What technique did Sean Reid use in Sierra Leone to refine satellite imagery of his research area? Select one: 1. Electromagnetism 2. Ground truthing 3. Pan-sharpening 4. Multi-spectral imagery

The technique that Sean Reid used in Sierra Leone to refine satellite imagery of his research area is: **2. Ground truthing**. Ground truthing involves collecting actual data on the ground to validate and enhance the accuracy of satellite imagery and remote sensing data.