ARIA Sentinel-1 Geocoded Unwrapped Interferogram (GUNW)

Product Overview

The ARIA Sentinel-1 Geocoded Unwrapped Interferogram (ARIA-S1-GUNW) product is a standardized interferometric SAR (InSAR) dataset that enables rapid analysis of surface deformation using Sentinel-1 SAR data. Produced by JPL’s ARIA project, it provides CF-compliant NetCDF files at 90-m pixel spacing, containing unwrapped interferometric phase measurements, imaging geometry, various correction layers, and metadata. It was originally formulated under GRFN (Getting Ready For Nisar). Specifically, the ARIA Standard Displacement Product is a Geocoded Unwrapped Interferogram (GUNW IFG) product derived from the European Space Agency’s Sentinel-1 Single Look Complex (SLC) Interferometric Wide (IW) Data Products with VV Polarization. IGARSS 2023 GUNW Paper has an overview of the product and example applications.

2019 Ridgecrest Earthquake - Wrapped Phase Example: 2019 California Ridgecrest earthquake showing wrapped interferometric phase

Target Applications

Earthquakes
Volcanoes - see Wang et al. on Volcanoes in the Aleutian Chain
Landslides
Ground Water Monitoring
Sea-level rise and subsidence - see Buzzunga et al. about subsidence along the coast of North Carolina

Data Access

GUNW products are available through:

Alaska Satellite Facility (ASF) DAAC - ARIA-S1-GUNW products

On-Demand Processing

On-Demand Processing via Hyp3 - free processing allotments for all users, anywhere in the world.

Additional Tools and References

DockerizedTopsApp - this is the open source workflow that we use to generate the ARIA-S1-GUNW
ARIA-tools - Download, prepare, and analyze GUNW products for use with MintPy
MintPy - displacement time-series analysis toolbox
OPERA Cal/Val Disasters - Disaster response workflows
OPERA Applications - Application examples

Product Structure

The GUNW product is organized as a hierarchical NetCDF file with the following structure:

GUNW NetCDF File
│
├── science/
    ├── grids/
    │   ├── data/                          (0.00083333° or ~90 m at equator)
    │   │   ├── unwrappedPhase             Phase in radians
    │   │   ├── coherence                  Filtered coherence (0-1)
    │   │   ├── connectedComponents        Snaphu connected components
    │   │   ├── amplitude                  SAR amplitude (power)
    │   │   └── unfilteredCoherence        Unfiltered coherence (New in v3.0.0+)
    │   │
    │   ├── imagingGeometry/               (0.1° or ~11 km at equator)
    │   │   ├── incidenceAngle             Incidence angle (degrees)
    │   │   ├── azimuthAngle               Azimuth angle (degrees)
    │   │   ├── lookAngle                  Look angle (degrees)
    │   │   ├── perpendicularBaseline      Perpendicular baseline (meters)
    │   │   └── parallelBaseline           Parallel baseline (meters)
    │   │
    │   └── corrections/
    │       ├── derived/
    │       │   ├── ionosphere/            (0.00916° or ~1 km - NEW in v3.0.0+)
    │       │   │   └── ionosphere         Ionospheric phase correction (rad)
    │       │   │
    │       │   └── ionosphereBurstRamps/  (0.00083333° or ~90 m - NEW in v3.0.0+)
    │       │       └── ionosphereBurstRamps  Burst ramps due to ionosphere (rad)
    │       │
    │       └── external/
    │           ├── troposphere/           (URLs to external files if available)
    │           │   ├── troposphereHydrostatic
    │           │   └── troposphereWet
    │           │
    │           └── tides/
    │               └── solidEarth/        (0.1° or ~11 km - NEW in v3.0)
    │                   ├── reference/
    │                   │   └── solidEarthTide  (radians)
    │                   └── secondary/
    │                       └── solidEarthTide  (radians)
    │
    └── radarMetaData/
        ├── wavelength
        ├── centerFrequency
        ├── ISCEversion
        ├── unwrapMethod
        ├── DEM
        ├── azimuthZeroDopplerStartTime
        ├── azimuthZeroDopplerEndTime
        └── inputSLC/
            ├── reference/
            │   ├── L1InputGranules
            │   └── orbitType
            └── secondary/
                ├── L1InputGranules
                └── orbitType

