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Description

The SWOT Level 2 Nadir Altimeter Geophysical Data Record (GDR) with Waveforms dataset produced by the Surface Water and Ocean Topography (SWOT) mission provides sea surface height, significant wave height and wind speed measurements from the Poseidon-3C nadir altimeter, a Jason-class dual frequency (Ku/C) altimeter. SWOT is a joint mission between NASA and CNES that launched on December 16, 2022. It aims to measure ocean surface topography with unprecedented resolution and accuracy, as well as map inland water bodies globally. The GDR dataset consists of discrete measurements for each half orbit along the ground track with sampling resolutions of approximately 6-km and 300-m at 1Hz and 20Hz, respectively. The data were processed using restituted auxiliary data and the Precise Orbit Ephemeris (POE). The data are available with latency of < 90 days and distributed in netCDF-4 file format.

This collection is the parent collection to the following sub-collections:

https://podaac.jpl.nasa.gov/dataset/SWOT_L2_NALT_GDR_SSHA_D

https://podaac.jpl.nasa.gov/dataset/SWOT_L2_NALT_GDR_GDR_D

https://podaac.jpl.nasa.gov/dataset/SWOT_L2_NALT_GDR_SGDR_D

Product Summary

Platforms
SWOT
Instruments
Jason-class Altimeter ,
AMR
Spatial Extent

N: 77.6 S: -77.6 E: 180 W: -180

Location
GLOBAL
Coordinate System
CARTESIAN
Granule Spatial Representation
CARTESIAN
Temporal Extent
2022-12-16
Data Partner
Physical Oceanography Distributed Active Archive Center, Jet Propulsion Laboratory, NASA (NASA/JPL/PODAAC)
Concept ID
C3317113871-POCLOUD
Data State
ACTIVE
Number of Files/Granules
95682
Processing Level
2
Published
Updated
Science Keywords
Sea Surface Height ,
Significant Wave Height

Citation

Citation is critically important for dataset documentation and discovery. This dataset is openly shared, without restriction, in accordance with the EOSDIS Data Use and Citation Guidance.

Copy Citation

SWOT. (2025). SWOT Level 2 Nadir Altimeter Geophysical Data Record with Waveforms [Data set]. NASA Physical Oceanography Distributed Active Archive Center. https://doi.org/10.5067/SWOT-NALT-GDR-D Date Accessed: 2026-05-31

Documents

Variables

The table below lists the variables contained within a single granule for this dataset. Variables often contain observed or derived geophysical measurements collected from a variety of sources, including remote sensing instruments on satellite and airborne platforms, field campaigns, in situ measurements, and model outputs. The terms variable, parameter, scientific data set, layer, and band have been used across NASA’s Earth science disciplines; however, variable is the designated nomenclature in NASA’s Common Metadata Repository (CMR). Variable metadata attributes such as Name, Description, Units, Data Type, Fill Value, Valid Range, and Scale Factor allow users to efficiently process and analyze the data. The full range of attributes may not be applicable to all variables. Additional information on variable attributes is typically available in the data, user guide, and/or other product documentation.

For questions on a specific variable, please use the Earthdata Forum.

