Light Sensors: the Basics (DLS and Sunshine Sensor)

The Downwelling Light Sensor for RedEdge (DLS)

The Downwelling Light Sensor (DLS) for RedEdge and the Sunshine Sensor for Sequoia are both irradiance/light sensors. When integrated correctly, they can help improve the radiometric quality of your data.

A light sensor measures irradiance, which is heavily dependant on the sensor’s orientation relative to the sun as it flies. For example, a light sensor pointing directly at the sun will measure a different value than one pointing straight up at the top of the sky. This is why it is important to have a correctly-calibrated magnetometer, which can provide heading and orientation information to help specialized processing software (like Atlas or Pix4D Mapper) make better decisions.

Light sensors are most effective at correcting for global changes in lighting conditions, such as when the sky is completely overcast and irradiance fluctuates during a flight. They cannot reliably correct for partly cloudy days where popcorn clouds may shadow part of the earth but not shadow the sensor.

For best results, you should follow the best practices for flying. For example, the best time to fly is around solar noon. This helps avoid shadows, which affect reflectance and prevent accurate analysis. The sensor should be mounted on a mast with a clear view of the sky, and completely unobstructed, so that no part of the aircraft can cast a shadow on the sensor itself.

In addition to the DLS or sunshine sensor, we strongly recommend that you continue to use a calibrated reflectance panel every time you collect data. The goal is to produce high quality, reflectance-compensated output. If captured correctly (as outlined in our best practices guide), calibrated panels provide the most reliable measurement of irradiance on the ground. They help confirm the information collected by the light sensor and serve to increase confidence in the overall result.

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