SAR data

Implemented SAR satellites

Satellites

Class

Product Types

Use archive

Sentinel-1

S1Product

SLC & GRD

Yes

COSMO-Skymed

CskProduct

DGM & SCS, (others should also be OK)

No

TerraSAR-X

TsxProduct

MGD (SSC should be OK)

No

RADARSAT-2

Rs2Product

SGF (SLC should be OK)

Yes

Warning

Satellites products that cannot be used as archived have to be extracted before use.

SAR Bands

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

You also can load despeckled bands:

DEM bands

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

  • DEM

  • SLOPE

SAR satellites can only load DEM and SLOPE bands as the sun position does not impact SAR data. The SLOPE band is computed with the gdaldem tool.

These bands need a valid worldwide DEM path positioned thanks to the environment variable EOREADER_SAR_DEFAULT_RES. 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 depends on their type. Complex data are always converted back to ground range to be used.

The product resolution is read in the metadata file if possible, so the following values are given as hints:

Sentinel-1

Sentinel-1

Single Look Complex (SLC)

Ground Range Detected (GRD)
Full Resolution (FR)

Ground Range Detected (GRD)
High Resolution (HR)

Ground Range Detected (GRD)
Medium Resolution (MR)

StripMap (SM)

1.5x3.6 m to 3.1x4.1 m

3.5m

10.0m

40.0m

Interferometric Wide swath (IW)

2.3x14.1 m

10.0m

40.0m

Extra-Wide swath (EW)

5.9x19.9 m

25.0m

40.0m

Wave (WV)

1.7x4.1 m and 2.7x4.1 m

25.0m

COSMO-Skymed

COSMO-Skymed

Single-look Complex Slant (SCS)

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

Spotlight
Mode-2 (S2)

1.1-0.9x0.91m

1.0m

StripMap
Himage (HI)

3.0-2.6x2.4-2.6m

5.0m

StripMap
PingPong (PP)

11-10x9.7m

20.0m

ScanSAR
Wide Region (WR)

13.5x23m

30.0m

ScanSAR
Huge Region (HR)

13.5x38.0m

100.0m

TerraSAR-X

TerraSAR-X

Single-look Slant Range (SSC)

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

0.9x2.0m

1.5m or 1.25m

4.0m or 3.25m

StripMap (SM)
Dual-Pol

0.9x2.5m

3.0m

5.5m or 4.5m

High Resolution Spotlight (HS)
Single-Pol

0.9x0.8m

1.5m or 0.5m

2.0m or 1.5m

High Resolution Spotlight (HS)
Dual-Pol

0.9x1.5m

1.5m or 1.0m

3.0m or 2.0m

Spotlight (SL)
Single-Pol

0.9x1.3m

1.5m or 0.75m

3.0m or 1.75m

Spotlight (SL)
Dual-Pol

0.9x2.6m

3.5m or 3.4m

8.5m or 5.5m

Staring Spotlight (ST)
Single-Pol

0.5x0.2m

0.4m or 0.2m

0.8m or 0.4m

ScanSAR (SC)
Four Beams

0.9x13m

8.25m

ScanSAR (SC)
Six Beams

1.4x?m

15.0m

RADARSAT-2

RADARSAT-2

Single-look complex (SLC)

SAR georeferenced extra(SGX)

SAR georeferenced fine (SGF)

SAR systematic geocorrected (SSG)

SAR precision geocorrected (SPG)

ScanSAR narrow beam (SCN)

ScanSAR wide beam (SCW)

ScanSAR fine (SCF)

ScanSAR sampled (SCS)

Spotlight

1.3x0.4m

1.0 or 0.8x1/3m

0.5m

0.5m

0.5m

Ultra-Fine

1.3x2.1m

1.0x1.0 or 0.8x0.8m

1.56m

1.56m

1.56m

Wide Ultra-Fine

1.3x2.1m

1.0m

1.56m

1.56m

1.56m

Multi-Look Fine

2.7x2.9m

3.13m

6.25m

6.25m

6.25m

Wide Multi-Look Fine

2.7x2.9m

3.13m

6.25m

6.25m

6.25m

Extra-Fine

Full Res: 2.7x2.9m
Fine Res: 4.3x5.8m
Full Res: 7.1x5.8m
Wide Res: 10.6x5.8m

1 look: 2.0m
4 looks: 3.13m
28 looks: 5.0m

1 look: 3.13m
4 looks: 6.25m
28 looks: 8.0m

3.13m

3.13m

Fine

4.7x5.1m

3.13m

6.25m

6.25m

6.25m

Wide-Fine

4.7x5.1m

3.13m

6.25m

6.25m

6.25m

Standard

8.0 or 11.8x5.1m

8.0m

12.5m

12.5m

12.5m

Wide

11.8x5.1m

10.0m

12.5m

12.5m

12.5m

Extended High

11.8x5.1m

8.0m

12.5m

12.5m

12.5m

Extended Low

8.0x5.1m

10.0m

12.5m

12.5m

12.5m

Fine Quad-Pol

4.7x5.1m

3.13m

3.13m

3.13m

3.13m

Wide Quad-Pol

4.7x5.1m

3.13m

3.13m

3.13m

3.13m

Standard Quad-Pol

8.0 or 11.8x5.1m

8.0x3.13m

8.0x3.13m

8.0x3.13m

8.0x3.13m

Wide Standard Quad-Pol

8.0 or 11.8x5.1m

8.0x3.13m

8.0x3.13m

8.0x3.13m

8.0x3.13m

ScanSAR Narrow

25.0m

25.0m

25.0m

ScanSAR Wide

50.0m

50.0m

50.0m

Ship (Detection of vessels)

40.0m

20.0m

Ocean Surveillance

50.0m

35.0x25.0m

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.

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.

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

- `$res_m`: Resolution in meters
- `$res_deg`: Resolution in degrees
- `$crs`: CRS
- The nodata value should **always** be set to 0.

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>GETASSE30</demName>
        <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>true</nodataValueAtSea>
        <saveDEM>false</saveDEM>
        <saveLatLon>false</saveLatLon>
        <saveIncidenceAngleFromEllipsoid>false</saveIncidenceAngleFromEllipsoid>
        <saveLocalIncidenceAngle>false</saveLocalIncidenceAngle>
        <saveProjectedLocalIncidenceAngle>false</saveProjectedLocalIncidenceAngle>
        <saveSelectedSourceBand>true</saveSelectedSourceBand>
        <outputComplex>false</outputComplex>
        <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)