SAR data#

You will find a SAR tutorial here.

Implemented SAR constellations#

sar_sensors

Constellations

Class

Use archive

Capella

CapellaProduct

COSMO-Skymed 1st Generation

CskProduct

COSMO-Skymed 2nd Generation

CsgProduct

ICEYE

IceyeProduct

RADARSAT Constellation Mission

RcmProduct

RADARSAT-2

Rs2Product

✅ for ground range data, ❌ for complex data

Sentinel-1

S1Product

Sentinel-1 RTC

S1RtcProduct

✅ for ASF

SAOCOM-1

SaocomProduct

TerraSAR-X, TanDEM-X, PAZ SAR

TsxProduct

Warning

Satellites products that cannot be used as archived have to be extracted before use, mostly because SNAP doesn’t handle them.

Product type handling#

Constellations

Product Type

Handled

Capella

SLC

Capella

GEC

Capella

GEO

Capella

SICD, SIDD, CPHD

COSMO-Skymed

SCS

COSMO-SkyMed 1st Generation

DGM

COSMO-SkyMed 2nd Generation

DGM

COSMO-SkyMed

GEC, GTC

ICEYE

SLC

ICEYE

GRD

ICEYE

ORTHO

💤

RADARSAT Constellation Mission

SLC

RADARSAT Constellation Mission

GRC, GCC, GCD

RADARSAT Constellation Mission

GRD

RADARSAT-2

SLC

RADARSAT-2

SGX, SCN, SCW,
SCF, SCS, SSG, SPG

RADARSAT-2

SGF

Sentinel-1

SLC

Sentinel-1

GRD

Sentinel-1

RTC (ASF and MPC)

SAOCOM-1

SLC

SAOCOM-1

ID

SAOCOM-1

GEC

SAOCOM-1

GTC

TerraSAR-X, TanDEM-X, PAZ SAR

SSC

TerraSAR-X, TanDEM-X, PAZ SAR

MGD

TerraSAR-X, TanDEM-X, PAZ SAR

GEC

TerraSAR-X, TanDEM-X, PAZ SAR

EEC

✅: Tested
⚠: Never tested, use it at your own risk!
❌: Not handled
💤: Waiting for the release

The goal of EOReader is to implement every constellation that can be used in the Copernicus Emergency Management Service. The constellations that can be used during CEMS activations are (as of 09/2021):
cems_constellations

SAR Bands#

Warning

  • EOReader always loads SAR bands in a GRD format. This library is not (yet ?) meant to manage inSAR or other complex processes.

  • Only the Intensity bands are used (not the I, Q for complex data or Amplitude for ground range data)

  • Some SAR band may contain null pixels that are not really nodata (COSMO for example).
    In this case, the Terrain Correction step applied by SNAP can create large nodata area.
    If this is the case, you can set the keyword SAR_INTERP_NA to True when loading or stacking SAR data

According to what contains the products, allowed SAR bands are:

  • VV

  • VH

  • HH

  • HV

  • RH (only for RADARSAT-Constellation)

  • RV (only for RADARSAT-Constellation)

You also can load despeckled bands:

Available indices#

EOReader uses (from version 0.18.0) the indices described in the awesome spectral indices (ASI) project.

ASI implements SAR indices, with the list available here.

DEM bands#

These bands need a valid worldwide DEM path positioned thanks to the environment variable EOREADER_SAR_DEFAULT_RES

  • DEM

  • SLOPE

SAR constellations can only load DEM and SLOPE bands as the sun position does not impact SAR data. The SLOPE band is given in degrees. Please post an issue if you need this band in percent.

These bands need a valid worldwide DEM path positioned thanks to the environment variable EOREADER_DEM_PATH. You can use both a local path e.g. /mnt/dataserver/dems/srtm_30_v4/index.vrt or \\dataserver\DEMS\srtm_30_v4\index.vrt or a URL pointing to a web resources hosted on a S3 compatible storage e.g. https://s3.storage.com/dem-bucket/srtm_cog.tif (not available on Windows for now).

