What do we use to acquire imagery?

• A. Ground surveys
• B. Satellites and airborne platforms (UAVs)
• C. Underwater sonar
• D. Radio tomography

Answer: (B)

Imagery is typically obtained from platforms carrying sensors high above the area of interest. Satellites in orbit and aircraft—including UAVs—carry cameras and other sensors to capture images of the Earth's surface in various wavelengths. This approach provides broad geographic coverage, the ability to revisit the same area over time, and a range of spatial resolutions to suit different analyses.

Ground surveys gather measurements directly from the ground, which is great for precise, localized data but not for producing wide-area imagery. Underwater sonar images submerged environments rather than the terrestrial surface. Radio tomography creates internal cross-sections from transmitted signals, which is a different imaging modality.