Abstract:

This file records the ground truth field data done for the National Center for Airborne Laser Mapping (NCALM). Airborne hyperspectral and Lidar data were collected in August 2015. Forty-three sites in east Barataria Bay, LA, were sampled on 16 – 22 August 2015. The sites were in freshwater, intermediate, brackish, and saline marshes, spanning habitats from < 5 psu (oligohaline) to 35 psu (polyhaline) and representing the entire coastal marsh ecosystem of Louisiana. The sites were sampled for spectral and biophysical (i.e. leaf area index (LAI), aboveground biomass, and canopy height) data.

Suggested Citation:

Riter, Joyce Christine. 2016. Ground truth field data for the NCALM airborne hyperspectral and Lidar data collected in August 2015. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7ZG6Q8G

Publications:

Mo, Y., Kearney, M. S., Riter, J. C. A., Zhao, F., & Tilley, D. R. (2018). Assessing biomass of diverse coastal marsh ecosystems using statistical and machine learning models. International Journal of Applied Earth Observation and Geoinformation, 68, 189–201. doi:10.1016/j.jag.2017.12.003

Purpose:

To provide ground truth for the NCALM airborne hyperspectral and Lidar data; and to develope empirical models to assess the marhes’ biomass with combined ground-, airborne-, and satellite-based passive optical remote sensing data.

Data Parameters and Units:

This file includes spectral data: surface reflectance; and biophysical data: leaf area index (LAI), aboveground green biomass (g/m2), aboveground brown biomass (g/m2), total aboveground biomass (g/m2), and canopy height(m).

Methods:

Forty-three sites in east Barataria Bay, LA, were sampled on 16 – 22 Aug 2015. Vegetation spectral and LAI data were collected from four subplots, canopy height was measured from three subplots, and aboveground biomass was collected from two subplots. All the subplots were randomly selected within each site. LAI was estimated using top-of-canopy digital color photography through the GreenCropTracker software that derives LAI from vertical gap fraction measurements (Liu and Pattey 2010, Liu et al. 2013). The digital images were taken by a camera (Canon PowerShot ELPH 110 HS) with 4.62 mm sensor horizontal size and 4 mm focal length looking down at the nadir angle. Aboveground biomass was collected from circular subplots had 20.32 cm (Site 1 – 16, 21, 22, and 25 – 43) or 56 cm (Site 17 – 20, 23, and 24) radius. All aboveground biomass within the subplots was gathered, put into labeled plastic bags, and then transported to the laboratory for further processing. Green and brown biomass samples was separated. A representative subsample (around 30 % by wet weight) of the each sample was dried at 80 °C for 24 – 36 hr until constant weight, weighed, and used to calculate the weight of the original sample. Aboveground green biomass, aboveground brown biomass, and aboveground total biomass were determined by dividing the dry weight of the corresponding samples by the area of the subplots (g/m2). Ground spectral measurements were taken by a FieldSpec 1 Spectroradiometer (ASD Inc. Boulder, CO, USA; Site 1 – 14, 17 – 20, 23, and 24) and a FieldSpec 4 Spectroradiometer (ASD Inc. Boulder, CO, USA; Site 15, 16, 21, 22, and 25 – 43) at 1.5 to 2 meter high. The FieldSpec 1 measures reflectance from 325 – 1075 nm and the FieldSpec 4 from 350 – 2500 nm. Processing by Yu Mo, J.C. Alexis Riter, and Michael S. Kearney of the Department of Environmental Science and Technology, University of Maryland, College Park, MD 20742.

Instruments:

LAI was estimated using a Canon PowerShot ELPH 110 HS digital camera. Ground spectral measurements were taken by a FieldSpec 1 Spectroradiometer (ASD Inc. Boulder, CO, USA; Site 1 – 14, 17 – 20, 23, and 24) and a FieldSpec 4 Spectroradiometer (ASD Inc. Boulder, CO, USA; Site 15, 16, 21, 22, and 25 – 43).

Provenance and Historical References:

Reference: Liu, J. G., and E. Pattey. 2010. Retrieval of leaf area index from top-of-canopy digital photography over agricultural crops. Agricultural and Forest Meteorology 150(11):1485-1490. doi: 10.1016/j.agrformet.2010.08.002 Liu, J. G., E. Pattey, and S. Admiral. 2013. Assessment of in situ crop LAI measurement using unidirectional view digital photography. Agricultural and Forest Meteorology. 169:25-34. doi: 10.1016/j.agrformet.2012.10.009

Individual Files: