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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/swh_adaptive_numval 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 count byte 127 0 to 20 1 N/A
/data_01/ku/swh_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 0.001 N/A
/data_01/ku/swh_cor_adaptive_net_instr Set to zero m short 32767 N/A 0.001 N/A
/data_01/ku/swh_cor_ocean_mle3_net_instr Sum of modeled instrumental errors correction (swh_cor_ocean_mle3_model_instr) and system bias m short 32767 N/A 0.001 N/A
/data_01/ku/swh_cor_ocean_net_instr Sum of modeled instrumental errors correction (swh_cor_ocean_model_instr) and system bias m short 32767 N/A 0.001 N/A
/data_01/ku/swh_cor_ocean_net_instr_qual Threshold control of swh_cor_ocean_net_instr N/A byte 127 N/A 1 N/A
/data_01/ku/swh_ocean All instrumental corrections included, i.e. modeled instrumental errors correction (swh_cor_ocean_model_instr) and system bias m short 32767 N/A 0.001 N/A
/data_01/ku/swh_ocean_compression_qual quality flag for 1 Hz altimeter data: Ku band SWH N/A byte 127 N/A 1 N/A
/data_01/ku/swh_ocean_mle3 All instrumental corrections included, i.e. modeled instrumental errors correction (swh_cor_ocean_mle3_model_instr) and system bias m short 32767 N/A 0.001 N/A
/data_01/ku/swh_ocean_mle3_compression_qual quality flag for 1 Hz altimeter data: Ku band SWH (MLE3 retracking) N/A byte 127 N/A 1 N/A
/data_01/ku/swh_ocean_mle3_numval number of valid points used to compute Ku band significant waveheight (MLE3 retracking) count byte 127 0 to 20 1 N/A
/data_01/ku/swh_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 0.001 N/A
/data_01/ku/swh_ocean_numval number of valid points used to compute Ku band significant waveheight count byte 127 0 to 20 1 N/A
/data_01/ku/swh_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 0.001 N/A
/data_01/ku/wvf_main_class Waveform classification : main class selected by classification neural network trained on shape features of the waveforms N/A byte 127 N/A 1 N/A
/data_01/latitude Positive latitude is North latitude, negative latitude is South latitude. See SWOT Nadir Altimeter User Handbook. Associated quality flag is orb_state_diode_flag for the OGDR products, orb_state_rest_flag for the IGDR and GDR products degrees_north int 2147483647 N/A 1.0E-6 N/A
/data_01/load_tide_fes This value contains the total load tide height (short-period and long-period) for the geocentric ocean tide (FES solution). To get only the ocean tide height (FES solution), do: ocean_tide_fes + ocean_tide_non_eq - load_tide_fes. See SWOT Nadir Altimeter User Handbook m short 32767 N/A 0.0001 N/A
/data_01/load_tide_got This value has already been added to the corresponding ocean tide height value recorded in the product (ocean_tide_got). See SWOT Nadir Altimeter User Handbook m short 32767 N/A 0.0001 N/A
/data_01/longitude East longitude relative to Greenwich meridian. See SWOT Nadir Altimeter User Handbook. Associated quality flag is orb_state_diode_flag for the OGDR products, orb_state_rest_flag for the IGDR and GDR products degrees_east int 2147483647 N/A 1.0E-6 N/A
/data_01/mean_dynamic_topography See SWOT Nadir Altimeter User Handbook m int 2147483647 N/A 0.0001 N/A
/data_01/mean_dynamic_topography_interp_qual MDT interpolation flag N/A byte 127 N/A 1 N/A
/data_01/mean_sea_surface_cnescls See SWOT Nadir Altimeter User Handbook m int 2147483647 N/A 0.0001 N/A
/data_01/mean_sea_surface_cnescls_interp_qual mean sea surface interpolation flag (CNES/CLS solution) N/A byte 127 N/A 1 N/A
/data_01/mean_sea_surface_dtu See SWOT Nadir Altimeter User Handbook m int 2147483647 N/A 0.0001 N/A
/data_01/mean_sea_surface_dtu_interp_qual mean sea surface interpolation flag (DTU solution) N/A byte 127 N/A 1 N/A
/data_01/mean_wave_direction mean direction of the sea surface wave degrees int 2147483647 N/A 0.01 N/A
/data_01/mean_wave_period_t02 t02 mean wave period s short 32767 N/A 0.01 N/A
/data_01/meteo_map_availability_flag Possible values are: 0 meaning ’2 maps, nominal’ (six hours apart), 1 meaning ’2 maps, degraded’ (more than six hours apart), 2 meaning ’1 map, closest map used’, 3 meaning ’no valid map’ N/A byte 127 N/A 1 N/A
/data_01/meteo_measurement_altitude_interp_qual 0 = interpolation from 4 points; 1 = interpolation from less than 4 points N/A byte 127 N/A 1 N/A
/data_01/meteo_zero_altitude_interp_qual 0 = interpolation from 4 points; 1 = interpolation from less than 4 points N/A byte 127 N/A 1 N/A
/data_01/model_dry_tropo_cor_measurement_altitude Computed at coarse DEM altitude (for O&amp;IGDR) or precise measurement altitude (for GDR) at the altimeter time-tag from the interpolation of 2 meteorological fields that surround the altimeter time-tag. A dry tropospheric correction must be added (negative value) to the instrument range to correct this range measurement for dry tropospheric range delays of the radar pulse. See SWOT Nadir Altimeter User Handbook m short 32767 N/A 0.0001 N/A
