Compositing of these water detections, over 1, 2, and 3 days, to minimize false positives and fill in observations as clouds move.

Water detection algorithm applied to MODIS observations (Terra and Aqua).

Product generation consists of three key steps: Currently, only the 2- and 3-day products are viewable in Worldview. If clouds are not present, or latency is a primary concern, the 1-day product may be appropriate.

It is recommended that the user review both the 2- and 3-day products to determine which provides better coverage for a given event. The product is generated with three compositing periods (1-day, 2-day, and 3-day) because the best product for a given flood event depends on unpredictable factors: the specific area of interest cloud cover over dates of interest potential spatial extent of likely flood water and likely duration of flooding. We employ a multi-observation compositing approach to minimize these errors, generally requiring more than one water observation to mark a product pixel as water (flood or surface water). Although water detection at this scale is relatively straightforward with MODIS’s red and near-infrared bands, cloud and terrain shadows can create false-positives. The Flood Product is a daily, near-global, ~250 m resolution product showing flood and surface water detected from the twice-daily overpass of the MODIS optical sensors (onboard Terra and Aqua satellites). It replaces the previous legacy NASA NRT Global Flood Mapping Product, which was generated from 2011 to 2022 (see below).

The MODIS Near Real-Time Global Flood Product (Collection 61) (BETA) (MCDWD) is processed by NASA's Land, Atmosphere Near real-time Capability for EOS ( LANCE).

Shadows at the water's edge download