Name Description Units Data Type Fill Value Valid Range Scale Factor Offset
/data_01/ku/iono_cor_alt_filtered_mle3_qual filtered altimeter ionospheric correction quality flag (MLE3 retracking) N/A byte 127 N/A 1 N/A
/data_01/ku/iono_cor_alt_filtered_qual filtered altimeter ionospheric correction quality flag N/A byte 127 N/A 1 N/A
/data_01/ku/iono_cor_alt_mle3 An ionospheric correction must be added (negative value) to the instrument range to correct this range measurement for ionospheric range delays of the radar pulse. See SWOT Nadir Altimeter User Handbook m short 32767 N/A 0.0001 N/A
/data_01/ku/iono_cor_gim An ionospheric correction must be added (negative value) to the instrument range to correct this range measurement for ionospheric range delays of the radar pulse. See SWOT Nadir Altimeter User Handbook m short 32767 N/A 0.0001 N/A
/data_01/ku/off_nadir_angle_wf_ocean square of the off nadir angle computed from Ku band waveforms degrees^2 short 32767 N/A 0.0001 N/A
/data_01/ku/off_nadir_angle_wf_ocean_compression_qual quality flag for 1 Hz altimeter data: off nadir angle from Ku band N/A byte 127 N/A 1 N/A
/data_01/ku/off_nadir_angle_wf_ocean_numval number of valid points for square of the off nadir angle computed from Ku band waveforms count byte 127 0 to 20 1 N/A
/data_01/ku/off_nadir_angle_wf_ocean_rms Compression of high rate elements is preceded by a detection of outliers. Only valid high-rate values are used to compute this element degrees^2 short 32767 N/A 0.0001 N/A
/data_01/ku/range_adaptive All instrumental corrections included, i.e. distance antenna-COG (/data_01/range_cor_cog), USO drift correction (/data_01/range_cor_uso), internal path correction (range_cor_internal_path), Doppler correction (range_cor_doppler) and system bias m int 2147483647 N/A 0.0001 800000
/data_01/ku/range_adaptive_compression_qual quality flag for 1 Hz altimeter data: Ku band range (adaptive retracking) N/A byte 127 N/A 1 N/A
/data_01/ku/range_adaptive_numval number of valid points for Ku band range (adaptive retracking) count byte 127 0 to 20 1 N/A
/data_01/ku/range_adaptive_rms Compression of Ku band high rate elements is preceded by a detection of outliers. Only valid high-rate values are used to compute this element m short 32767 N/A 0.0001 N/A
/data_01/ku/range_cor_adaptive_net_instr Sum of distance antenna-COG (/data_01/range_cor_cog), USO drift correction (/data_01/range_cor_uso), internal path correction (range_cor_internal_path), Doppler correction (range_cor_doppler) and system bias m int 2147483647 N/A 0.0001 N/A
/data_01/ku/range_cor_ocean_mle3_net_instr Sum of distance antenna-COG (/data_01/range_cor_cog), USO drift correction (/data_01/range_cor_uso), internal path correction (range_cor_internal_path), Doppler correction (range_cor_doppler), modeled instrumental errors correction (range_cor_ocean_mle3_model_instr) and system bias m int 2147483647 N/A 0.0001 N/A
/data_01/ku/range_cor_ocean_net_instr Sum of distance antenna-COG (/data_01/range_cor_cog), USO drift correction (/data_01/range_cor_uso), internal path correction (range_cor_internal_path), Doppler correction (range_cor_doppler), modeled instrumental errors correction (range_cor_ocean_model_instr) and system bias m int 2147483647 N/A 0.0001 N/A
/data_01/ku/range_cor_ocean_net_instr_qual Threshold control of range_cor_ocean_net_instr N/A byte 127 N/A 1 N/A
/data_01/ku/range_ocean All instrumental corrections included, i.e. distance antenna-COG (/data_01/range_cor_cog), USO drift correction (/data_01/range_cor_uso), internal path correction (range_cor_internal_path), Doppler correction (range_cor_doppler), modeled instrumental errors correction (range_cor_ocean_model_instr) and system bias m int 2147483647 N/A 0.0001 800000
/data_01/ku/range_ocean_compression_qual quality flag for 1 Hz altimeter data: Ku band range N/A byte 127 N/A 1 N/A
/data_01/ku/range_ocean_mle3 All instrumental corrections included, i.e. distance antenna-COG (/data_01/range_cor_cog), USO drift correction (/data_01/range_cor_uso), internal path correction (range_cor_internal_path), Doppler correction (range_cor_doppler), modeled instrumental errors correction (range_cor_ocean_mle3_model_instr) and system bias m int 2147483647 N/A 0.0001 800000
