Analyzing the Sprawl of Built-up Areas Using Landsat Data and the Normalized Difference Built-up Index

The sprawl of built-up areas is one of the most important anthropic changes which lead to the development of cities. This study analyses the sprawl of built-up areas around the city of Brașov, Romania, on the basis of two Landsat satellite images acquired in 1985 and 2019. The analysis was based on satellite images obtained through the difference between the NDBI and NDVI indices calculated for each satellite image. The results show that in the period 1985–2019 built-up areas around Brașov and its surroundings increased considerably (24.6%). Furthermore, it was noted that, although the reflectance of built-up areas varies very little from one season to the next, it can be influenced indirectly by the presence in the studied area of agricultural land and barren land whose reflectance is seasonal. This phenomenon led to confusion among built-up, agricultural land and barren land in mapping built-up areas.