# Quantities¶

Ocean can compute not only images, but also physical light quantities. Quantities can be retrieved with various tools such as :

A quantity corresponds to the way light is gathered before the spectrum is integrated by the sensor channel response functions. Each instrument type gives access to different quantities. A combination of a quantity and a sensor response function gives a physical value with a unit.

For instance, the “Scene irradiance” quantity combined with the ȳ(λ) response function gives illuminance in lux.

## List of available quantities¶

• Sensor Irradiance : The amount of light per unit area reaching the instrument’s internal sensor.

• Scene Radiance : The amount of light incoming from the scene

• Scene Irradiance : The amount of light per unit area reaching the scene surfaces

• Sensor Power : The light flux reaching the instrument’s internal sensor.

• Sensor Exposure : Same as sensor irradiance, but integrated over the simulation time

• Raw : Instrument native values gathered by the sensor.

## Unit table¶

The following table list the unit of the physical value corresponding to each possible quantity/sensor combination:

Name

XML

Energetic

Photometric

Spectral

sensorirradiance

W/m²

lux

W/m3

sceneradiance

W·sr-1·m-2

cd/m²

W·sr-1·m-3

sceneirradiance

W/m²

lux

W/m3

Sensor Power

sensorpower

W

lm

W/m

Sensor Exposure

sensorexposure

J/m²

lux·s

J/m3

BSDF

bsdf

sr-1

sr-1

sr-1