Measurement & Experimental Science
PPFD Mapping & Daily Light Integral
One light reading cannot describe a canopy. A spatial PPFD map and photoperiod together provide a better description of delivered photosynthetic light.
Key concepts
- PPFD is an instantaneous photon-flux-density measurement
- DLI integrates PPFD over time
- Canopy geometry creates high and low zones
- Sensor orientation and spectral response affect measurements
What to measure or observe
- Use a repeatable grid at canopy height
- Keep the sensor level and orientation consistent
- Record photoperiod
- Calculate mean, minimum, maximum, and spatial variation where useful
Common mistakes
- Taking only a center reading
- Comparing measurements made at different heights
- Ignoring photoperiod when discussing total daily light
- Treating one target as universal across all conditions
Visuals this lesson still needs
- PPFD measurement grid
- DLI calculation diagram
- Height comparison
- Uniformity heat map