Default pixel size and resolution#

The default resolution of SAR products is the one given in Data Access Portfolio (2014-2022, section 6.2). For resolutions not available in this document, we are using the pixel spacing given by the constellation’s provider. Complex data are always converted back to ground range to be used, so the complex resolution is never used by EOReader.

The default pixel size of GRD bands is not the same as the product resolution! (i.e. pixel size of 10m with a resolution of 20m for Sentinel-1 IW data)

Warning

⚠ Pay attention that for a pixel spacing of 10 meters and a rg x az resolution of 23m, objects under 23m won’t be resolved ! As this may be counter-intuitive, it is recommanded to always specify the pixel size when loading SAR data.

Note

Resolution is not used in EOReader, only the pixel_size. Resolution is juste specified as an information. For now, resolutions are stored with only one number in EOReader (not rg x az, only one of the two, which will be in bold here after). If this needs change, don’t hesitate to write an issue :)

Sentinel-1#

Sentinel-1

Ground Range Detected (GRD)
Full Resolution (FR)

Ground Range Detected (GRD)
High Resolution (HR)

Ground Range Detected (GRD)
Medium Resolution (MR)

StripMap (SM)

pixel size: 3.5 m
rg x az resolution: 9.0 m

pixel size: 10.0 m
rg x az resolution: 23.0 m

pixel size: 40.0 m
rg x az resolution: 84.0 m

Interferometric Wide swath (IW)

pixel size: 10.0 m
rg x az resolution: 20.0 m

pixel size: 40.0 m
rg x az resolution: 88.0 x 87.0 m

Extra-Wide swath (EW)

pixel size: 25.0 m
rg x az resolution: 25.0 m

pixel size: 40.0 m
rg x az resolution: 93.0 x 87.0 m

Wave (WV)

pixel size: 25.0 m
rg x az resolution: 52.0 x 51.0 m

COSMO-Skymed 1st Generation#

COSMO-Skymed
1st Generation

Detected Ground Multi-look (DGM)
Geocoded Ellipsoid Corrected (GEC)
Geocoded Terrain Corrected (GTC)

Spotlight
Mode-2 (S2)

pixel size: 0.5 m
rg x az resolution: 1.0 m

StripMap
Himage from SCS (HI)

pixel size: 2.5 m
rg x az resolution: 3.0 m

StripMap
Himage GRD (HI)

pixel size: 2.5 m
rg x az resolution: 5.0 m

StripMap
PingPong (PP)

pixel size: 10.0 m
rg x az resolution: 20.0 m

ScanSAR
Wide Region (WR)

pixel size: 15.0 m
rg x az resolution: 30.0 m

ScanSAR
Huge Region (HR)

pixel size: 50.0 m
rg x az resolution: 100.0 m

COSMO-Skymed 2nd Generation#

COSMO-Skymed
2nd Generation

Detected Ground Multi-look (DGM)
Geocoded Ellipsoid Corrected (GEC)
Geocoded Terrain Corrected (GTC)

SPOTLIGHT 2A

Multilook ID: #1: pixel size: 0.15 m, rg x az resolution: 0.4 m
Multilook ID: #2: pixel size: 0.3 m, rg x az resolution: 0.7 m
Multilook ID: #3: pixel size: 0.45 m, rg x az resolution: 1.0 m

SPOTLIGHT 2B

Multilook ID: #1: pixel size: 0.25 m, rg x az resolution: 0.7 m
Multilook ID: #2: pixel size: 0.5 m, rg x az resolution: 1.2 m
Multilook ID: #3: pixel size: 1.0 m, rg x az resolution: 2.3 m

