UAV multispectral canopy imaging

Knowledge graph centered on UAV multispectral canopy imaging with 41 nodes and 140 connections. Top connected: Gothic, Crested Butte, Asteraceae, Artemisia tridentata, Populus tremuloides.

Method synopsis

Unmanned aerial vehicle flights with multispectral camera to capture georeferenced imagery of forest canopy in five spectral bands, with radiometric calibration using reference panel and downwelling light sensor.

Synthesized from method descriptions across 1 paper using this protocol.

Procedure as described in the canonical source

Steps below were extracted from the paper that introduces this protocol — Remote sensing of ploidy level in quaking aspen (<i>Populus tremuloides</i> Michx.) (2020), Journal of Ecology. Implementations in other papers (listed below) may differ.

1. Collect airborne canopy spectra
   In July 2017, we obtained multispectral images covering a total of four sites each of c. 500 m length. Sites were overflown by an UAS (Tarot, T560 Sport) flying a raster scan pattern at c. 90–120 m above ground level (i.e. 5–7 cm/pixel ground resolution or c. 5–6 cm² pixel treetop resolution). Flights occurred in late-morning conditions during fully sunlight or fully cloudy conditions (i.e. minimizing shadows from partly cloudy skies). Due to weather and permitting issues, flights were only carried out at the Burke or Jolanta-4 sites, nor at the very eastern edge of the Jolanta-3 site. Data were collected using a multispectral camera (Micasense, RedEdge) on gimbal mount. The camera obtained co-registered coverage of five spectral bands: blue (475 ± 20 nm), green (560 ± 20 nm), red (668 ± 21 nm), red edge (717 ± 10 nm) and near-infrared (840 ± 40 nm). Immediately prior to data collection, a calibration image was obtained of a ground-based grey reference panel (Micasense, Calibrated Reflectance Panel). UAS flight plans were implemented using Universal Ground Control Software (SPH Engineering), which automatically accounts for approximate elevation gradients within the flight area by maintaining the elevation above ground level via an integrated pressure sensor on the flight controller (Pixhawk). The flight missions specified 70%–80% front and side image overlap. Simultaneous to imaging, incident radiation was collected using a downwelling sensor at 1 s intervals. The multispectral images were stitched using Pix4D Mapper software. Pixel values were then converted to reflectance values based on calibration against the downwelling radiation and grey reference data.
   Quantities: 4 sites, c. 500 m length each, 90-120 m flight altitude, 5-7 cm/pixel resolution, 5 spectral bands, 70-80% image overlap, 1 s intervals for radiation sensorDuration: July 2017, late-morning flightsConditions: Fully sunlight or fully cloudy conditions to minimize shadows
   Equipment: Tarot T560 Sport UAS, Micasense RedEdge multispectral camera, gimbal mount, Micasense Calibrated Reflectance Panel, Universal Ground Control Software, Pixhawk flight controller, downwelling radiation sensor, Pix4D Mapper software

Typical Equipment

• Tarot T560 Sport UAS
• Micasense RedEdge multispectral camera
• Micasense Calibrated Reflectance Panel
• downwelling radiation sensor

Output Measurements

• multispectral canopy reflectance
• georeferenced imagery

Papers Using This Protocol (1)

Species Studied With This Protocol

Places Where Used