SAR data#
You will find a SAR tutorial here.
Implemented SAR constellations#
Constellations |
Class |
Use archive |
|---|---|---|
|
❌ |
|
|
❌ |
|
|
❌ |
|
|
❌ |
|
|
❌ |
|
|
✅ for ground range data, ❌ for complex data |
|
|
✅ |
|
|
|
✅ for ASF |
|
❌ |
|
|
❌ |
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 |
|---|---|---|
|
SLC |
✅ |
|
GEC |
✅ |
|
GEO |
✅ |
|
SICD, SIDD, CPHD |
❌ |
|
SCS |
✅ |
|
DGM |
✅ |
|
DGM |
⚠ |
|
GEC, GTC |
⚠ |
|
SLC |
✅ |
|
GRD |
✅ |
|
ORTHO |
💤 |
|
SLC |
⚠ |
|
GRC, GCC, GCD |
⚠ |
|
GRD |
✅ |
|
SLC |
✅ |
|
SGF, SGX, SSG |
✅ |
|
SCN, SCF, SCW, SCS, SPG |
⚠ |
|
SLC |
✅ |
|
GRD |
✅ |
|
✅ |
|
|
SLC |
✅ |
|
ID |
⚠ |
|
GEC |
✅ |
|
GTC |
✅ |
|
SSC |
✅ |
|
MGD |
✅ |
|
GEC |
⚠ |
|
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):
Sentinel-1 COGS provided by the Copernicus Dataspace are handled if you are using SNAP 10 or higher.
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
Intensitybands are used (not theI,Qfor complex data orAmplitudefor 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 keywordSAR_INTERP_NAto True when loading or stacking SAR data
According to what contains the products, allowed SAR bands are:
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
DEMSLOPE
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 recommended 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) |
Ground Range Detected (GRD) |
Ground Range Detected (GRD) |
|---|---|---|---|
StripMap (SM) |
pixel size: 3.5 m |
pixel size: 10.0 m |
pixel size: 40.0 m |
Interferometric Wide swath (IW) |
pixel size: 10.0 m |
pixel size: 40.0 m |
|
Extra-Wide swath (EW) |
pixel size: 25.0 m |
pixel size: 40.0 m |
|
Wave (WV) |
pixel size: 25.0 m |
COSMO-Skymed 1st Generation#
COSMO-Skymed |
Detected Ground Multi-look (DGM) |
|---|---|
Spotlight |
pixel size: 0.5 m |
StripMap |
pixel size: 2.5 m |
StripMap |
pixel size: 2.5 m |
StripMap |
pixel size: 10.0 m |
ScanSAR |
pixel size: 15.0 m |
ScanSAR |
pixel size: 50.0 m |
COSMO-Skymed 2nd Generation#
COSMO-Skymed |
Detected Ground Multi-look (DGM) |
|---|---|
SPOTLIGHT 2A |
Multilook ID: #1: pixel size: 0.15 m, rg x az resolution: 0.4 m |
SPOTLIGHT 2B |
Multilook ID: #1: pixel size: 0.25 m, rg x az resolution: 0.7 m |
SPOTLIGHT 2C |
Multilook ID: #1: pixel size: 0.3 m, rg x az resolution: 0.8 m |
STRIPMAP & QUADPOL |
Multilook ID: #1: pixel size: 1.25 m, rg x az resolution: 3.0 m |
SCANSAR1 |
Multilook ID: #1: pixel size: 5.0 m, rg x az resolution: 20.0 m |
SCANSAR2 |
Multilook ID: #1: pixel size: 10.0 m, rg x az resolution: 40.0 m |
PINGPONG |
Multilook ID: #1: pixel size: 2.0 m, rg x az resolution: 12.0 m |
TerraSAR-X & TanDEM-X & PAZ SAR#
TerraSAR-X |
Multi Look Ground Range (MGD) |
|---|---|
StripMap (SM) |
pixel size: 1.25 m |
StripMap (SM) |
pixel size: 3.0 m |
High Resolution Spotlight (HS) |
pixel size: 0.5 m |
High Resolution Spotlight (HS) |
pixel size: 1.0 m |
Spotlight (SL) |
pixel size: 0.75 m |
Spotlight (SL) |
pixel size: 1.0 m |
Staring Spotlight (ST) |
pixel size: 0.2 m |
ScanSAR (SC) |
pixel size: 8.25 m |
ScanSAR (SC) |
pixel size: 15.0 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) |
|---|---|---|---|
Spotlight |
pixel size: 0.8 m (1.0 if incidence angle < 48°) |
pixel size: 0.5 m |
pixel size: 0.5 m |
Ultra-Fine |
pixel size: 0.8 m (1.0 if incidence angle < 48°) |
pixel size: 1.5625 m |
pixel size: 1.5625 m |
Multi-Look Fine |
pixel size: 3.125 m |
pixel size: 6.25 m |
pixel size: 6.25 m |
Extra-Fine /* |
pixel size: 2.0 m |
pixel size: 3.125 m |
pixel size: 3.125 m |
Fine |
pixel size: 3.125 m |
pixel size: 6.25 m |
pixel size: 6.25 m |
Standard |
pixel size: 8.0 m |
pixel size: 12.5 m |
pixel size: 12.5 m |
Extended High |
pixel size: 8.0 m |
pixel size: 12.5 m |
pixel size: 12.5 m |
Extended Low |
pixel size: 10.0 m |
pixel size: 12.5 m |
pixel size: 12.5 m |
Fine Quad-Pol |
pixel size: 3.125 m |
pixel size: 3.125 m |
|
Standard Quad-Pol |
pixel size: 8.0 m |
pixel size: 8.0 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 Narrow |
pixel size: 25.0 m |
pixel size: 25.0 m |
|
ScanSAR Wide |
pixel size: 50.0 m |
pixel size: 50.0 m |
Other modes#
RADARSAT-2 |
From SLC |
Other product types |
|---|---|---|
Ship (Detection of vessels) |
pixel size: 20.0 m |
pixel size: 40.0 m |
Ocean Surveillance |
pixel size: 35.0 m |
pixel size: 50.0 m |
RADARSAT-Constellation#
RADARSAT-Constellation |
Pixel size and Resolution |
|---|---|
Spotlight [FSL] |
pixel size: 0.33 m |
Very-High Resolution, 3 meters [3M] |
pixel size: 1.25 m |
High Resolution, 5 meters [5M] |
pixel size: 2.0 m |
Quad-Polarization [QP] |
pixel size: 2.5 m |
Medium Resolution, 16 meters [16M] |
pixel size: 6.25 m |
Medium Resolution, 30 meters [SC30] |
pixel size: 12.5 m |
Medium Resolution, 50 meters [SC50] |
pixel size: 20.0 m |
Low Noise [SCLN] |
pixel size: 40.0 m |
Low Resolution, 100 meters [SC100] |
pixel size: 40.0 m |
Ship Detection |
Variable |
ICEYE#
ICEYE |
Pixel size and Resolution |
|---|---|
Spotlight [SL(H)] |
pixel size: 0.5 m |
StripMap [SM(H)] |
pixel size: 2.5 m |
Scan [SC] |
pixel size: 6.0 m |
SAOCOM-1#
SAOCOM-1 |
Detected Image (DI) |
|---|---|
StripMap (SM) |
pixel size: 5.0 m |
StripMap (SM) |
pixel size: 5.0 m |
TOPSAR Narrow (TN) |
pixel size: 15.0 m |
TOPSAR Narrow (TN) |
pixel size: 25.0 m |
TOPSAR Wide (TW) |
pixel size: 25.0 m |
TOPSAR Wide (TW) |
pixel size: 50.0 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#
Capella |
Pixel size and Resolution |
|---|---|
Spotlight [SP] |
pixel size: 0.35 m |
Sliding Spotlight [SS] |
pixel size: 0.6 m |
StripMap [SM] |
pixel size: 0.8 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_5MinACE30ASTER 1sec GDEMCopernicus 30m Global DEM(by default)Copernicus 90m Global DEMGETASSE30SRTM 1Sec HGTSRTM 3SecExternal 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 separately.
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: CRSThe 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