Airborne Remote Sensing
A NEON Airborne Observation Platform (AOP) is an array of instruments installed into a light aircraft to collect high resolution remote sensing data at low altitude. Airborne remote sensing surveys are conducted over NEON field sites during peak greenness to collect quantitative information of each field site on land cover and changes to ecological structure and chemistry, including the presence and effects of invasive species across landscapes.
Spatial and Temporal Design
Three payloads of AOP sensors are calibrated and validated each spring at the AOP lab in Boulder, CO. The AOPs are then installed into twin otter aircrafts and prepped for the flight season which typically runs from May - October.
When conducting a survey of land, the aircraft is flown at an average of 1,000 meters Above Ground Level (AGL) flying altitude providing seamless hyperspectral and gridded LiDAR remote sensing data products at approximately one-meter spatial resolution, and digital photography at approximately 0.25 meter resolution. The data collected by the AOP are processed by the NEON project and then published to the NEON data portal. Each year, NEON surveys 75% of field sites on a rotating basis. The flight box for each field site ranges from 100-300km2.
Data collection is synchronized with field sampling and automated instrument measurements collected on the ground at each site.
AOP Data Collection Capabilities
Data collection includes:
NEON operates two Optech ALTM Gemini systems and a Riegl LMS-Q780 to collect both discrete and waveform LiDAR data.
Resolution: Discrete point cloud data and waveform data: approximately 1-4 points/waveforms per square meter. Discrete-derived surface topography products: Approximately one meter at 1000 meters above ground level (AGL) .
Data products include:
- Discrete return Lidar point cloud
- Lidar slant range waveform
- Slope and Aspect - Lidar
- Elevation - Lidar
- Ecosystem structure
NEON’s imaging spectrometer is a pushbroom collection style instrument (AVIRIS next-gen) that was designed and built by NASA’s Jet Propulsion Laboratory. It measures reflected light energy in greater than 420 narrow spectral bands extending from 380 to 2500 nm with a spectral sampling of five nm.
Resolution: Approximately one meter, at 1000 meters above ground level (AGL)
Data products include:
- Hyperspectral Flightlines and Mosaics
- Spectrometer orthorectified surface directional reflectance
- Spectrometer orthorectified at-sensor radiance (flightline only)
- Total biomass map
- Vegetation indices
- Canopy water content, lignin, nitrogen and xanthophyll cycle
NEON operates two Phase One iXU-RS1000 (100 MP) digital aerial cameras, and one Phase One iXA (80 MP) camera.
Resolution: 6.6 - 10.0 cm @ 1000m AGL
Data products include:
- High-resolution orthorectified RGB camera imagery and mosaics
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Why These Measurements?
NEON's open access AOP data fill a critical hole in ecological data collection. For example, standardized and routine airborne data collection over NEON field sites allows scientists to monitor changes in vegetation patterns and canopy chemistry on a continental scale over an extended time period. These data will provide new insights into how invasive species are spreading over time and how changes in climate and land use impact forest health and their ability to sequester carbon. These data may also be combined with field-based measurements to estimate ground and atmospheric conditions across sites. In situ and sensor data may be combined with AOP measurements to enable scientific study of continental-scale patterns and processes. Satellite data from other organizations may be used to fill in gaps between NEON sites or where NEON data do not exist to address ecological questions at regional and continental scales.
Vegetation health, distribution and biochemistry play an important role in how ecosystems change. Collecting airborne remote sensing data of an ecosystem can provide valuable insights into these processes, especially when they are surveyed following major disturbance events such as floods or wildfires. However, the equipment needed to collect these data can be cost prohibitive for a research study. In addition to routine surveys of NEON sites, NEON can also conduct AOP surveys for researchers to advance ecological research and environmental studies.
During a flight survey, the AOP is deployed and operated by a NEON airborne sensor team. The data collected by the AOP are processed by NEON and then delivered to the research team. NEON can also provide ground support (e.g., ASD field spectroradiometer to collect foliar spectral measurements) for flight survey as needed. As with NEON’s other Assignable Assets, the requesting research team is responsible for covering NEON’s costs associated with deploying an AOP.
Examples of Using NEON's Airborne Data
The data are already being used by scientists for many different projects. For example, a team led by Dr. Phil Townsend, an ecologist out of the University of Wisconsin, is using the data to build a spectral library of vegetation types that links physical and biochemical traits to spectral data. This will enable scientists to classify and map plant species using remote sensing data. At the Smithsonian Environmental Research Center (SERC), Dr. Jess Parker, a forest ecologist, plans to incorporate AOP data into his studies of tree growth and the exchange of carbon, radiation and moisture between forests and the atmosphere. In addition, there have been several educational projects using NEON data including a late-2017 project led by Ethan White.
The NEON remote sensing team is working closely with the science community to optimize data collection for the needs of researchers. Two NEON Technical Working Groups (TWGs) have been formed to guide further data collection efforts, one on airborne sampling design and one on LiDAR. These advisory groups, along with additional discussions with researchers using NEON remote sensing data, will help refine data collection protocols and guide future decisions for expanded data collection or new instrumentation.
NEON has also conducted several airborne remote sensing surveys for researchers including a survey of Crested Butte, Colorado and continues to field requests each year.