index: For each 1 km cell, built-up share and population density are log-scaled and combined on a 0–1 scale. Built-up surface forms the base signal and population density adjusts it. The same formula and constants apply to every year, with no year-by-year rescaling.
• Selection: Cells above a low activity threshold in at least one year were kept, and very small isolated clusters were removed unless their signal was strong. The resulting 1 km locations were aggregated into 2 km cells, and 10,300 cells with the strongest signal across the full period were selected for display. Every year shows the same set of locations.
• Chart form: An animated point map with a play control and timeline. Each point is one selected 2 km cell at a fixed position; only its color and size change over time. Color runs from dark brown through amber to pale gold in seven classes. The classes reflect current intensity, with a limited lift for cells that grew faster than their current level alone would show.

Creator's Note

This map was built to compare fifty years of change in South Korea on one consistent scale. Population and built-up surface are combined into a single reconstructed index. The color and size hierarchy was balanced so the map would not simply show the capital region growing brighter, and so that growth, spread and relative stillness could be read across the whole country at once.

In the author's reading, several separate growth axes appear: the new towns around Seoul, the Sejong–Cheongju–Daejeon corridor, the Busan–Ulsan southeast coast, and the areas around Daegu and Gwangju. A supporting regional tally, not shown on the map, adds one contrast. Seoul ranks first in intensity per km² but last in composite growth since 1975, because it was already densely built by then. On a growth ranking, a place that filled up first can look like the one that stood still.

Data Sources

• GHS-POP R2023A — gridded resident population, 1 km, used for the population component of the index
• GHS-BUILT-S R2023A — gridded built-up surface, 1 km, used as the base signal of the index
• GHSL Data Package 2023 — reference for how both grids are produced and their known limitations
• Statistics Korea SGIS 2020 boundaries, via a StatGarten GeoJSON release — used only to assign cells to regions
• OpenMapTiles and OpenStreetMap contributors — basemap

Limitations

GHSL values are model outputs, not direct counts. Population grids distribute census or administrative totals across cells using built-up information, and the five-year series relies on spatio-temporal modeling rather than an independent image for each year. Layers through 2020 are model-based historical estimates; the 2025 frame is a GHSL R2023A projection. Early years, especially 1975, and sparse rural or scattered settlements carry greater uncertainty.

The index has no physical unit. Log scaling and the 0–1 cap reduce the effect of extremes but also compress real differences in scale. Color classes follow the distribution of values across all years and are not linear, so a brighter class does not mean a proportionally higher value. Because of the growth lift, two points with the same color can combine current intensity and past growth differently.

Aggregation to 2 km smooths fine spatial detail, and only 10,300 of about 25,900 land cells at that scale are displayed. Current regional boundaries are applied to all years, and do not reflect historical administrative borders. Coastal cells are assigned to their majority region, and a small number of display points were moved onto the nearest land cell to avoid falling in the sea. GHSL assumes built-up surface does not decrease, so demolition and redevelopment are not fully reflected.

What This Chart Doesn't Show

The map does not show population counts, economic output, income or official urban classifications. Brighter points are not a measure of prosperity. Dark or empty areas are not necessarily uninhabited: they may fall below the activity threshold or outside the cells selected for display. The number of points is not a measure of urban area.

Regional rankings mentioned on this page come from a supporting tally of the 1 km data and are not displayed on the map. "Relative stagnation" there means the bottom five of a composite growth ranking among 17 regions, not decline. The 2025 frame uses the same styling as earlier years but remains a projection rather than an observation.