NISAR Provisional Geocoded Unwrapped Interferogram Product (Version 1)

The NASA-ISRO Synthetic Aperture Radar (NISAR) Geocode Unwrapped Interferogram (GUNW) product is a Level 2 product derived from the Range Doppler Wrapped Interferogram (RIFG) and Range Doppler Unwrapped Interferogram (RUNW) products by geocoding the unwrapped phase and associated data layers (i.e., coherence magnitude, ionospheric phase screen) on a geographical grid at 80 m posting. Geocoding is performed using the orbit of the reference Range Doppler Single Look Complex (RSLC) product and a Digital Elevation Model (DEM) to project the data onto a predefined Universal Transverse Mercator (UTM) or Polar stereographic projection system map grid.

The geocoding algorithm uses a bilinear interpolation for interpolating data layers with floating-point data types, Sinc for the complex wrapped interferogram, and nearest-neighbor interpolation for unsigned integer datasets (e.g., connected components mask). The GUNW products also include the wrapped complex interferogram (multilooked at 30 m in range-Doppler coordinates and geocoded at 20 m posting), the unwrapped interferometric phase in radians (80 m posting), the normalized interferometric coherence magnitude (20 m and 80 m posting), connected components mask, and sub-pixel offset layers obtained from incoherent cross-correlation.