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SAR Extension Specification

This document explains the fields of the Synthetic-Aperture Radar (SAR) Extension to the SpatioTemporal Asset Catalog (STAC) specification.

SAR data is considered to be data that represents a snapshot of the earth for a single date and time taken by a synthetic-aperture radar system such as Sentinel-1, RADARSAT or EnviSAT.

If the data has been collected by a satellite, it is recommended to use the Satellite extension. If the data has been collected on an airborne platform it is recommended to use the Instrument Fields.

To describe frame start and end times, use the Date and Time Range fields.

To describe the product type, use the Product extension.

Fields

The fields in the table below can be used in these parts of STAC documents:

  • Catalogs
  • Collections
  • Item Properties (incl. Summaries in Collections)
  • Assets (for both Collections and Items, incl. Item Asset Definitions in Collections)
  • Links

Important

In this specification range values are meant to be measured perpendicular to the flight path and azimuth values are meant to be measured parallel to the flight path.

Field NameTypeDescription
sar:polarizations[string]RECOMMENDED. Any combination of polarizations.
sar:frequency_bandstringRECOMMENDED. The common name for the frequency band to make it easier to search for bands across instruments. See section "Common Frequency Band Names" for a list of accepted names.
sar:center_frequencynumberRECOMMENDED. The center frequency of the radar signal transmitted by the instrument, in gigahertz (GHz).
sar:bandwidthnumberThe range bandwidth of the SAR instrument, in gigahertz (GHz), representing the full bandwidth used in range compression and image formation.
sar:resolution_rangenumberThe range resolution, which is the maximum ability to distinguish two adjacent targets perpendicular to the flight path, in meters (m).
sar:resolution_azimuthnumberThe azimuth resolution, which is the maximum ability to distinguish two adjacent targets parallel to the flight path, in meters (m).
sar:pixel_spacing_rangenumberThe range pixel spacing, which is the distance between adjacent pixels perpendicular to the flight path, in meters (m). Strongly RECOMMENDED to be specified for products of type GRD.
sar:pixel_spacing_azimuthnumberThe azimuth pixel spacing, which is the distance between adjacent pixels parallel to the flight path, in meters (m). Strongly RECOMMENDED to be specified for products of type GRD.
sar:looks_rangenumberNumber of range looks, which is the number of groups of signal samples (looks) perpendicular to the flight path.
sar:looks_azimuthnumberNumber of azimuth looks, which is the number of groups of signal samples (looks) parallel to the flight path.
sar:looks_equivalent_numbernumberThe equivalent number of looks (ENL).
sar:observation_directionstringAntenna pointing direction relative to the flight trajectory of the satellite, either left or right.
sar:relative_burstnumberIdentification number that uniquely identifies a burst cycle within each repeat cycle.
sar:beam_ids[string]Composition of the swath of the SAR acquision referencing the beam identifiers.
sar:product_typestringDEPRECATED in favor of product:type. See Product type.
sar:instrument_modestringDEPRECATED in favor of instrument_modes.

Caution

  • v1.0 of the extension did require sar:product_type.
  • v1.1 deprecates sar:product_type and it's not required any longer, but product:type is strongly recommended.
  • v2.0 is going to remove sar:product_type.
  • v1.0 of the extension did recommend sar:instrument_mode.
  • v1.3.2 deprecates sar:instrument_mode, but instrument_modes is strongly recommended.
  • v2.0 is going to remove sar:instrument_mode.

Additional Field Information

sar:polarizations

Specifies a single polarization or a polarization combination. Allowed values: HH, VV, HV, VH, LH, LV, RH, RV, CH or CV For single polarized radars, one the allowed values must be set. For dual polarized radars and alternating polarization, add the corresponding polarizations to the array. For fully polarimetric radars, add all polarizations to the array. For instance, for HH+HV, add both HH and HV.

Important

In Item Properties and Collections, sar:polarizations must be a set with unique elements. In assets sar:polarizations can contain duplicate elements and, if possible, the polarizations must appear in the same order as in the file.

sar:beam_ids

The sar:beam_ids field is used to reference the beam identifiers of the SAR acquisition. According to the mission and the sensor mode, the beam identifiers can be used to identify the composition of the swath of the SAR acquisition. The beam identifiers are usually provided in the metadata of the SAR data.

sar:frequency_band - Common Frequency Band Names

The sar:frequency_band is the name that is commonly used to refer to that band's spectral properties. The table below shows the common name based on the wavelength and frequency ranges for several SAR satellites.

Common NameWavelength Range (cm)Frequency Range (GHz)Satellites
P30 - 1200.25 - 1
L15 - 301 - 2ALOS, JERS, NISAR, SOACOM
S7.5 - 152 - 4HJ-1C
C3.8 - 7.54 - 8EnviSat, ERS, Radarsat, Risat-1, Sentinel-1
X2.4 - 3.88 - 12.5Cosmo-SkyMed, TerraSAR-X, TanDEM-X, PAZ, KOMPSat-5
Ku1.7 - 2.412.5 - 18
K1.1 - 1.718 - 26.5
Ka0.75 - 1.126.5 - 40

Product type

It is RECOMMENDED to include the product:type field. The product type for SAR data defines the type of processed data contained in the assets. A list of suggestions for product:type include:

product:typeTypeDescription
SSCcomplexSingle-look Slant-range Complex image (standard SLC)
MGDamplitudeMultilooked Ground-range Detected image
GRDamplitudeMultilooked Ground-range Detected image (used by Sentinel-1)
GECamplitudeGeocoded Ellipsoid Corrected image
GTCamplitudeGeocoded Terrain Corrected image
RTCamplitudeGeocoded Radiometrically Terrain Corrected image
SGCcomplexSingle-look Ground projected Complex image
SLCcomplexSingle-look Ground projected Complex image (used by Sentinel-1)

This can vary by data provider, who all may use slightly different names. Sentinel-1 for instance uses GRD, which is the same as the more general MGD and SLC instead of SGC.

Date and Time

In SAR, you usually have frame start and end time. To describe this information it is recommended to use the Date and Time Range fields. The center time of the frame should be specified with the datetime property for STAC Items.

Best Practices

One of the emerging best practices is to use Asset Roles to provide clients with more information about the assets in an item. The following list includes a shared vocabulary for some common SAR assets. This list should not be considered definitive, and implementors are welcome to use other asset roles. If consensus and tooling consolidates around these role names then they will be specified in the future as more standard than just 'best practices'.

Role NameDescription
local-incidence-anglePoints to the local incidence angle file.
ellipsoid-incidence-anglePoints to the ellipsoid incidence angle file.
noise-powerPoints to the noise power file.
amplitudePoints to the intensity file with focused SAR data that has been ground range detected (e.g. GRD).
magnitudePoints to the intensity file where data are represented as complex numbers containing amplitude and phase information (e.g SLC).
sigma0Points to the radar backscatter file where data is referenced in ground surface. It is often derived from an amplitude or a magnitude role asset.
beta0Points to the radar backscatter file where data is referenced in the slant range plane and is radiometrically calibrated. It is often derived from an amplitude or a magnitude role asset.
gamma0Points to the radar backscatter file where data is referenced in the plane perpendicular to the line of sight. It is often derived from an amplitude or a magnitude role asset.
date-offsetPoints to the date-offset file.
covmatPoints to the Points to the Normalized Polarimetric Radar Covariance Matrix (CovMat) file.
prdPoints to the Polarimetric Radar Decomposition (PRD) file.

Contributing

All contributions are subject to the STAC Specification Code of Conduct. For contributions, please follow the STAC specification contributing guide Instructions for running tests are copied here for convenience.

Running tests

The same checks that run as checks on PR's are part of the repository and can be run locally to verify that changes are valid. To run tests locally, you'll need npm, which is a standard part of any node.js installation.

First you'll need to install everything with npm once. Just navigate to the root of this repository and on your command line run:

npm install

Then to check markdown formatting and test the examples against the JSON schema, you can run:

npm test

This will spit out the same texts that you see online, and you can then go and fix your markdown or examples.

If the tests reveal formatting problems with the examples, you can fix them with:

npm run format-examples

About

Covers synthetic-aperture radar data that represents a snapshot of the earth for a single date and time.