SPOTLIGHT 2C

Multilook ID: #1: pixel size: 0.3 m, rg x az resolution: 0.8 m
Multilook ID: #2: pixel size: 0.6 m, rg x az resolution: 1.4 m
Multilook ID: #3: pixel size: 0.9 m, rg x az resolution: 2.1 m

STRIPMAP & QUADPOL

Multilook ID: #1: pixel size: 1.25 m, rg x az resolution: 3.0 m
Multilook ID: #2: pixel size: 2.5 m, rg x az resolution: 5.6 m
Multilook ID: #3: pixel size: 5.0 m, rg x az resolution: 11.2 m

SCANSAR1

Multilook ID: #1: pixel size: 5.0 m, rg x az resolution: 20.0 m
Multilook ID: #2: pixel size: 10.0 m, rg x az resolution: 23.0 m
Multilook ID: #3: pixel size: 15.0 m, rg x az resolution: 35.0 m

SCANSAR2

Multilook ID: #1: pixel size: 10.0 m, rg x az resolution: 40.0 m
Multilook ID: #2: pixel size: 20.0 m, rg x az resolution: 47.0 m
Multilook ID: #3: pixel size: 50.0 m, rg x az resolution: 115.0 m

PINGPONG

Multilook ID: #1: pixel size: 2.0 m, rg x az resolution: 12.0 m
Multilook ID: #2: pixel size: 4.0 m, rg x az resolution: 12.0 m
Multilook ID: #3: pixel size: 10.0 m, rg x az resolution: 22.5 m

TerraSAR-X & TanDEM-X & PAZ SAR#

TerraSAR-X
TanDEM-X
PAZ SAR

Multi Look Ground Range (MGD)
Geocoded Ellipsoid Corrected (GEC)
Enhanced Ellipsoid Corrected (EEC)
Spatially enhanced

StripMap (SM)
Single-Pol

pixel size: 1.25 m
rg x az resolution: 3.3 m

StripMap (SM)
Dual-Pol

pixel size: 3.0 m
rg x az resolution: 6.6 m

High Resolution Spotlight (HS)
Single-Pol

pixel size: 0.5 m
rg x az resolution: 1.1 m

High Resolution Spotlight (HS)
Dual-Pol

pixel size: 1.0 m
rg x az resolution: 2.2 m

Spotlight (SL)
Single-Pol

pixel size: 0.75 m
rg x az resolution: 1.7 m

Spotlight (SL)
Dual-Pol

pixel size: 1.0 m
rg x az resolution: 3.4 m

Staring Spotlight (ST)
Single-Pol

pixel size: 0.2 m
rg x az resolution: 0.24 m

ScanSAR (SC)
Four Beams

pixel size: 8.25 m
rg x az resolution: 18.5 m

ScanSAR (SC)
Six Beams

pixel size: 15.0 m
rg x az resolution: 40.0 m

Note

All product types are used in high resolution (SE), as the high radiometry products are not used in Copernicus Emergency Management Service. This is not the case for ScanSAR products, always delivered in RE. If you want all the RE products implemented, don’t hesitate to write an issue :)

RADARSAT-2#

Classic modes#

RADARSAT-2

SAR georeferenced extra (SGX)

SAR georeferenced fine (SGF)

SAR systematic geocorrected(SSG)
SAR precision geocorrected (SPG)

