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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: 2026-06-01

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_20/c/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 (/data_01/c/range_cor_internal_path), Doppler correction (/data_01/c/range_cor_doppler), modeled instrumental errors correction (/data_01/c/range_cor_ocean_model_instr) and system bias m int 2147483647 N/A 0.0001 800000
/data_20/c/range_ocean_compression_qual Map of valid points used to compute the 1 Hz C band altimeter range N/A byte 127 N/A 1 N/A
/data_20/c/range_ocog Distance antenna-COG (/data_01/range_cor_cog), USO drift correction (/data_01/range_cor_uso), internal path correction (/data_01/c/range_cor_internal_path), Doppler correction (/data_01/c/range_cor_doppler) and system bias included m int 2147483647 N/A 0.0001 800000
/data_20/c/sig0_ice2 AGC instrumental errors correction and internal calibration correction (/data_01/c/sig0_cor_calibration) included dB short 32767 N/A 0.01 N/A
/data_20/c/sig0_leading_edge_ice2 AGC instrumental errors correction and internal calibration correction (/data_01/c/sig0_cor_calibration) included dB short 32767 N/A 0.01 N/A
/data_20/c/sig0_ocean All instrumental corrections included, excepted the system bias, i.e. AGC instrumental errors correction, internal calibration correction (/data_01/c/sig0_cor_calibration), modeled instrumental errors correction (/data_01/c/sig0_cor_ocean_model_instr) and atmospheric attenuation (sig0_cor_atm) dB short 32767 N/A 0.01 N/A
/data_20/c/sig0_ocean_compression_qual Map of valid points used to compute the 1 Hz C band backscatter coefficient N/A byte 127 N/A 1 N/A
/data_20/c/sig0_ocog AGC instrumental errors correction and internal calibration correction (/data_01/c/sig0_cor_calibration) included dB short 32767 N/A 0.01 N/A
/data_20/c/sigmal_ice2 The width of the leading edge corresponds to the so-called composite sigma (SigmaL) m short 32767 N/A 0.001 N/A
/data_20/c/slope1_ice2 20 Hz slope of the first part of the logarithm of the C band trailing edge (ice-2 retracking) s-1 int 2147483647 N/A 1 N/A
/data_20/c/slope2_ice2 20 Hz slope of the second part of the logarithm of the C band trailing edge (ice-2 retracking) s-1 int 2147483647 N/A 1 N/A
/data_20/c/swh_ocean All instrumental corrections included, i.e. modeled instrumental errors correction (/data_01/c/swh_cor_ocean_model_instr) and system bias m short 32767 N/A 0.001 N/A
/data_20/c/swh_ocean_compression_qual Map of valid points used to compute the 1 Hz C band significant waveheight N/A byte 127 N/A 1 N/A
/data_20/distance_to_coast 20 Hz distance to the coast m int 2147483647 N/A 1 N/A
/data_20/index_1hz_measurement Record counter of the averaged 1 Hz measurement associated to the 20 Hz elementary measurement N/A int 2147483647 N/A 1 N/A
/data_20/ku/ice2_qual ice-2 retracking quality flag N/A byte 127 N/A 1 N/A
/data_20/ku/mqe_adaptive Mean Quadratic Error between the waveforms samples and the corresponding model samples built from the adaptive retracking outputs 1 short 32767 N/A 0.0001 N/A
/data_20/ku/mqe_ice2 Mean Quadratic Error between the waveforms samples and the corresponding model samples built from the ice-2 retracking outputs 1 int 2147483647 N/A 1.0E-5 N/A
/data_20/ku/mqe_ocean Mean Quadratic Error between the waveforms samples and the corresponding model samples built from the ocean retracking outputs 1 short 32767 N/A 0.0001 N/A
/data_20/ku/mqe_ocean_mle3 Mean Quadratic Error between the waveforms samples and the corresponding model samples built from the MLE3 retracking outputs 1 short 32767 N/A 0.0001 N/A
/data_20/ku/num_iterations_adaptive 20 Hz number of iterations of the adaptive retracking in Ku band count short 32767 N/A 1 N/A
/data_20/ku/num_iterations_ocean 20 Hz number of iterations of the ocean retracking in Ku band count byte 127 N/A 1 N/A
/data_20/ku/num_iterations_ocean_mle3 20 Hz number of iterations of the ocean retracking in Ku band (MLE3 retracking) count byte 127 N/A 1 N/A
/data_20/ku/ocog_qual OCOG retracking quality flag N/A byte 127 N/A 1 N/A
/data_20/ku/off_nadir_angle_wf_ocean 20 Hz square of the off nadir angle computed from Ku band waveforms degrees^2 short 32767 N/A 0.0001 N/A
/data_20/ku/off_nadir_angle_wf_ocean_compression_qual Map of valid points used to compute the 1 Hz square of the off nadir angle computed from Ku band waveforms N/A byte 127 N/A 1 N/A
/data_20/ku/peakiness 20 Hz peakiness on Ku band waveforms 1 int 2147483647 N/A 0.001 N/A
/data_20/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 (/data_01/ku/range_cor_internal_path), Doppler correction (/data_01/ku/range_cor_doppler) and system bias m int 2147483647 N/A 0.0001 800000
