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Best practices for multispectral drone surveys

When executing multispectral (MSP) drone surveys using MicaSense sensors (e.g., RedEdge-MX, RedEdge-P, Altum-PT), DJI M3M, or Sentera and processing within the PIX4D app ecosystem (PIX4Dengine SDK, PIX4Dfields, or PIX4Dmapper), strict data acquisition standards must be met to ensure accurate radiometric calibration and successful photogrammetric alignment.

IN THIS ARTICLE

Flight planning and overlap
Altitude constraints
Radiometric calibration practices
Environmental conditions
Camera and sensor configuration

Flight planning and overlap

  • Flight plan: Ensure the imagery is captured at Nadir (pointing straight down).
  • Standard overlap rates: Set an absolute minimum of 75% frontal and 75% side overlap.
  • Flight boundary: Always plan the grid survey area to extend significantly larger than the actual Region of Interest (ROI) to prevent edge-artifact degradation during stitching.
  • Camera triggering (MicaSense specific): Configure the sensor to Overlap Mode via the MicaSense app rather than a strict timer. In Overlap Mode, the camera relies on the DLS2 GNSS sensor to automatically fire only when the distance traveled yields the target overlap.

Altitude constraints

  • Baseline altitude: Maintain a flight altitude at or above 40 meters (130 feet) AGL. Flying lower might cause matching failures over complex canopies.

Note: For more information: I need to fly at low altitudes, how can I improve the odds this data can be processed? 

Radiometric calibration practices

To generate true reflectance maps rather than arbitrary digital numbers, you must systematically capture environmental light data.

 Note: For more information: How to process MicaSense sensor data in PIX4D.

  • Calibrated Reflectance Panels (CRP): Capture a clean, unshaded image of your calibration panel at least 3 times immediately before and after the capture mission.
    • The panel must be placed perfectly flat on the ground.
    • The drone operator must step back to avoid casting shadows or standing close enough to reflect clothing color onto the panel.
    • The target should be aligned with the North to avoid artifacts when applying sun angle correction.
  • Sun sensor (DLS2): Ensure the drone-mounted Downwelling Light Sensor (DLS2) has an entirely unobstructed view of the sky. Do not position it beneath propellers, frame elements, wires, etc.

Environmental conditions

  • Illumination uniformity: Fly exclusively under consistent light conditions, either completely clear skies or uniform, heavy overcast.
  • Avoid rolling clouds: Do not capture data on partly cloudy days (scattered/broken cloud cover). Passing clouds cause rapid shifts in ambient irradiance, introducing severe striping and patching artifacts in the orthomosaics.
  • Solar window: Conduct flights within ± 2.5 hours of local solar noon to mitigate long shadows and minimize sun glint (hotspots) off vegetation.

 Note: For more information: How to capture drone images for optimal results in PIX4Dfields 

Camera and sensor configuration

  • Exposure settings: Leave the camera exposure on Auto Exposure. The combination of auto-exposure metadata and DLS2 tracking allows PIX4D algorithms to normalize illumination frame-by-frame during radiometric processing.
  • Resolution and aspect ratio: Capture at full resolution and do not modify the native aspect ratio in the sensor configuration.
  • Dewarping: Turn it OFF. If utilizing a host platform or app that applies on-board dewarping corrections, disable it completely. PIX4D algorithms require the native, raw, uncorrected image geometry to accurately align the separate bands.