Resources

Readme
Apache-2.0 license
Activity
Custom properties

Stars

22 stars

Watchers

6 watching

Forks

10 forks
Report repository

Releases

Packages

Used by

Contributors

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GitHub - stac-extensions/sar: Covers synthetic-aperture radar data that represents a snapshot of the earth for a single date and time. · GitHub
Skip to content
BranchesTags
Repository files navigation
SAR Extension Specification
This document explains the fields of the Synthetic-Aperture Radar (SAR) Extension to the
SpatioTemporal Asset Catalog (STAC) specification.
SAR data is considered to be data that represents a snapshot of the earth for a single date and time taken by a synthetic-aperture radar system
such as Sentinel-1, RADARSAT or EnviSAT.
If the data has been collected by a satellite, it is recommended to use the
Satellite extension.
If the data has been collected on an airborne platform it is recommended to use the
Instrument Fields.
To describe frame start and end times, use the
Date and Time Range fields.
To describe the product type, use the Product extension.
Fields
The fields in the table below can be used in these parts of STAC documents:
  •  Catalogs
  •  Collections
  •  Item Properties (incl. Summaries in Collections)
  •  Assets (for both Collections and Items, incl. Item Asset Definitions in Collections)
  •  Links
Important
In this specification range values are meant to be measured perpendicular to the flight path
and azimuth values are meant to be measured parallel to the flight path.
Field NameTypeDescription
sar:polarizations[string]RECOMMENDED. Any combination of polarizations.
sar:frequency_bandstringRECOMMENDED. The common name for the frequency band to make it easier to search for bands across instruments. See section "Common Frequency Band Names" for a list of accepted names.
sar:center_frequencynumberRECOMMENDED. The center frequency of the radar signal transmitted by the instrument, in gigahertz (GHz).
sar:bandwidthnumberThe range bandwidth of the SAR instrument, in gigahertz (GHz), representing the full bandwidth used in range compression and image formation.
sar:resolution_rangenumberThe range resolution, which is the maximum ability to distinguish two adjacent targets perpendicular to the flight path, in meters (m).
sar:resolution_azimuthnumberThe azimuth resolution, which is the maximum ability to distinguish two adjacent targets parallel to the flight path, in meters (m).
sar:pixel_spacing_rangenumberThe range pixel spacing, which is the distance between adjacent pixels perpendicular to the flight path, in meters (m). Strongly RECOMMENDED to be specified for products of type GRD.
sar:pixel_spacing_azimuthnumberThe azimuth pixel spacing, which is the distance between adjacent pixels parallel to the flight path, in meters (m). Strongly RECOMMENDED to be specified for products of type GRD.
sar:looks_rangenumberNumber of range looks, which is the number of groups of signal samples (looks) perpendicular to the flight path.
sar:looks_azimuthnumberNumber of azimuth looks, which is the number of groups of signal samples (looks) parallel to the flight path.
sar:looks_equivalent_numbernumberThe equivalent number of looks (ENL).
sar:observation_directionstringAntenna pointing direction relative to the flight trajectory of the satellite, either left or right.
sar:relative_burstnumberIdentification number that uniquely identifies a burst cycle within each repeat cycle.
sar:beam_ids[string]Composition of the swath of the SAR acquision referencing the beam identifiers.
sar:product_typestringDEPRECATED in favor of product:type. See Product type.
sar:instrument_modestringDEPRECATED in favor of instrument_modes.
Caution
  • v1.0 of the extension did require sar:product_type.
  • v1.1 deprecates sar:product_type and it's not required any longer, but
product:type is strongly recommended.
  • v2.0 is going to remove sar:product_type.
  • v1.0 of the extension did recommend sar:instrument_mode.
  • v1.3.2 deprecates sar:instrument_mode, but
instrument_modes is strongly recommended.
  • v2.0 is going to remove sar:instrument_mode.
Additional Field Information
sar:polarizations
Specifies a single polarization or a polarization combination.
Allowed values: HH, VV, HV, VH, LH, LV, RH, RV, CH or CV
For single polarized radars, one the allowed values must be set.
For dual polarized radars and alternating polarization, add the corresponding polarizations to the array.
For fully polarimetric radars, add all polarizations to the array.
For instance, for HH+HV, add both HH and HV.
Important
