Vaguely speaking, irradiance is the amount of light incoming to a certain point from possibly all directions, while radiance is the amount of light incoming to a point from a single direction.

### What is difference between reflectance and radiance?

What is the difference between radiance and reflectance? Radiance is the variable directly measured by remote sensing instruments. Reflectance is the ratio of the amount of light leaving a target to the amount of light striking the target. It has no units.

As shown in Figure 1, the radiance (R) of the source emitting area (A) equals the radiation power (P), which is emitted from A and propagates in solid angle Ω, divided by the area A and the solid angle Ω: R = P / (A x Ω).

Irradiance Measurements In contrast to radiance measurements, irradiance is the radiant flux received by a surface or the flux that is incident on the surface. The irradiance unit is determined as power per unit area.

## What is irradiance computer vision?

Irradiance: power per unit area falling on a surface. dΦ

### Is irradiance the same as intensity?

According to SI standards, the power per unit area is called the irradiance and intensity is a different quantity. However, colloquially, intensity and absolute intensity is also used for irradiance. StellarNet uses the two words interchangeably to mean power per unit area.

Irradiance: Rrs is the ratio between water-leaving radiance (Lw, above the sea surface) and downwelling irradiance (Ed, above the sea surface). Lw can be estimated from above-water radiometric measurements, in this case reflected skylight must be removed using a “surface reflectance factor” (rho).