IEEE Std 4003:2021 pdf free download – IEEE Standard for SpaceborneGlobal Navigation Satellite System-Reflectometry (GNSS-R)Data and Metadata Content
nbrcs: This is an estimation of the normalized bistatic scattering radar cross-section (dB) derived fromdividing brcs by effective_area.For wind speed retrieval, a window of delay and Doppler bins centered inthe nominal specular point shall be used. This window shall correspond to a nominal spatial resolution on theEarth ‘s surface, e.g., ~25 km x 25 km for systems using the GPS C/A code[three delay and five Doppler bins inCYGNSS as shown in “Wind Speed Retrieval Algorithm for the Cyclone Global Navigation Satellite System(CYGNSS)Mission”].This window size shall be assumed to be a variable, and information shall be includedas metadata. Dimension category: matrix.
noise_floor: This is the noise floor of the complex (ddm_complex or ddm_complex_compressed) and power(ddm _power) DDMs. This information shall be included in the metadata. In the case of GNSS-R sensors ofthe c- and r-type, noise_floor shall include both direct and reflected correlation channels. The units of thenoise_floor shall be (dBm).The computation of noise_floor shall account for the type of surface i.e., oceanversus land, including the effect of topography discussed in“MERRByS Product Manual” and “”Analysis ofCYGNSS Data for Soil Moisture Retrieval.”It shall be computed for each individual DDM as the averageover the number of bins before the beginning of the leading edge,for all Doppler frequencies in the DDM.Dimension category: scalar.
snr: This is the signal-to-noise ratio(SNR) at each bin of the power DDMs outlined in “Sensitivity of GNSS-RSpaceborne Observations to Soil Moisture and Vegetation,”taking the level of noise floor as a reference, citheras a power spectral density in(dB·Hz^-l ) or as an integrated power in (dB), in which case the noise bandwidthshall be informed as metadata. In the case of GNSS-R sensors of the c- and r-type, snr shall include both directand reflected correlation channels. Several anomalies have been reported and analyzed in “Detecting Targetsabove the Earth ‘s Surface Using GNSS-R Delay Doppler Maps.””These anomalies are due to signals beingreflected from objects above the Earth ‘s surface, and they shall be considered when computing snr. Dimensioncategory: matrix.
gamma: This is an estimation of the physical reflectivity of the scattering surface. It shall be computed perbin of the calibrated power (ddm_power_cal) DDMs (dB), after compensation of the noise floor, and thedown-looking antenna gain as a function of the elevation angle. The overall path losses shall be corrected per“Sensitivity of CYGNSS Bistatic Reflectivity and SMAP Microwave Brightness Temperature to GeophysicalParameters over Land Surfaces.”The level of the reflected signal shall be dynamically calibrated with respectto the direct signal as described in“The PARIS Ocean Altimeter ln-Orbit Demonstrator”and “Tutorial onRemote Sensing Using GNSS Bistatic Radar of Opportunity.”The GNSS satellites antenna radiation patternin the direction of the up-looking antenna and the nominal specular point shall be assumed to be similar orestimated per“Tutorial on Remote Sensing Using GNSS Bistatic Radar of Opportunity” and Ruf [B17].Dimension category: matrix.
area and vol: This is the area (area) and the volume (vol) of calibrated power (ddm_ power_cal) DDMsdescribed in”Correction of the Sea State Impact in the L-Band Brightness Temperature by Means of Delay-Doppler Maps of Global Navigation Satellite Signals Reflected over the Sea Surface”and Valencia, et al.[B20]. In the case of GNSS-R sensors of the c- and r-type, area and vol shall include both direct and reflectedcorrelation channels. The volume and the area of the DDMs shall be evaluated in scatterometry applicationsover the ocean surface because they are related to the changes in the contribution to the brightness temperatureof the ocean induced by the surface roughness per”Correction of the Sea State Impact in the L-Band BrightnessTemperature by Means of Delay-Doppler Maps of Global Navigation Satellite Signals Reflected over the SeaSurface” and Valencia, et al. [B20].The shape of the calibrated power DDMs provides a measurement of thesize of the area (m ) over which the GNSS signals are scattered, which is also known as the glistening zone.Onthe other hand, vol (dB-m2) is the volume under the calibrated power DDMs, which increases with increasingroughness, since the region from which the signals are scattered enlarges. Dimension category: scalar.