Date of Images:

8/10/2024, 8/22/2024

Date of Next Image:

None Expected

Summary:

The Alaska Satellite Facility has developed false color Red, Green, Blue (RGB) decomposition of the Sentinel-1A Synthetic Aperture Radar (SAR) instrument which assigns the co- and cross-polarization information to a channel in the composite. When used to support a flooding event, areas in blue denotes water present at the time of the satellite overpass. Blue areas have low returns in VV and VH (smooth surfaces such as calm water, but also frozen/crusted soil or dry sand), Green areas have high returns in VH (volume scatterers such as vegetation or some types of snow/ice), and Red areas have relatively high VV returns and relatively low VH returns (such as urban or sparsely vegetated areas).

Radiometric Terrain Corrected (RTC) products in VV and VH polarization generated from Sentinel-1 SAR imagery, processed by the Alaska Satellite Facility. Values for the VV and VH polarization are commonly driven by surface roughness and/or soil moisture, with rougher surfaces and higher soil moisture returning higher backscatter values. Surface water appears very dark under calm conditions, as the signal bounces off the surface away from the sensor. These products can be tougher to interpret in areas of complex terrain.

Additional SAR Information

Suggested Use:

It is recommended to use this product with ancillary information to derive flooded areas.

It is normal for the RGB to have holes in it in areas that were masked out due to shadow or certain terrain.

Satellite/Sensor:

Synthetic Aperture Radar on European Space Agency's (ESA) Copernicus Sentinel-1A satellite

Resolution:

30 meters

Credits:

Sentinel data used in this derived product, contains modified Copernicus Sentinel data (2023), processed by ESA, Alaska Satellite Facility, NASA MSFC

Esri REST Endpoint:

See URL section on right side of page

WMS Endpoint:

https://maps.disasters.nasa.gov/ags03/services/nepal_flood_202408/Copernicus_Sentinel_1A_for_the_Nepal_Flood_August_2024/MapServer/WMSServer

Data Download:

https://maps.disasters.nasa.gov/download/gis_products/event_specific/2024/nepal_flood_202408/Sentinel1_ASF/