SAR data#

You will find a SAR tutorial here.

Implemented SAR constellations#

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

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

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:

  • VV_DSPK

  • VH_DSPK

  • HH_DSPK

  • HV_DSPK

  • RH_DSPK (only for RADARSAT-Constellation)

  • RV_DSPK (only for RADARSAT-Constellation)

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 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.

SAR default resolution is the pixel spacing given by the constellation provider, to follow common habits. Sometimes, especially when converting complex data to ground range, this resolution needs to be adaptated.

⚠ 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 resolution when loading SAR data.

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 spacing: 3.5m
rg x az resolution: 9.0m

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

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

Interferometric Wide swath (IW)

20.0m

pixel spacing: 40.0m
rg x az resolution: 88.0x87.0m

Extra-Wide swath (EW)

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

pixel spacing: 40.0m
rg x az resolution: 93.0x87.0m

Wave (WV) *

pixel spacing: 25.0m
rg x az resolution: 52.0x51.0m

* Resolutions not provided in the Data Access Portfolio. Available here.

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)

1.0m

StripMap
Himage from SCS (HI)

3.0m

StripMap
Himage GRD (HI)

5.0m

StripMap
PingPong (PP)

20.0m

ScanSAR
Wide Region (WR)

30.0m

ScanSAR
Huge Region (HR)

100.0m

COSMO-Skymed 2nd Generation#

Resolutions not provided in the Data Access Portfolio. Available here.

COSMO-Skymed
2nd Generation

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

SPOTLIGHT_2_A

~0.4m

SPOTLIGHT_2_B

~0.63m

SPOTLIGHT-2_C

~0.8m

STRIPMAP & QUADPOL

~3.0m

SCANSAR1

~20.0m

SCANSAR2

~40.0m

PINGPONG

~12.0m

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
(high resolution, SE)

Multi Look Ground Range (MGD)
Geocoded Ellipsoid Corrected (GEC)
Enhanced Ellipsoid Corrected (EEC)
Radiometrically enhanced
(high radiometry, RE)

StripMap (SM)
Single-Pol

3.3m

7.0m *

StripMap (SM)
Dual-Pol

6.6m

9.9m *

High Resolution Spotlight (HS)
Single-Pol

1.1m

3.0m *

High Resolution Spotlight (HS)
Dual-Pol

2.2m

4.4m *

Spotlight (SL)
Single-Pol

1.7m

3.8m *

Spotlight (SL)
Dual-Pol

3.4m

5.5m *

Staring Spotlight (ST)
Single-Pol

0.24m

0.9m *

ScanSAR (SC)
Four Beams

18.5m

ScanSAR (SC)
Six Beams

40.0m

* Resolutions not provided in the Data Access Portfolio. Available here.

RADARSAT-2#

RADARSAT-2

Maximal spatial resolution

Spotlight

1.0m

Ultra-Fine

3.0m

Wide Ultra-Fine

3.0m

Multi-Look Fine

5.0m

Wide Multi-Look Fine

5.0m

Extra-Fine

5.0m

Fine

8.0m

Wide-Fine

8.0m

Standard

25.0m

Wide

25.0m

Extended High

25.0m

Extended Low

25.0m

Fine Quad-Pol

12.0m

Wide Quad-Pol

12.0m

Standard Quad-Pol

25.0m

Wide Standard Quad-Pol

25.0m

ScanSAR Narrow

60.0m

ScanSAR Wide

100.0m

Ship (Detection of vessels)

35.0m

Ocean Surveillance

50.0m

RADARSAT-Constellation#

Resolutions not provided in the Data Access Portfolio. Available here.

RADARSAT-Constellation

Resolution

Spotlight [FSL]

1.0m

Very-High Resolution, 3 meters [3M]

3.0m

High Resolution, 5 meters [5M]

5.0m

Quad-Polarization [QP]

9.0m

Medium Resolution, 16 meters [16M]

16.0m

Medium Resolution, 30 meters [SC30]

30.0m

Medium Resolution, 50 meters [SC50]

50.0m

Low Noise [SCLN]

100.0m

Low Resolution, 100 meters [SC100]

100.0m

Ship Detection

Variable

ICEYE#

Resolutions not provided in the Data Access Portfolio. Available here.

ICEYE

Resolution

Spotlight [SL(H)]

1.0m

StripMap [SM(H)]

3.0m

Scan [SC]

< 15.0m

SAOCOM-1#

Resolutions not provided in the Data Access Portfolio. Available here.

SAOCOM-1

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

StripMap (SM)
Single and Dual Pol

10.0m

StripMap (SM)
Quad Pol

10.0m

TOPSAR Narrow (TN)
Single and Dual Pol

30.0m

TOPSAR Narrow (TN)
Quad Pol

50.0m

TOPSAR Wide (TW)
Single and Dual Pol

50.0m

TOPSAR Wide (TW)
Quad Pol

100.0m

Capella#

Resolutions not provided in the Data Access Portfolio. Available here.

ICEYE

Resolution

Spotlight [SP]

0.35m

StripMap [SM]

0.8m

Sliding Spotlight [SS]

0.6m

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.

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 resolution (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 resolution

Documentary Sources#

Copernicus#

Sentinel-1#

RADARSAT#

COSMO-Skymed#

TerraSAR-X, TanDEM-X and PAZ SAR#

ICEYE#

SAOCOM-1#

Capella#

Documentation last accessed on the 02/12/2022