In Item Properties and Collections, sar:polarizations must be a set with unique elements.
In assets sar:polarizations can contain duplicate elements and, if possible, the polarizations must appear in the same order as in the file.
sar:beam_ids
The sar:beam_ids field is used to reference the beam identifiers of the SAR acquisition. According to the mission and the sensor mode,
the beam identifiers can be used to identify the composition of the swath of the SAR acquisition.
The beam identifiers are usually provided in the metadata of the SAR data.
sar:frequency_band - Common Frequency Band Names
The sar:frequency_band is the name that is commonly used to refer to that band's spectral
properties. The table below shows the common name based on the wavelength and frequency ranges for several SAR satellites.
Common NameWavelength Range (cm)Frequency Range (GHz)Satellites
P30 - 1200.25 - 1
L15 - 301 - 2ALOS, JERS, NISAR, SOACOM
S7.5 - 152 - 4HJ-1C
C3.8 - 7.54 - 8EnviSat, ERS, Radarsat, Risat-1, Sentinel-1
X2.4 - 3.88 - 12.5Cosmo-SkyMed, TerraSAR-X, TanDEM-X, PAZ, KOMPSat-5
Ku1.7 - 2.412.5 - 18
K1.1 - 1.718 - 26.5
Ka0.75 - 1.126.5 - 40
Product type
It is RECOMMENDED to include the product:type field.
The product type for SAR data defines the type of processed data contained in the assets.
A list of suggestions for product:type include:
product:typeTypeDescription
SSCcomplexSingle-look Slant-range Complex image (standard SLC)
MGDamplitudeMultilooked Ground-range Detected image
GRDamplitudeMultilooked Ground-range Detected image (used by Sentinel-1)
GECamplitudeGeocoded Ellipsoid Corrected image
GTCamplitudeGeocoded Terrain Corrected image
RTCamplitudeGeocoded Radiometrically Terrain Corrected image
SGCcomplexSingle-look Ground projected Complex image
SLCcomplexSingle-look Ground projected Complex image (used by Sentinel-1)
This can vary by data provider, who all may use slightly different names.
Sentinel-1 for instance uses GRD, which is the same as the more general MGD and SLC instead of SGC.
Date and Time
In SAR, you usually have frame start and end time. To describe this information it is recommended to use the Date and Time Range fields.
The center time of the frame should be specified with the datetime property for STAC Items.
Best Practices
One of the emerging best practices is to use Asset Roles
to provide clients with more information about the assets in an item. The following list includes a shared vocabulary for some common SAR assets.
This list should not be considered definitive, and implementors are welcome to use other asset roles. If consensus and tooling consolidates around
these role names then they will be specified in the future as more standard than just 'best practices'.
Role NameDescription
local-incidence-anglePoints to the local incidence angle file.
ellipsoid-incidence-anglePoints to the ellipsoid incidence angle file.
noise-powerPoints to the noise power file.
amplitudePoints to the intensity file with focused SAR data that has been ground range detected (e.g. GRD).
magnitudePoints to the intensity file where data are represented as complex numbers containing amplitude and phase information (e.g SLC).
sigma0Points to the radar backscatter file where data is referenced in ground surface. It is often derived from an amplitude or a magnitude role asset.
beta0Points to the radar backscatter file where data is referenced in the slant range plane and is radiometrically calibrated. It is often derived from an amplitude or a magnitude role asset.
gamma0Points to the radar backscatter file where data is referenced in the plane perpendicular to the line of sight. It is often derived from an amplitude or a magnitude role asset.
date-offsetPoints to the date-offset file.
covmatPoints to the Points to the Normalized Polarimetric Radar Covariance Matrix (CovMat) file.
prdPoints to the Polarimetric Radar Decomposition (PRD) file.
Contributing
All contributions are subject to the
STAC Specification Code of Conduct.
For contributions, please follow the
STAC specification contributing guide Instructions
for running tests are copied here for convenience.
Running tests
The same checks that run as checks on PR's are part of the repository and can be run locally to verify that changes are valid.
To run tests locally, you'll need npm, which is a standard part of any node.js installation.
First you'll need to install everything with npm once. Just navigate to the root of this repository and on
your command line run:
npm install
Then to check markdown formatting and test the examples against the JSON schema, you can run:
npm test
This will spit out the same texts that you see online, and you can then go and fix your markdown or examples.
If the tests reveal formatting problems with the examples, you can fix them with:
npm run format-examples
About
Covers synthetic-aperture radar data that represents a snapshot of the earth for a single date and time.
Resources
Readme
Apache-2.0 license
Activity
Custom properties
Stars
22 stars
Watchers
6 watching
Forks
10 forks
Report repository
Releases
Packages
Used by
Contributors
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GitHub - stac-extensions/sar: Covers synthetic-aperture radar data that represents a snapshot of the earth for a single date and time. · GitHub
Skip to content
BranchesTags
Repository files navigation
SAR Extension Specification
This document explains the fields of the Synthetic-Aperture Radar (SAR) Extension to the
SpatioTemporal Asset Catalog (STAC) specification.
SAR data is considered to be data that represents a snapshot of the earth for a single date and time taken by a synthetic-aperture radar system
such as Sentinel-1, RADARSAT or EnviSAT.
If the data has been collected by a satellite, it is recommended to use the
Satellite extension.
If the data has been collected on an airborne platform it is recommended to use the
Instrument Fields.
To describe frame start and end times, use the
Date and Time Range fields.
To describe the product type, use the Product extension.
Fields
The fields in the table below can be used in these parts of STAC documents:
  •  Catalogs
  •  Collections
  •  Item Properties (incl. Summaries in Collections)
  •  Assets (for both Collections and Items, incl. Item Asset Definitions in Collections)
  •  Links
Important
In this specification range values are meant to be measured perpendicular to the flight path
and azimuth values are meant to be measured parallel to the flight path.
Field NameTypeDescription
sar:polarizations[string]RECOMMENDED. Any combination of polarizations.
sar:frequency_bandstringRECOMMENDED. The common name for the frequency band to make it easier to search for bands across instruments. See section "Common Frequency Band Names" for a list of accepted names.
sar:center_frequencynumberRECOMMENDED. The center frequency of the radar signal transmitted by the instrument, in gigahertz (GHz).
sar:bandwidthnumberThe range bandwidth of the SAR instrument, in gigahertz (GHz), representing the full bandwidth used in range compression and image formation.
sar:resolution_rangenumberThe range resolution, which is the maximum ability to distinguish two adjacent targets perpendicular to the flight path, in meters (m).
sar:resolution_azimuthnumberThe azimuth resolution, which is the maximum ability to distinguish two adjacent targets parallel to the flight path, in meters (m).
sar:pixel_spacing_rangenumberThe range pixel spacing, which is the distance between adjacent pixels perpendicular to the flight path, in meters (m). Strongly RECOMMENDED to be specified for products of type GRD.
sar:pixel_spacing_azimuthnumberThe azimuth pixel spacing, which is the distance between adjacent pixels parallel to the flight path, in meters (m). Strongly RECOMMENDED to be specified for products of type GRD.
sar:looks_rangenumberNumber of range looks, which is the number of groups of signal samples (looks) perpendicular to the flight path.
sar:looks_azimuthnumberNumber of azimuth looks, which is the number of groups of signal samples (looks) parallel to the flight path.
sar:looks_equivalent_numbernumberThe equivalent number of looks (ENL).
sar:observation_directionstringAntenna pointing direction relative to the flight trajectory of the satellite, either left or right.
sar:relative_burstnumberIdentification number that uniquely identifies a burst cycle within each repeat cycle.
sar:beam_ids[string]Composition of the swath of the SAR acquision referencing the beam identifiers.
sar:product_typestringDEPRECATED in favor of product:type. See Product type.
sar:instrument_modestringDEPRECATED in favor of instrument_modes.
Caution
  • v1.0 of the extension did require sar:product_type.
  • v1.1 deprecates sar:product_type and it's not required any longer, but
product:type is strongly recommended.
  • v2.0 is going to remove sar:product_type.
  • v1.0 of the extension did recommend sar:instrument_mode.
  • v1.3.2 deprecates sar:instrument_mode, but
instrument_modes is strongly recommended.
  • v2.0 is going to remove sar:instrument_mode.
Additional Field Information
sar:polarizations
Specifies a single polarization or a polarization combination.
Allowed values: HH, VV, HV, VH, LH, LV, RH, RV, CH or CV
For single polarized radars, one the allowed values must be set.
For dual polarized radars and alternating polarization, add the corresponding polarizations to the array.
For fully polarimetric radars, add all polarizations to the array.
For instance, for HH+HV, add both HH and HV.
Important
In Item Properties and Collections, sar:polarizations must be a set with unique elements.
In assets sar:polarizations can contain duplicate elements and, if possible, the polarizations must appear in the same order as in the file.
sar:beam_ids
The sar:beam_ids field is used to reference the beam identifiers of the SAR acquisition. According to the mission and the sensor mode,
the beam identifiers can be used to identify the composition of the swath of the SAR acquisition.
The beam identifiers are usually provided in the metadata of the SAR data.
sar:frequency_band - Common Frequency Band Names
The sar:frequency_band is the name that is commonly used to refer to that band's spectral
properties. The table below shows the common name based on the wavelength and frequency ranges for several SAR satellites.
Common NameWavelength Range (cm)Frequency Range (GHz)Satellites
P30 - 1200.25 - 1
L15 - 301 - 2ALOS, JERS, NISAR, SOACOM
S7.5 - 152 - 4HJ-1C
C3.8 - 7.54 - 8EnviSat, ERS, Radarsat, Risat-1, Sentinel-1
X2.4 - 3.88 - 12.5Cosmo-SkyMed, TerraSAR-X, TanDEM-X, PAZ, KOMPSat-5
Ku1.7 - 2.412.5 - 18
K1.1 - 1.718 - 26.5
Ka0.75 - 1.126.5 - 40
Product type
It is RECOMMENDED to include the product:type field.
The product type for SAR data defines the type of processed data contained in the assets.
A list of suggestions for product:type include:
product:typeTypeDescription
SSCcomplexSingle-look Slant-range Complex image (standard SLC)
MGDamplitudeMultilooked Ground-range Detected image
GRDamplitudeMultilooked Ground-range Detected image (used by Sentinel-1)
GECamplitudeGeocoded Ellipsoid Corrected image
GTCamplitudeGeocoded Terrain Corrected image
RTCamplitudeGeocoded Radiometrically Terrain Corrected image
SGCcomplexSingle-look Ground projected Complex image
SLCcomplexSingle-look Ground projected Complex image (used by Sentinel-1)
This can vary by data provider, who all may use slightly different names.
Sentinel-1 for instance uses GRD, which is the same as the more general MGD and SLC instead of SGC.
Date and Time
In SAR, you usually have frame start and end time. To describe this information it is recommended to use the Date and Time Range fields.
The center time of the frame should be specified with the datetime property for STAC Items.
Best Practices
One of the emerging best practices is to use Asset Roles
to provide clients with more information about the assets in an item. The following list includes a shared vocabulary for some common SAR assets.
This list should not be considered definitive, and implementors are welcome to use other asset roles. If consensus and tooling consolidates around
these role names then they will be specified in the future as more standard than just 'best practices'.
Role NameDescription
local-incidence-anglePoints to the local incidence angle file.
ellipsoid-incidence-anglePoints to the ellipsoid incidence angle file.
noise-powerPoints to the noise power file.
amplitudePoints to the intensity file with focused SAR data that has been ground range detected (e.g. GRD).
magnitudePoints to the intensity file where data are represented as complex numbers containing amplitude and phase information (e.g SLC).
sigma0Points to the radar backscatter file where data is referenced in ground surface. It is often derived from an amplitude or a magnitude role asset.
beta0Points to the radar backscatter file where data is referenced in the slant range plane and is radiometrically calibrated. It is often derived from an amplitude or a magnitude role asset.
gamma0Points to the radar backscatter file where data is referenced in the plane perpendicular to the line of sight. It is often derived from an amplitude or a magnitude role asset.
date-offsetPoints to the date-offset file.
covmatPoints to the Points to the Normalized Polarimetric Radar Covariance Matrix (CovMat) file.
prdPoints to the Polarimetric Radar Decomposition (PRD) file.
Contributing
All contributions are subject to the
STAC Specification Code of Conduct.
For contributions, please follow the
STAC specification contributing guide Instructions
for running tests are copied here for convenience.
Running tests
The same checks that run as checks on PR's are part of the repository and can be run locally to verify that changes are valid.
To run tests locally, you'll need npm, which is a standard part of any node.js installation.
