# 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
Sensor Irradiance sensorirradiance W/m² lux W/m3
Scene Radiance sceneradiance W·sr/m² cd/m² W·sr/m3
Scene Irradiance sceneirradiance W/m² lux W/m3
Sensor Power sensorpower W lm W/m
Sensor Exposure sensorexposure J/m² lux·s J/m3