Spatial Changes in Land Use and Building Density of the Baga Toiruu Area, Ulaanbaatar city

Abstract

By examining the interrelationships among urban spatial structure, building density, height distribution, street networks, and green space organization, it is possible to evaluate balanced urban development. The Baga Toiruu area, the historic core of Ulaanbaatar, represents a zone of high spatial and cultural significance, concentrating administrative, educational, cultural, and commercial functions. Recent redevelopment has intensified building density and height, leading to the degradation of traditional urban morphology and a decline in green and open spaces. This study presents the first GIS-based application in Ulaanbaatar using a fishnet grid approach to quantify morphological change through three indices: the Building Coverage Index (BCI), Building Height Index (BHI), and Green Space Index (GI). The research analyzes changes across 243.3 ha of redevelopment land using orthophoto imagery, land-use data, and spatial datasets for the years 2010, 2015, 2020, and 2025. A total of 1,067 grids (50 × 50 m) were generated to assess spatial patterns and temporal trends. Results indicate that between 2010 and 2025, the proportion of areas classified as “very low” GI increased from 42% to 56%, while high and very high BCI categories rose from 5% to 9%. The average BHI increased from 3.34 to 3.56, demonstrating a clear inverse relationship among the indices. Increased building density and height correspond directly with reduced green space coverage, providing quantitative evidence of growing morphological imbalance. These findings highlight the need for planning strategies that preserve historical urban structure, regulate building density and height, and ensure the long-term sustainability of green spaces in central Ulaanbaatar.