Tonga Cyclone Damage Mapped by NASA's ARIA Team

The Advanced Rapid Imaging and Analysis (ARIA) team at NASA's Jet Propulsion Laboratory created this Damage Proxy Map (DPM) of Tongatapu, the main island of Tonga, following the landfall of Cyclone Gita, a Category 4 storm that hit Tonga on Feb. 12-13, 2018. The map depicts areas that are likely damaged from the storm, shown by red and yellow pixels. The map was produced by comparing two pairs of interferometric synthetic aperture radar (InSAR) images from the COSMO-SkyMed satellites, operated by the Italian Space Agency (ASI). The pre- and post-cyclone images were acquired on Jan. 19 and Feb. 13, 2018, respectively. The later image was acquired just 4-1/2 hours after the peak damage by the cyclone. The map covers the entire island of Tongatapu (the 25-by-25-mile, or 40-by-40 kilometer SAR image footprint indicated with the large red polygon). Each pixel measures about 98 feet (30 meters) across. The color variation from yellow to red indicates increasingly more significant ground surface change. Preliminary validation of the SAR data was done by comparing them with high-resolution optical imagery acquired by DigitalGlobe. This Damage Proxy Map should be used as guidance to identify damaged areas and may be less reliable over vegetated and flooded areas. https://photojournal.jpl.nasa.gov/catalog/PIA22257