First you'll need to install everything with npm once. Just navigate to the root of this repository and on
your command line run:
npm install
Then to check markdown formatting and test the examples against the JSON schema, you can run:
npm test
This will spit out the same texts that you see online, and you can then go and fix your markdown or examples.
If the tests reveal formatting problems with the examples, you can fix them with:
npm run format-examples
About
Covers synthetic-aperture radar data that represents a snapshot of the earth for a single date and time.
Resources
Readme
Apache-2.0 license
Activity
Custom properties
Stars
22 stars
Watchers
6 watching
Forks
10 forks
Report repository
Releases
Packages
Used by
Contributors
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GitHub - stac-extensions/sar: Covers synthetic-aperture radar data that represents a snapshot of the earth for a single date and time. · GitHub
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SAR Extension Specification
This document explains the fields of the Synthetic-Aperture Radar (SAR) Extension to the
SpatioTemporal Asset Catalog (STAC) specification.
SAR data is considered to be data that represents a snapshot of the earth for a single date and time taken by a synthetic-aperture radar system
such as Sentinel-1, RADARSAT or EnviSAT.
If the data has been collected by a satellite, it is recommended to use the
Satellite extension.
If the data has been collected on an airborne platform it is recommended to use the
Instrument Fields.
To describe frame start and end times, use the
Date and Time Range fields.
To describe the product type, use the Product extension.
Fields
The fields in the table below can be used in these parts of STAC documents:
  •  Catalogs
  •  Collections
  •  Item Properties (incl. Summaries in Collections)
  •  Assets (for both Collections and Items, incl. Item Asset Definitions in Collections)
  •  Links
Important
In this specification range values are meant to be measured perpendicular to the flight path
and azimuth values are meant to be measured parallel to the flight path.
Field NameTypeDescription
sar:polarizations[string]RECOMMENDED. Any combination of polarizations.
sar:frequency_bandstringRECOMMENDED. The common name for the frequency band to make it easier to search for bands across instruments. See section "Common Frequency Band Names" for a list of accepted names.
sar:center_frequencynumberRECOMMENDED. The center frequency of the radar signal transmitted by the instrument, in gigahertz (GHz).
sar:bandwidthnumberThe range bandwidth of the SAR instrument, in gigahertz (GHz), representing the full bandwidth used in range compression and image formation.
sar:resolution_rangenumberThe range resolution, which is the maximum ability to distinguish two adjacent targets perpendicular to the flight path, in meters (m).
sar:resolution_azimuthnumberThe azimuth resolution, which is the maximum ability to distinguish two adjacent targets parallel to the flight path, in meters (m).
sar:pixel_spacing_rangenumberThe range pixel spacing, which is the distance between adjacent pixels perpendicular to the flight path, in meters (m). Strongly RECOMMENDED to be specified for products of type GRD.
sar:pixel_spacing_azimuthnumberThe azimuth pixel spacing, which is the distance between adjacent pixels parallel to the flight path, in meters (m). Strongly RECOMMENDED to be specified for products of type GRD.
sar:looks_rangenumberNumber of range looks, which is the number of groups of signal samples (looks) perpendicular to the flight path.
sar:looks_azimuthnumberNumber of azimuth looks, which is the number of groups of signal samples (looks) parallel to the flight path.
sar:looks_equivalent_numbernumberThe equivalent number of looks (ENL).
sar:observation_directionstringAntenna pointing direction relative to the flight trajectory of the satellite, either left or right.
sar:relative_burstnumberIdentification number that uniquely identifies a burst cycle within each repeat cycle.
sar:beam_ids[string]Composition of the swath of the SAR acquision referencing the beam identifiers.
sar:product_typestringDEPRECATED in favor of product:type. See Product type.
sar:instrument_modestringDEPRECATED in favor of instrument_modes.
Caution
  • v1.0 of the extension did require sar:product_type.
  • v1.1 deprecates sar:product_type and it's not required any longer, but
product:type is strongly recommended.
  • v2.0 is going to remove sar:product_type.
  • v1.0 of the extension did recommend sar:instrument_mode.
  • v1.3.2 deprecates sar:instrument_mode, but
instrument_modes is strongly recommended.
