UrbanizationAnalysis

Satellite-Based Urban Growth Analysis Using Sentinel-1/2 Data

📍 Multi-sensor satellite analysis using Sentinel-1/2 data to track Chennai urban expansion

🚀 Quick Start

1. Sign up for Google Earth Engine: earthengine.google.com
2. Open Code Editor: code.earthengine.google.com
3. Run Analysis: Copy any script from code/ paste, and Run!

⚡ No installation required! The entire analysis runs on the Google Earth Engine cloud infrastructure.

📊 Key Results

Chennai Metropolitan Area (1,200 km²)

Method	Growth (2018-2024)	Annual Rate
Optical (NDBI)	+7.43 km² (4.7%)	1.24 km²/year
Radar (SAR)	+88.15 km² (14.9%)	14.69 km²/year

• 🛰️ Sensors: Sentinel-1 SAR + Sentinel-2 Optical
• 🎯 Resolution: 10m spatial resolution
• 📈 Pop. Growth: ~91k new residents over 6 years

📈 Detailed Results

📊 Metric Breakdown

Metric	Optical (NDBI)	Radar (SAR)	Comparison
2018 Baseline	158.96 km²	592.43 km²	Radar covers 3.7x more
2024 Current	166.39 km²	680.58 km²	Radar covers 4.1x more
Absolute Growth	+7.43 km²	+88.15 km²	11.9x difference
Relative Growth	+4.7%	+14.9%	3.2x difference
Annual Rate	1.24 km²/year	14.69 km²/year	11.8x difference

🔍 Sensor Characteristics

• Optical (Sentinel-2): High precision for core impervious surfaces (buildings, roads). Clear spectral signatures but sensitive to cloud cover.
• Radar (Sentinel-1): Weather-independent. Detects surface roughness and structural complexity. Captures a broader range of infrastructure and mixed-use development.

🔬 Methodology

Our study employs a multi-sensor approach to overcome individual sensor limitations and provide a comprehensive map of urban density and structural change.

⚙️ Technical Specifications

1. Optical Analysis (NDBI) Uses the Short-Wave Infrared (SWIR) and Near-Infrared (NIR) bands.

• Formula: NDBI = (SWIR - NIR) / (SWIR + NIR)
• Threshold: NDBI > 0.1 classifies as Urban.

2. Radar Analysis (SAR) Analyzes VV polarization backscatter intensity.

• Source: C-band SAR (10m Resolution)
• Threshold: VV > -10 dB classifies as Urban.

🔧 Installation & Usage

1. Register: Apply for access at earthengine.google.com.
2. Clone: git clone https://github.com/arshsaxena/UrbanizationAnalysis.git
3. Execute:
   • Open the GEE Code Editor.
   • Paste the contents of combined_analysis.js.
   • Click Run to view the interactive map and console statistics.

📚 References

1. ESA: Sentinel-1 SAR User Guide
2. ESA: Sentinel-2 MSI User Handbook
3. Google: GEE Data Catalog
4. Census India: Population Statistics 2001/2011/2021