Spotlight

pixel size: 0.8 m (1.0 if incidence angle < 48°)
rg x az resolution: 0.8 m

pixel size: 0.5 m
rg x az resolution: 0.8 m

pixel size: 0.5 m
rg x az resolution: 0.8 m

Ultra-Fine
Wide Ultra-Fine

pixel size: 0.8 m (1.0 if incidence angle < 48°)
rg x az resolution: 2.8 m

pixel size: 1.5625 m
rg x az resolution: 2.8 m

pixel size: 1.5625 m
rg x az resolution: 2.8 m

Multi-Look Fine
Wide Multi-Look Fine

pixel size: 3.125 m
rg x az resolution: 7.6 m

pixel size: 6.25 m
rg x az resolution: 7.6 m

pixel size: 6.25 m
rg x az resolution: 7.6 m

Extra-Fine /*

pixel size: 2.0 m
rg x az resolution: 4.6 m

pixel size: 3.125 m
rg x az resolution: 4.6 m

pixel size: 3.125 m
rg x az resolution: 4.6 m

Fine
Wide-Fine

pixel size: 3.125 m
rg x az resolution: 7.7 m

pixel size: 6.25 m
rg x az resolution: 7.7 m

pixel size: 6.25 m
rg x az resolution: 7.7 m

Standard
Wide

pixel size: 8.0 m
rg x az resolution: 24.7 m

pixel size: 12.5 m
rg x az resolution: 24.7 m

pixel size: 12.5 m
rg x az resolution: 24.7 m

Extended High

pixel size: 8.0 m
rg x az resolution: 24.7 m

pixel size: 12.5 m
rg x az resolution: 24.7 m

pixel size: 12.5 m
rg x az resolution: 24.7 m

Extended Low

pixel size: 10.0 m
rg x az resolution: 24.7 m

pixel size: 12.5 m
rg x az resolution: 24.7 m

pixel size: 12.5 m
rg x az resolution: 24.7 m

Fine Quad-Pol
Wide Quad-Pol

pixel size: 3.125 m
rg x az resolution: 7.6 m

pixel size: 3.125 m
rg x az resolution: 7.6 m

Standard Quad-Pol
Wide Standard Quad-Pol

pixel size: 8.0 m
rg x az resolution: 7.6 m

pixel size: 8.0 m
rg x az resolution: 7.6 m

  • Only the Extra-Fine mode with 1 look is taken into account. Pixel sizes can change with 4 or 28 looks.

ScanSAR mode#

RADARSAT-2

ScanSAR narrow beam (SCN)

ScanSAR wide beam (SCW)

ScanSAR fine (SCF)
ScanSAR sampled (SCS

ScanSAR Narrow

pixel size: 25.0 m
rg x az resolution: 50.0 m

pixel size: 25.0 m
rg x az resolution: 50.0 m

ScanSAR Wide

pixel size: 50.0 m
rg x az resolution: 100.0 m

pixel size: 50.0 m
rg x az resolution: 100.0 m

Other modes#

RADARSAT-2

From SLC

Other product types

Ship (Detection of vessels)

pixel size: 20.0 m
rg x az resolution: 35.0 m

pixel size: 40.0 m
rg x az resolution: 35.0 m

Ocean Surveillance

pixel size: 35.0 m
rg x az resolution: 50.0 m

pixel size: 50.0 m
rg x az resolution: 50.0 m

RADARSAT-Constellation#

RADARSAT-Constellation

Pixel size and Resolution

Spotlight [FSL]

pixel size: 0.33 m
rg x az resolution: 1.0 m

Very-High Resolution, 3 meters [3M]

pixel size: 1.25 m
rg x az resolution: 3.0 m

High Resolution, 5 meters [5M]

pixel size: 2.0 m
rg x az resolution: 5.0 m

Quad-Polarization [QP]

pixel size: 2.5 m
rg x az resolution: 9.0 m

Medium Resolution, 16 meters [16M]

pixel size: 6.25 m
rg x az resolution: 16.0 m

Medium Resolution, 30 meters [SC30]

pixel size: 12.5 m
rg x az resolution: 30.0 m

Medium Resolution, 50 meters [SC50]

pixel size: 20.0 m
rg x az resolution: 50.0 m

Low Noise [SCLN]

pixel size: 40.0 m
rg x az resolution: 100.0 m

Low Resolution, 100 meters [SC100]

pixel size: 40.0 m
rg x az resolution: 100.0 m

Ship Detection

Variable

ICEYE#

ICEYE

Pixel size and Resolution

Spotlight [SL(H)]

pixel size: 0.5 m
rg x az resolution: 1.0 m

StripMap [SM(H)]

pixel size: 2.5 m
rg x az resolution: 3.0 m

Scan [SC]

pixel size: 6.0 m
rg x az resolution: 15.0 m

SAOCOM-1#

SAOCOM-1

Detected Image (DI)
Geocoded Ellipsoid Corrected (GEC)
Geocoded Terrain Corrected (GTC)

