In planning a thermal solar inspection with a drone, which value is used to characterize solar irradiance on the surface?

• A. 30% load
• B. Radiance
• C. 600 W/m^2
• D. 5x5 grid for a 6in cell

Answer: (C)

The main idea is to quantify how much solar energy actually arrives per unit area on the surface. That quantity is irradiance, measured in watts per square meter (W/m^2). It directly represents the power the surface receives from the sun, which is what matters when planning a thermal inspection with a drone and interpreting the thermal camera data.

Radiance, while related to brightness, describes how bright a source appears per unit area per solid angle and isn’t the measure used for the total energy incident on a surface. The other two options don’t describe energy input: a percentage load is not an energy quantity, and a 5x5 grid refers to spatial sampling rather than the amount of sunlight hitting the surface.

Using a value like 600 W/m^2 provides a realistic, practical representation of surface irradiance for planning and calculations in thermal imaging under typical daylight conditions.