Combining OPERA Dynamic Surface Water Extent (DSWx) with in situ measurements to improve product development and application

NASA created the Observational Products for End-Users from Remote Sensing Analysis (OPERA) project to develop satellite-based analysis ready data products for resource management, environmental protection, and science. The OPERA product that is focused on inland surface water detection, Dynamic Surface Water Extent (DSWx), will be produced using data from both optical and synthetic aperture RADAR systems. The first DSWx product release (DSWx-HLS) relies on Harmonized Landsat Sentinel-2 (HLS) data to yield a median observation frequency of 3 days at the equator with near-global coverage. Subsequent DSWx releases will be based on inputs from Sentinel-1, Surface Water Ocean Topography (SWOT), and NASA-ISRO Synthetic Aperture Radar (NISAR).

DSWx accuracy in monitoring open water bodies is estimated through comparison with coincident, higher spatial resolution satellite imagery for locations around the globe. DSWx product suite algorithms also target the detection of mixtures of water and vegetation at input data subpixel scale as well as water under vegetation. The accurate assessment of algorithm performance given these especially challenging targets requires the development and analysis of databases that have as a foundation, data collected in the field.

A DSWx predecessor (USGS DSWE) and provisional DSWx data have been combined with in situ data on river discharge, aquatic species occurrence, water quality, and wetland processes to test and develop product utility. At sites spread across the US, low-cost sensors have been employed to record surface inundation. Trail cameras adapted for scientific research are providing useful information on weather, vegetation, and water conditions. Imagery from multiple high-resolution remote sensing instruments, including uncrewed aerial systems and commercial satellites, as well as sensors on-board the International Space Station, are being periodically collected. During intensive field campaigns, vegetation structure is being measured at each site. The imagery and in situ data are combined to improve DSWx development, uncertainty assessment, and application.