StripMap (SM)
Single and Dual Pol

pixel size: 5.0 m
rg x az resolution: 10.0 m

StripMap (SM)
Quad Pol

pixel size: 5.0 m
rg x az resolution: 10.0 m

TOPSAR Narrow (TN)
Single and Dual Pol

pixel size: 15.0 m
rg x az resolution: 30.0 m

TOPSAR Narrow (TN)
Quad Pol

pixel size: 25.0 m
rg x az resolution: 50.0 m

TOPSAR Wide (TW)
Single and Dual Pol

pixel size: 25.0 m
rg x az resolution: 50.0 m

TOPSAR Wide (TW)
Quad Pol

pixel size: 50.0 m
rg x az resolution: 100.0 m

Warning

It has been impossible to find the recommmanded pixel size from SAOCOM products. They have been set to half the resolution (as it is usually the case)

If you have more information about this, please write an issue!

Capella#

ICEYE

Pixel size and Resolution

Spotlight [SP]

pixel size: 0.35 m
rg x az resolution: 0.5 m

StripMap [SM]

pixel size: 0.6 m
rg x az resolution: 1.0 m

Sliding Spotlight [SS]

pixel size: 0.8 m
rg x az resolution: 1.2 m

GPT graphs#

You can change the SAR GPT graphs used by setting the following environment variables:

  • EOREADER_PP_GRAPH: Environment variables for pre-processing graph path.

  • EOREADER_DSPK_GRAPH: Environment variables for despeckling graph path

Warning

For performance reasons, the Terrain Correction step is done before the Despeckle step. Indeed this step is very time-consuming and better done one time on the raw image than two times on both the raw and the despeckled image. Even if this is not the regular way of handling SAR data, this shouldn’t really affect the quality of any extraction done after that.

You can change the DEM used for the Terrain Correction step by positioning the EOREADER_SNAP_DEM_NAME environment variable. Available DEMs are:

  • ACE2_5Min

  • ACE30

  • ASTER 1sec GDEM

  • Copernicus 30m Global DEM (by default)

  • Copernicus 90m Global DEM

  • GETASSE30

  • SRTM 1Sec HGT

  • SRTM 3Sec

  • External DEM

If External DEM is set, you must specify the DEM you want by positioning the EOREADER_DEM_PATH to a DEM that can be read by SNAP.

Known SNAP bugs#

See the FAQ for known SNAP bugs.

What to know if you are changing a graph#

Those graphs should have a reader and a writer on this model:

<graph id="Graph">
 <version>1.0</version>
 <node id="Read">
  <operator>Read</operator>
  <sources/>
  <parameters class="com.bc.ceres.binding.dom.XppDomElement">
  <file>$file</file>
  </parameters>
 </node>
 <node id="Write">
  <operator>Write</operator>
  <sources>
  <sourceProduct refid="????"/>
  </sources>
  <parameters class="com.bc.ceres.binding.dom.XppDomElement">
  <file>$out</file>
  <formatName>BEAM-DIMAP</formatName>
  </parameters>
 </node>
</graph>

Warning

Pay attention to set $file and $out and leave the BEAM-DIMAP file format. The first graph must orthorectify your SAR data, but should not despeckle it. The second graph is precisely charged to do it.

SNAP graphs are run on every band separatly.

