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Built-up Growth in Bengaluru, 1965-2023

Built-up area in hectares for the years 1965, 1993, 2004, 2013 and 2023

Overview

Measuring how far Bengaluru's built-up land — buildings and roads — has spread over 58 years, starting from the oldest satellite imagery available for the city. The 1965 extent is digitised from declassified CORONA imagery in QGIS; the 1993, 2004, 2013 and 2023 extents are classified from Landsat and Sentinel imagery with a Random Forest classifier in Google Earth Engine. The built-up area for every year is then measured from the pixel counts in QGIS.

  • Study Area: Bengaluru, India
  • Period: 1965-2023
  • Projection: EPSG:32643 (UTM zone 43N)
  • Role: Solo project
  • Status: Completed

Methods & Tools

Data Sources

  • Declassified CORONA satellite imagery (1965)
  • Landsat and Sentinel imagery (1993, 2004, 2013, 2023)

Processing Steps

1965 — georeferencing and digitising in QGIS

  1. Georeferenced the CORONA imagery using control points taken from road intersections, buildings and lake boundaries, with nearest-neighbour resampling and a third-order polynomial transformation
  2. Clipped and merged the georeferenced scenes into a single raster
  3. Digitised the built-up extent from that raster, where built-up land and vegetation stand out as the darker tones in the panchromatic image

1993-2023 — supervised classification in Google Earth Engine

  1. Generated an image composite for each target year
  2. Collected ground control points for four classes: built-up, water, bare and vegetation
  3. Classified each composite with a Random Forest supervised classifier
  4. Downloaded the classified rasters and visualised them in QGIS

Area measurement in QGIS

  1. Ran a per-pixel report on each classified raster and converted the pixel count for the built-up class into hectares

Tools Used

Tool Purpose
QGIS Georeferencing and digitising the 1965 CORONA imagery, per-pixel area reports, map layout
Google Earth Engine Random Forest supervised classification of the Landsat and Sentinel imagery

Key Findings

Year Built-up area (ha) Change Average per year
1965 6,900 — —
1993 18,307 +11,407 +407 ha
2004 26,908 +8,601 +782 ha
2013 38,441 +11,533 +1,281 ha
2023 44,970 +6,529 +653 ha
  • Built-up land grew from 6,900 ha to 44,970 ha over the 58 years, an increase of 38,070 ha and roughly six and a half times the 1965 footprint
  • The fastest expansion falls in 2004-2013, averaging about 1,280 ha a year, more than three times the average rate across 1965-1993
  • In 1965 the built-up land sits in separate patches around the city centre; by 2023 it covers most of the study area, with only scattered unbuilt pockets left