/data_01/ku/range_ocean_mle3_compression_qual quality flag for 1 Hz altimeter data: Ku band range (MLE3 retracking) N/A byte 127 N/A 1 N/A
/data_01/ku/range_ocean_mle3_numval number of valid points for Ku band range (MLE3 retracking) count byte 127 0 to 20 1 N/A
/data_01/ku/range_ocean_mle3_rms Compression of Ku band high rate elements is preceded by a detection of outliers. Only valid high-rate values are used to compute this element m short 32767 N/A 0.0001 N/A
/data_01/ku/range_ocean_numval number of valid points for Ku band range count byte 127 0 to 20 1 N/A
/data_01/ku/range_ocean_rms Compression of Ku band high rate elements is preceded by a detection of outliers. Only valid high-rate values are used to compute this element m short 32767 N/A 0.0001 N/A
/data_01/ku/sea_state_bias A sea state bias correction must be added (negative value) to the instrument range to correct this range measurement for sea state delays of the radar pulse. This element should not be used over land. See SWOT Nadir Altimeter User Handbook m short 32767 N/A 0.0001 N/A
/data_01/ku/sea_state_bias_3d_mp2 Sea state bias computed from 3D model with mean wave period (T02) as third input. A sea state bias correction must be added (negative value) to the instrument range to correct this range measurement for sea state delays of the radar pulse. This element should not be used over land. See SWOT Nadir Altimeter User Handbook m short 32767 N/A 0.0001 N/A
/data_01/ku/sea_state_bias_adaptive A sea state bias correction must be added (negative value) to the instrument range to correct this range measurement for sea state delays of the radar pulse. This element should not be used over land. See SWOT Nadir Altimeter User Handbook m short 32767 N/A 0.0001 N/A
/data_01/ku/sea_state_bias_adaptive_3d_mp2 Sea state bias computed from 3D model with mean wave period (T02) as third input. A sea state bias correction must be added (negative value) to the instrument range to correct this range measurement for sea state delays of the radar pulse. This element should not be used over land. See SWOT Nadir Altimeter User Handbook m short 32767 N/A 0.0001 N/A
/data_01/ku/sea_state_bias_mle3 A sea state bias correction must be added (negative value) to the instrument range to correct this range measurement for sea state delays of the radar pulse. This element should not be used over land. See SWOT Nadir Altimeter User Handbook m short 32767 N/A 0.0001 N/A
/data_01/ku/sig0_adaptive All instrumental corrections included, excepted the system bias, i.e. AGC instrumental errors correction, internal calibration correction (sig0_cor_calibration) and atmospheric attenuation (sig0_cor_atm) dB short 32767 N/A 0.01 N/A
/data_01/ku/sig0_adaptive_compression_qual quality flag for 1 Hz altimeter data: Ku band backscatter coefficient (adaptive retracking) N/A byte 127 N/A 1 N/A
/data_01/ku/sig0_adaptive_numval number of valid points used to compute Ku band backscatter coefficient (adaptive retracking) count byte 127 0 to 20 1 N/A
/data_01/ku/sig0_adaptive_rms Compression of Ku band high rate elements is preceded by a detection of outliers. Only valid high-rate values are used to compute this element dB short 32767 N/A 0.01 N/A
/data_01/ku/sig0_cor_adaptive_net_instr Sum of AGC instrumental errors correction, internal calibration correction (sig0_cor_calibration) - system bias not included dB short 32767 N/A 0.01 N/A
/data_01/ku/sig0_cor_atm Based either on the radiometer (if available) or atmospheric model (otherwise). The flag sig0_cor_atm_source indicates whether the atmospheric model has been used dB short 32767 N/A 0.01 N/A
/data_01/ku/sig0_cor_ocean_mle3_net_instr Sum of AGC instrumental errors correction, internal calibration correction (sig0_cor_calibration) and modeled instrumental errors correction (sig0_cor_ocean_mle3_model_instr) - system bias not included dB short 32767 N/A 0.01 N/A
/data_01/ku/sig0_cor_ocean_net_instr Sum of AGC instrumental errors correction, internal calibration correction (sig0_cor_calibration) and modeled instrumental errors correction (sig0_cor_ocean_model_instr) - system bias not included dB short 32767 N/A 0.01 N/A
/data_01/ku/sig0_cor_ocean_net_instr_qual Threshold control of sig0_cor_ocean_net_instr N/A byte 127 N/A 1 N/A