The pre-processing graph should also have a Calibration and a Terrain Correction step with the following wildcards that are set automatically in the module:

  • $calib_pola: Polarization of the band to calibrate

  • $dem_name: SNAP DEM name

  • $dem_path: DEM path (that can be use by SNAP, so only TIFF DEMs)

  • $res_m: Resolution in meters

  • $res_deg: Resolution in degrees

  • $crs: CRS

  • The nodata value should always be set to 0.

The default Calibration step is:

<node id="Calibration">
    <operator>Calibration</operator>
    <sources>
        <sourceProduct refid="ThermalNoiseRemoval"/>
    </sources>
    <parameters class="com.bc.ceres.binding.dom.XppDomElement">
        <sourceBands/>
        <auxFile>Latest Auxiliary File</auxFile>
        <externalAuxFile/>
        <outputImageInComplex>false</outputImageInComplex>
        <outputImageScaleInDb>false</outputImageScaleInDb>
        <createGammaBand>false</createGammaBand>
        <createBetaBand>false</createBetaBand>
        <selectedPolarisations>${calib_pola}</selectedPolarisations>
        <outputSigmaBand>true</outputSigmaBand>
        <outputGammaBand>false</outputGammaBand>
        <outputBetaBand>false</outputBetaBand>
    </parameters>
</node>

The default Terrain Correction step is:

<node id="Terrain-Correction">
    <operator>Terrain-Correction</operator>
    <sources>
        <sourceProduct refid="LinearToFromdB"/>
    </sources>
    <parameters class="com.bc.ceres.binding.dom.XppDomElement">
        <sourceBands/>
        <demName>${dem_name}</demName>
        <externalDEMFile>${dem_path}</externalDEMFile>
        <externalDEMNoDataValue>0.0</externalDEMNoDataValue>
        <externalDEMApplyEGM>true</externalDEMApplyEGM>
        <demResamplingMethod>BILINEAR_INTERPOLATION</demResamplingMethod>
        <imgResamplingMethod>BILINEAR_INTERPOLATION</imgResamplingMethod>
        <pixelSpacingInMeter>${res_m}</pixelSpacingInMeter>
        <pixelSpacingInDegree>${res_deg}</pixelSpacingInDegree>
        <mapProjection>${crs}</mapProjection>
        <alignToStandardGrid>false</alignToStandardGrid>
        <standardGridOriginX>0.0</standardGridOriginX>
        <standardGridOriginY>0.0</standardGridOriginY>
        <nodataValueAtSea>false</nodataValueAtSea>
        <saveDEM>false</saveDEM>
        <saveLatLon>false</saveLatLon>
        <saveIncidenceAngleFromEllipsoid>false</saveIncidenceAngleFromEllipsoid>
        <saveLocalIncidenceAngle>false</saveLocalIncidenceAngle>
        <saveProjectedLocalIncidenceAngle>false</saveProjectedLocalIncidenceAngle>
        <saveSelectedSourceBand>true</saveSelectedSourceBand>
        <applyRadiometricNormalization>false</applyRadiometricNormalization>
        <saveSigmaNought>false</saveSigmaNought>
        <saveGammaNought>false</saveGammaNought>
        <saveBetaNought>false</saveBetaNought>
        <incidenceAngleForSigma0>Use projected local incidence angle from DEM</incidenceAngleForSigma0>
        <incidenceAngleForGamma0>Use projected local incidence angle from DEM</incidenceAngleForGamma0>
        <auxFile>Latest Auxiliary File</auxFile>
        <externalAuxFile/>
    </parameters>
</node>

Default SNAP resolution#

You can override default SNAP pixel spacing (in meters) when geocoding SAR bands by setting the following environment variable:

  • EOREADER_SAR_DEFAULT_RES: 0.0 by default, which means using the product’s default pixel spacing

Documentary Sources#

Copernicus#

Sentinel-1#

RADARSAT#

COSMO-Skymed#

TerraSAR-X, TanDEM-X and PAZ SAR#

ICEYE#

SAOCOM-1#

Capella#

Documentation last accessed on the 04/12/2023