SNAP Installation Guide for Sentinel-2 Water Quality Processing

What is SNAP?

SNAP (Sentinel Application Platform) is ESA’s official toolbox for processing Sentinel satellite data. It’s required for:

  • Atmospheric correction (C2RCC)

  • Geometric correction

  • Radiometric calibration

  • Band math operations

Installation Steps

1. Download SNAP

  1. Visit: https://step.esa.int/main/download/snap-download/

  2. Click “Download SNAP 10.0” (or latest version)

  3. Choose your operating system (Windows/Linux/Mac)

  4. Download the installer (approximately 1.5 GB)

2. Install SNAP

  1. Run the installer as Administrator

  2. Accept the license agreement

  3. Choose installation directory (default is fine: C:\Program Files\snap)

  4. Select components to install:

    • ✅ SNAP Desktop

    • ✅ Sentinel-1 Toolbox

    • ✅ Sentinel-2 Toolbox

    • ✅ Sentinel-3 Toolbox

    • ✅ SNAP GPT (Graph Processing Tool) - REQUIRED

  5. Install (this may take 15-30 minutes)

3. Verify Installation

Open Command Prompt and test:

# Test GPT command
gpt --help

# If you see help text, SNAP is working!

4. Add SNAP to PATH (if needed)

If gpt --help doesn’t work, add SNAP to your system PATH:

Windows:

  1. Open System Properties:

    • Right-click “This PC” → Properties

    • Click “Advanced system settings”

    • Click “Environment Variables”

  2. Edit PATH:

    • In “System variables”, find “Path”

    • Click “Edit”

    • Click “New”

    • Add: C:\Program Files\snap\bin

    • Click “OK” on all windows

  3. Restart Command Prompt and test: gpt --help

5. Configure SNAP (Optional)

For better performance, you can increase SNAP’s memory allocation:

  1. Find SNAP configuration:

    • Windows: C:\Program Files\snap\bin\gpt.vmoptions

  2. Edit the file (as Administrator):

    -Xmx8G
-Xms1G
-XX:+UseG1GC

    (Adjust -Xmx8G to your available RAM, e.g., -Xmx4G for 4GB)

Troubleshooting

Common Issues

  1. “gpt is not recognized”

    • SNAP is not in PATH

    • Solution: Add C:\Program Files\snap\bin to PATH

  2. “Java heap space” errors

    • Insufficient memory allocated

    • Solution: Increase -Xmx value in gpt.vmoptions

  3. Installation fails

    • Run installer as Administrator

    • Temporarily disable antivirus

    • Ensure sufficient disk space (>5GB)

  4. SNAP Desktop won’t start

    • Check Java version (SNAP requires Java 8+)

    • Update graphics drivers

Testing SNAP Installation

Run these commands to verify SNAP is working:

# Basic help
gpt --help

# List available operators
gpt -h

# Test C2RCC operator (required for water quality)
gpt c2rcc.msi -h

Integration with Water Quality Workflow

Once SNAP is installed, your workflow will use these SNAP operators:

  1. Read - Load Sentinel-2 data

  2. Resample - Resample bands to 10m

  3. Subset - Extract study area

  4. Reproject - Convert to WGS84

  5. C2RCC - Atmospheric correction for water

  6. BandMaths - Calculate CDOM

  7. Write - Save results

Performance Tips

  1. Increase Java heap size: -Xmx8G or higher

  2. Use SSD storage for faster I/O

  3. Close other applications during processing

  4. Process smaller areas if memory is limited

Alternative: Docker Installation

If you have issues with the regular installation, you can use SNAP in Docker:

# Pull SNAP Docker image
docker pull mundialis/esa-snap:latest

# Run SNAP GPT
docker run -v /path/to/data:/data mundialis/esa-snap gpt --help

Getting Help

  • SNAP Forum: https://forum.step.esa.int/

  • SNAP Documentation: https://step.esa.int/main/doc/

  • Tutorials: https://step.esa.int/main/doc/tutorials/

Quick Start After Installation

  1. Verify installation: gpt --help

  2. Run system validation: python validate_system.py

  3. Update credentials: Edit 02_config/parameters.yaml

  4. Run workflow: run_workflow.bat

System Requirements

  • OS: Windows 10/11, Linux, macOS

  • RAM: 8GB minimum, 16GB recommended

  • Disk: 10GB for installation, 50GB+ for processing

  • Java: Version 8 or higher (usually included with SNAP)

Remember: SNAP installation is a one-time setup. Once installed and configured, your water quality processing workflow will run automatically!