To help increase understanding of synthetic aperture radar (SAR) and promote its use as a powerful tool for terrestrial ecologists, ASF offers examples of data that can be used for a variety of purposes. The data are subsets for selected field sites — such as flux tower locations — from the PALSAR (Phased Array L-band Synthetic Aperture Radar) sensor flown on the Advanced Land Observing Satellite (ALOS). This dataset provides SAR images for 42 selected sites from various terrestrial-ecology and meteorological-monitoring networks, including FLUXNET, AmeriFlux, Long Term Ecological Research (LTER), and the Greenland Climate Network (GC-Net).
Figure 1. SAR images for (a) Walker Branch Watershed, Tennessee, and (b) Niwot Ridge, Colorado, sites. In SAR visualizations for land use, green usually represents tree canopy, pink is crop or barren soil, black is water, and grays are low vegetation. The star icon indicates the location of the field site.
The data can be used for a number of purposes (1) to validate the SAR measurements using flux tower site characterization data; (2) to examine the impacts of vegetation dynamics on climate; (3) to understand human impacts on vegetation at a local scale; (3) to detect deforestation and forest degradation; (4) to map and differentiate growth stages and change; (5) to retrieve woody biomass and structural attributes; and (6) to characterize, map, and monitor ecoregions such as mangroves and wetlands.
More About Data Source
The SAR images are subset scenes of approximately 60 km x 70 km that include an established site in one of the monitoring networks. The spatial resolution of all scenes is 15 meters. These scenes are distributed as GeoTIFF files, with appropriate projection information defined within the file. The acquisition mode for all data is the Fine Beam Dual Polarization or FBD with the HH/HV polarization. The HH and HV channels are distributed as 3 channels to allow for an intuitive image display. The HH band is displayed in the red and blue channels, and the HV band is displayed in the green channel. The resulting images show vegetation in shades of green and barren land in shades of pink or purple. For some images only single polarization is available; these images are distributed as grayscale images.
The National Aeronautics and Space Administration (NASA) funded this EOSDIS Tech Infusion project as a collaboration between the ASF DAAC, the National Snow and Ice Data Center (NSIDC), and the Oak Ridge National Laboratory Distributed Active Archive Center (ORNL DAAC) in 2010.