https://tatcataittn.github.io/en/tags/sentinel-1/Sentinel-1HugoBlox Kit (https://hugoblox.com)en-usFri, 01 Dec 2023 00:00:00 +0000https://tatcataittn.github.io/media/icon.svghttps://tatcataittn.github.io/en/tags/sentinel-1/https://tatcataittn.github.io/en/blog/sar-deforestation/Fri, 01 Dec 2023 00:00:00 +0000https://tatcataittn.github.io/en/blog/sar-deforestation/<h2 id="what-is-sar-remote-sensing">What is SAR Remote Sensing?</h2> <p>SAR (Synthetic Aperture Radar) is a remote sensing technology that uses radar waves instead of visible light. Its biggest advantage: <strong>it works day and night, through clouds</strong>.</p> <p>This is particularly important in Vietnam — where cloud cover is nearly year-round, making optical imagery (Landsat, Sentinel-2) often unusable.</p> <h2 id="the-two-satellites-i-used">The Two Satellites I Used</h2> <h3 id="sentinel-1-esa">Sentinel-1 (ESA)</h3> <ul> <li>C-band (5.4 GHz)</li> <li>Revisit cycle: 6 days</li> <li>Free and open data</li> <li>Good for rapid change monitoring</li> </ul> <h3 id="alos-2-jaxa">ALOS-2 (JAXA)</h3> <ul> <li>L-band (1.2 GHz)</li> <li>Better canopy penetration → sensitive to forest structure</li> <li>Revisit cycle: 14 days</li> <li>Paid data (but available for research)</li> </ul> <h2 id="methodology">Methodology</h2> <ol> <li><strong>Data acquisition</strong> — download SAR images from Copernicus Hub (Sentinel-1) and JAXA (ALOS-2)</li> <li><strong>Preprocessing</strong> — radiometric calibration, speckle filtering, geocoding (using SNAP)</li> <li><strong>Change analysis</strong> — multi-temporal comparison, change index calculation</li> <li><strong>Classification</strong> — identify deforested areas using thresholds and dual-band combination</li> <li><strong>Validation</strong> — compare with ground truth and optical imagery</li> </ol> <h2 id="results">Results</h2> <p>Combining both satellites (C-band + L-band) yielded significantly better results than using either alone:</p> <ul> <li>L-band (ALOS-2) is sensitive to major structural changes in forests</li> <li>C-band (Sentinel-1) adds information about surface-level changes</li> </ul> <p>Results were published at the GIS-IDEAS 2023 conference.</p> <h2 id="tools-to-get-started">Tools to Get Started</h2> <p>If you want to start with SAR remote sensing:</p> <ul> <li><strong>SNAP</strong> (ESA) — free SAR image processing software</li> <li><strong>QGIS</strong> — open-source GIS</li> <li><strong>Python + snappy</strong> — processing automation</li> <li><strong>Google Earth Engine</strong> — cloud processing (free for research)</li> </ul>