Data Layers

Core Data Layers (90 m resolution)

unwrappedPhase: Unwrapped interferometric phase in radians
coherence: Filtered coherence (Goldstein filtered)
connectedComponents: Snaphu connected components for quality assessment
amplitude: InSAR amplitude (power)
unfilteredCoherence: Coherence without filtering (v3.0.0+)

Correction Layers

Ionosphere Corrections (NEW in v3.0.0+)

ionosphere (~1 km resolution): Estimated ionospheric phase correction using split-spectrum method
ionosphereBurstRamps (90 m resolution): Burst-specific ionospheric ramp corrections

Solid Earth Tide Corrections (v3.0.0+)

solidEarthTide (~11 km resolution): Solid Earth tide phase corrections for both reference and secondary acquisitions

Tropospheric Corrections

troposphereHydrostatic: URL to hydrostatic tropospheric delay correction (if available via RAiDER/HRRR) - product must be over Continental United States
troposphereWet: URL to wet tropospheric delay correction (if available via RAiDER/HRRR) - product must be over Continental United States

Geometry Layers (~11 km resolution)

incidenceAngle: SAR incidence angle (degrees)
azimuthAngle: SAR azimuth angle (degrees)
lookAngle: SAR look angle (degrees)
parallelBaseline: Parallel baseline (meters)
perpendicularBaseline: Perpendicular baseline (meters)

All geometry layers are 3D arrays with dimensions (height × latitude × longitude) to account for topographic variation.

File Naming Convention

GUNW files follow a standardized naming scheme:

S1-GUNW-A-R-161-tops-20260311_20260305-173318-00002E_00050N-PP-8c32-v3_0_1.nc

Naming Components

Component	Example	Description
Product Type	`S1-GUNW`	Sentinel-1 Geocoded Unwrapped Interferogram
Flight Direction	`A`	Ascending (A) or Descending (D)
Look Direction	`R`	Right-looking (always R for Sentinel-1)
Track Number	`161`	Relative orbit / track number (3 digits, zero-padded)
Processing Mode	`tops`	TOPS processing mode (legacy constant)
Date Pair	`20260311_20260305`	Reference_Secondary dates (YYYYMMDD)
Center Time	`173318`	Reference center acquisition time (HHMMSS UTC)
Geographic Center	`00002E_00050N`	Longitude_Latitude of scene center (5 digits each) Format: `XXXXX[E\|W]_XXXXX[N\|S]`
Processing Type	`PP`	Post-processed (legacy constant)
Hash ID	`8c32`	MD5 hash (first 4 chars) of input granule IDs
Version	`v3_0_1`	Product version (current: 3.0.1)

Custom product prefix: For non-standard processing parameters, the prefix becomes S1-GUNW_CUSTOM instead of S1-GUNW.

Version History

Version 3.0.1 (Current)

Ionospheric correction layers (split-spectrum method)
Ionospheric burst ramp corrections
Solid Earth tide corrections
Unfiltered coherence layer
Enhanced metadata and CF-compliance
Tropospheric Correction over Continental United States using HRRR (via RAiDER)

Version 2.x

Standard displacement products

Applications

The GUNW product is designed for:

Earthquake deformation analysis
Volcanic eruption monitoring
Landslide detection and tracking
Groundwater/subsidence monitoring
Sea-level rise and subsidence studies
General surface deformation analysis

Standards Compliance

Format: NetCDF-4 (HDF5)
Convention: CF-1.6 (Climate and Forecast)
Projection: WGS 84 (EPSG:4326)
Grid: Geographic latitude/longitude
Resolution: 90 m (0.00083333°) for primary data layers

Reference papers

D. Bekaert et al., “The Aria-S1-Gunw: The ARIA Sentinel-1 Geocoded Unwrapped Phase Product for Open Insar Science and Disaster Response,” IGARSS 2023 - 2023 IEEE International Geoscience and Remote Sensing Symposium, Pasadena, CA, USA, 2023, pp. 2850-2853, https://doi.org/10.1109/IGARSS52108.2023.10282671. [Preprint Link]
Buzzanga, B., Bekaert. D.P.S., Hamlington, B.D. & Sangha, S.S., 2020, Towards sustained monitoring of subsidence at the coast using InSAR and GPS: An application in Hampton Roads, Virginia. Geophysical Research Letters, 47, https://doi.org/10.1029/2020GL090013