/data_20/ku/range_adaptive_compression_qual Map of valid points used to compute the 1 Hz Ku band altimeter range N/A byte 127 N/A 1 N/A
/data_20/ku/range_ice2 Distance antenna-COG (/data_01/range_cor_cog), USO drift correction (/data_01/range_cor_uso), internal path correction (/data_01/ku/range_cor_internal_path), Doppler correction (/data_01/ku/range_cor_doppler) and system bias included m int 2147483647 N/A 0.0001 800000
/data_20/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 (/data_01/ku/range_cor_internal_path), Doppler correction (/data_01/ku/range_cor_doppler), modeled instrumental errors correction (/data_01/ku/range_cor_ocean_model_instr) and system bias m int 2147483647 N/A 0.0001 800000
/data_20/ku/range_ocean_compression_qual Map of valid points used to compute the 1 Hz Ku band altimeter range N/A byte 127 N/A 1 N/A
/data_20/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 (/data_01/ku/range_cor_internal_path), Doppler correction (/data_01/ku/range_cor_doppler), modeled instrumental errors correction (/data_01/ku/range_cor_ocean_mle3_model_instr) and system bias m int 2147483647 N/A 0.0001 800000
/data_20/ku/range_ocean_mle3_compression_qual Map of valid points used to compute the 1 Hz Ku band altimeter range N/A byte 127 N/A 1 N/A
/data_20/ku/range_ocog Distance antenna-COG (/data_01/range_cor_cog), USO drift correction (/data_01/range_cor_uso), internal path correction (/data_01/ku/range_cor_internal_path), Doppler correction (/data_01/ku/range_cor_doppler) and system bias included m int 2147483647 N/A 0.0001 800000
/data_20/ku/range_seaice Distance antenna-COG (/data_01/range_cor_cog), USO drift correction (/data_01/range_cor_uso), internal path correction (/data_01/ku/range_cor_internal_path), Doppler correction (/data_01/ku/range_cor_doppler) and system bias included m int 2147483647 N/A 0.0001 800000
/data_20/ku/range_tfmra Distance antenna-COG (/data_01/range_cor_cog), USO drift correction (/data_01/range_cor_uso), internal path correction (/data_01/ku/range_cor_internal_path), Doppler correction (/data_01/ku/range_cor_doppler) and system bias included m int 2147483647 N/A 0.0001 800000
/data_20/ku/seaice_qual sea-ice retracking quality flag N/A byte 127 N/A 1 N/A
/data_20/ku/sig0_adaptive All instrumental corrections included, excepted the system bias, i.e. AGC instrumental errors correction, internal calibration correction (/data_01/ku/sig0_cor_calibration) and atmospheric attenuation (sig0_cor_atm) dB short 32767 N/A 0.01 N/A
/data_20/ku/sig0_adaptive_compression_qual Map of valid points used to compute the 1 Hz Ku band backscatter coefficient N/A byte 127 N/A 1 N/A
/data_20/ku/sig0_ice2 AGC instrumental errors correction and internal calibration correction (/data_01/ku/sig0_cor_calibration) included dB short 32767 N/A 0.01 N/A
/data_20/ku/sig0_leading_edge_ice2 AGC instrumental errors correction and internal calibration correction (/data_01/ku/sig0_cor_calibration) included dB short 32767 N/A 0.01 N/A
/data_20/ku/sig0_ocean All instrumental corrections included, excepted the system bias, i.e. AGC instrumental errors correction, internal calibration correction (/data_01/ku/sig0_cor_calibration), modeled instrumental errors correction (/data_01/ku/sig0_cor_ocean_model_instr) and atmospheric attenuation (sig0_cor_atm) dB short 32767 N/A 0.01 N/A
/data_20/ku/sig0_ocean_compression_qual Map of valid points used to compute the 1 Hz Ku band backscatter coefficient N/A byte 127 N/A 1 N/A
/data_20/ku/sig0_ocean_mle3 All instrumental corrections included, excepted the system bias, i.e. AGC instrumental errors correction, internal calibration correction (/data_01/ku/sig0_cor_calibration), modeled instrumental errors correction (/data_01/ku/sig0_cor_ocean_mle3_model_instr) and atmospheric attenuation (sig0_cor_atm) dB short 32767 N/A 0.01 N/A
/data_20/ku/sig0_ocean_mle3_compression_qual Map of valid points used to compute the 1 Hz Ku band backscatter coefficient N/A byte 127 N/A 1 N/A
/data_20/ku/sig0_ocog AGC instrumental errors correction and internal calibration correction (/data_01/ku/sig0_cor_calibration) included dB short 32767 N/A 0.01 N/A
/data_20/ku/sig0_seaice AGC instrumental errors correction and internal calibration correction (/data_01/ku/sig0_cor_calibration) included dB short 32767 N/A 0.01 N/A
/data_20/ku/sig0_tfmra AGC instrumental errors correction and internal calibration correction (/data_01/ku/sig0_cor_calibration) included dB short 32767 N/A 0.01 N/A
/data_20/ku/sigmal_ice2 The width of the leading edge corresponds to the so-called composite sigma (SigmaL) m short 32767 N/A 0.001 N/A
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