/data_01/ku/sig0_ocean All instrumental corrections included, excepted the system bias, i.e. AGC instrumental errors correction, internal calibration correction (sig0_cor_calibration), modeled instrumental errors correction (sig0_cor_ocean_model_instr) and atmospheric attenuation (sig0_cor_atm) dB short 32767 N/A 0.01 N/A
/data_01/ku/sig0_ocean_compression_qual quality flag for 1 Hz altimeter data: Ku band backscatter coefficient N/A byte 127 N/A 1 N/A
/data_01/ku/sig0_ocean_mle3 All instrumental corrections included, excepted the system bias, i.e. AGC instrumental errors correction, internal calibration correction (sig0_cor_calibration), modeled instrumental errors correction (sig0_cor_ocean_mle3_model_instr) and atmospheric attenuation (sig0_cor_atm) dB short 32767 N/A 0.01 N/A
/data_01/ku/sig0_ocean_mle3_compression_qual quality flag for 1 Hz altimeter data: Ku band backscatter coefficient (MLE3 retracking) N/A byte 127 N/A 1 N/A
/data_01/ku/sig0_ocean_mle3_numval number of valid points used to compute Ku band backscatter coefficient (MLE3 retracking) count byte 127 0 to 20 1 N/A
/data_01/ku/sig0_ocean_mle3_rms Compression of Ku band high rate elements is preceded by a detection of outliers. Only valid high-rate values are used to compute this element dB short 32767 N/A 0.01 N/A
/data_01/ku/sig0_ocean_numval number of valid points used to compute Ku band backscatter coefficient count byte 127 0 to 20 1 N/A
/data_01/ku/sig0_ocean_rms Compression of Ku band high rate elements is preceded by a detection of outliers. Only valid high-rate values are used to compute this element dB short 32767 N/A 0.01 N/A
/data_01/ku/ssha = altitude of satellite (/data_01/altitude) - Ku band corrected altimeter range (range_ocean) - filtered altimeter ionospheric correction on Ku band (iono_cor_alt_filtered) - model dry tropospheric correction (/data_01/model_dry_tropo_cor_zero_altitude) - radiometer wet tropospheric correction (/data_01/rad_wet_tropo_cor) - sea state bias correction in Ku band (sea_state_bias) - solid earth tide height (/data_01/solid_earth_tide) - geocentric ocean tide height from FES solution (/data_01/ocean_tide_fes) - non-equilibrium long-period ocean tide height (/data_01/ocean_tide_non_eq) - geocentric pole tide height (/data_01/pole_tide) - internal tide (/data_01/internal_tide_hret) - dynamic atmospheric correction (/data_01/dac) - mean sea surface from CNES/CLS solution (/data_01/mean_sea_surface_cnescls). Set to default if the waveform classification (wvf_main_class) is not set to 1 = brown ocean, 12 = shifted brown, 13 = brown noise leading edge or 15 = linear positive_slope, or if the radiometer wet tropospheric interpolation quality flag (/data_01/rad_wet_tropo_cor_interp_qual) is set to 2 = fail m short 32767 N/A 0.001 N/A
/data_01/ku/ssha_mle3 = altitude of satellite (/data_01/altitude) - Ku band corrected altimeter range (range_ocean_mle3) - filtered altimeter ionospheric correction on Ku band (iono_cor_alt_filtered_mle3) - model dry tropospheric correction (/data_01/model_dry_tropo_cor_zero_altitude) - radiometer wet tropospheric correction (/data_01/rad_wet_tropo_cor) - sea state bias correction in Ku band (sea_state_bias_mle3) - solid earth tide height (/data_01/solid_earth_tide) - geocentric ocean tide height from FES solution (/data_01/ocean_tide_fes) - non-equilibrium long-period ocean tide height (/data_01/ocean_tide_non_eq) - geocentric pole tide height (/data_01/pole_tide) - internal tide (/data_01/internal_tide_hret) - dynamic atmospheric correction (/data_01/dac) - mean sea surface from CNES/CLS solution (/data_01/mean_sea_surface_cnescls). Set to default if the waveform classification (wvf_main_class) is not set to 1 = brown ocean, 12 = shifted brown, 13 = brown noise leading edge or 15 = linear positive_slope, or if the radiometer wet tropospheric interpolation quality flag (/data_01/rad_wet_tropo_cor_interp_qual) is set to 2 = fail m short 32767 N/A 0.001 N/A
/data_01/ku/swh_adaptive Ku band corrected significant waveheight (adaptive retracking) m short 32767 N/A 0.001 N/A
/data_01/ku/swh_adaptive_compression_qual quality flag for 1 Hz altimeter data: Ku band SWH (adaptive retracking) N/A byte 127 N/A 1 N/A
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