/data_01/model_dry_tropo_cor_zero_altitude Computed at Mean Sea Level Pressure at the altimeter time-tag from the interpolation of 2 meteorological fields that surround the altimeter time-tag. A dry tropospheric correction must be added (negative value) to the instrument range to correct this range measurement for dry tropospheric range delays of the radar pulse. See SWOT Nadir Altimeter User Handbook m short 32767 N/A 0.0001 N/A
/data_01/model_wet_tropo_cor_measurement_altitude Computed at coarse DEM altitude (for O&amp;IGDR) or precise measurement altitude (for GDR) at the altimeter time-tag from the interpolation of 2 meteorological fields that surround the altimeter time-tag. A wet tropospheric correction must be added (negative value) to the instrument range to correct this range measurement for wet tropospheric range delays of the radar pulse. See SWOT Nadir Altimeter User Handbook m short 32767 N/A 0.0001 N/A
/data_01/model_wet_tropo_cor_zero_altitude Computed at coarse DEM altitude at the altimeter time-tag from the interpolation of 2 meteorological fields that surround the altimeter time-tag. A wet tropospheric correction must be added (negative value) to the instrument range to correct this range measurement for wet tropospheric range delays of the radar pulse. See SWOT Nadir Altimeter User Handbook m short 32767 N/A 0.0001 N/A
/data_01/numtotal_20hz_measurement Total number of 20 Hz measurements associated to the 1 Hz measurement N/A byte 127 N/A 1 N/A
/data_01/ocean_tide_eq This value has already been added to the two geocentric ocean tide height values recorded in the product (ocean_tide_got and ocean_tide_fes). The permanent tide (zero frequency) is not included in this parameter because it is included in the geoid and mean sea surface (geoid, mean_sea_surface_cnescls). See SWOT Nadir Altimeter User Handbook m short 32767 N/A 0.0001 N/A
/data_01/ocean_tide_fes Includes the equilibrium long-period ocean tide height (ocean_tide_eq) and only the short-period part of the corresponding loading tide (load_tide_fes). The permanent tide (zero frequency) is not included in this parameter because it is included in the geoid and mean sea surface (geoid, mean_sea_surface_cnescls). To get the total geocentric tide height (FES solution), do: ocean_tide_fes + ocean_tide_non_eq. See SWOT Nadir Altimeter User Handbook m int 2147483647 N/A 0.0001 N/A
/data_01/ocean_tide_fes_interp_qual 0 = 4 points over ocean; 1 = less than 4 points; 2 = extrapolated points N/A byte 127 N/A 1 N/A
/data_01/ocean_tide_got Includes the corresponding loading tide (load_tide_got) and equilibrium long-period ocean tide height (ocean_tide_eq). The permanent tide (zero frequency) is not included in this parameter because it is included in the geoid and mean sea surface (geoid, mean_sea_surface_cnescls). See SWOT Nadir Altimeter User Handbook m int 2147483647 N/A 0.0001 N/A
/data_01/ocean_tide_got_interp_qual 0 = 4 points over ocean; 1 = less than 4 points; 2 = extrapolated points N/A byte 127 N/A 1 N/A
/data_01/ocean_tide_non_eq This parameter is computed as a correction to the parameter ocean_tide_eq; it contains the long-period ocean tide and the long-period load tide components. This value can be added to ocean_tide_eq (or ocean_tide_got, ocean_tide_fes) so that the resulting value models the total non equilibrium ocean tide height. See SWOT Nadir Altimeter User Handbook m short 32767 N/A 0.0001 N/A
/data_01/orb_state_diode_flag 0 = Accurate orbit (0 - 5 cm radial), 1 = Good orbit (5 - 10 cm radial), 2 = Moderate orbit (10 - 15 cm radial), 4-8 = Potentially degraded orbit (&gt; 15 cm radial), 9 = Degraded orbit (e.g., as during maneuver) N/A byte 127 N/A 1 N/A
/data_01/orb_state_rest_flag 0 characterizes a mission operations orbit that is computed during a maneuver period, 1 stands for an adjusted mission operations orbit, 2 stands for an extrapolated mission operations orbit, 3 stands for an adjusted (preliminary/precise) orbit, 4 indicates that the (preliminary/precise) orbit is estimated during a maneuver period, 5 indicates that the (preliminary/precise) orbit is interpolated over a tracking data gap, 6 means that the (preliminary/precise) orbit is extrapolated for a duration less than 1 day, 7 means that the (preliminary/precise) orbit is extrapolated for a duration that ranges from 1 day to 2 days, 8 means that the (preliminary/precise) orbit is extrapolated for a duration larger than 2 days, or that the orbit is extrapolated just after a maneuver, 9 stands for the DORIS DIODE navigator orbit. The nominal value is 3 N/A byte 127 N/A 1 N/A
/data_01/pole_tide See SWOT Nadir Altimeter User Handbook m short 32767 N/A 0.0001 N/A
/data_01/rad_cloud_liquid_water Should not be used over land kg/m^2 short 32767 N/A 0.01 N/A
/data_01/rad_side_1_distance_to_land Shortest distance between nadir sub-satellite point and land m int 2147483647 N/A 1 N/A
/data_01/rad_side_1_land_frac_187 ratio between 0 and 1 1 short 32767 N/A 0.01 N/A
/data_01/rad_side_1_land_frac_238 ratio between 0 and 1 1 short 32767 N/A 0.01 N/A
/data_01/rad_side_1_land_frac_340 ratio between 0 and 1 1 short 32767 N/A 0.01 N/A
/data_01/rad_side_1_rain_flag See SWOT Nadir Altimeter User Handbook N/A byte 127 N/A 1 N/A
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