  • v2.0 is going to remove sar:instrument_mode.
Additional Field Information
sar:polarizations
Specifies a single polarization or a polarization combination.
Allowed values: HH, VV, HV, VH, LH, LV, RH, RV, CH or CV
For single polarized radars, one the allowed values must be set.
For dual polarized radars and alternating polarization, add the corresponding polarizations to the array.
For fully polarimetric radars, add all polarizations to the array.
For instance, for HH+HV, add both HH and HV.
Important
In Item Properties and Collections, sar:polarizations must be a set with unique elements.
In assets sar:polarizations can contain duplicate elements and, if possible, the polarizations must appear in the same order as in the file.
sar:beam_ids
The sar:beam_ids field is used to reference the beam identifiers of the SAR acquisition. According to the mission and the sensor mode,
the beam identifiers can be used to identify the composition of the swath of the SAR acquisition.
The beam identifiers are usually provided in the metadata of the SAR data.
sar:frequency_band - Common Frequency Band Names
The sar:frequency_band is the name that is commonly used to refer to that band's spectral
properties. The table below shows the common name based on the wavelength and frequency ranges for several SAR satellites.
Common NameWavelength Range (cm)Frequency Range (GHz)Satellites
P30 - 1200.25 - 1
L15 - 301 - 2ALOS, JERS, NISAR, SOACOM
S7.5 - 152 - 4HJ-1C
C3.8 - 7.54 - 8EnviSat, ERS, Radarsat, Risat-1, Sentinel-1
X2.4 - 3.88 - 12.5Cosmo-SkyMed, TerraSAR-X, TanDEM-X, PAZ, KOMPSat-5
Ku1.7 - 2.412.5 - 18
K1.1 - 1.718 - 26.5
Ka0.75 - 1.126.5 - 40
Product type
It is RECOMMENDED to include the product:type field.
The product type for SAR data defines the type of processed data contained in the assets.
A list of suggestions for product:type include:
product:typeTypeDescription
SSCcomplexSingle-look Slant-range Complex image (standard SLC)
MGDamplitudeMultilooked Ground-range Detected image
GRDamplitudeMultilooked Ground-range Detected image (used by Sentinel-1)
GECamplitudeGeocoded Ellipsoid Corrected image
GTCamplitudeGeocoded Terrain Corrected image
RTCamplitudeGeocoded Radiometrically Terrain Corrected image
SGCcomplexSingle-look Ground projected Complex image
SLCcomplexSingle-look Ground projected Complex image (used by Sentinel-1)
This can vary by data provider, who all may use slightly different names.
Sentinel-1 for instance uses GRD, which is the same as the more general MGD and SLC instead of SGC.
Date and Time
In SAR, you usually have frame start and end time. To describe this information it is recommended to use the Date and Time Range fields.
The center time of the frame should be specified with the datetime property for STAC Items.
Best Practices
One of the emerging best practices is to use Asset Roles
to provide clients with more information about the assets in an item. The following list includes a shared vocabulary for some common SAR assets.
This list should not be considered definitive, and implementors are welcome to use other asset roles. If consensus and tooling consolidates around
these role names then they will be specified in the future as more standard than just 'best practices'.
Role NameDescription
local-incidence-anglePoints to the local incidence angle file.
ellipsoid-incidence-anglePoints to the ellipsoid incidence angle file.
noise-powerPoints to the noise power file.
amplitudePoints to the intensity file with focused SAR data that has been ground range detected (e.g. GRD).
magnitudePoints to the intensity file where data are represented as complex numbers containing amplitude and phase information (e.g SLC).
sigma0Points to the radar backscatter file where data is referenced in ground surface. It is often derived from an amplitude or a magnitude role asset.
beta0Points to the radar backscatter file where data is referenced in the slant range plane and is radiometrically calibrated. It is often derived from an amplitude or a magnitude role asset.
gamma0Points to the radar backscatter file where data is referenced in the plane perpendicular to the line of sight. It is often derived from an amplitude or a magnitude role asset.
date-offsetPoints to the date-offset file.
covmatPoints to the Points to the Normalized Polarimetric Radar Covariance Matrix (CovMat) file.
prdPoints to the Polarimetric Radar Decomposition (PRD) file.
Contributing
All contributions are subject to the
STAC Specification Code of Conduct.
For contributions, please follow the
STAC specification contributing guide Instructions
for running tests are copied here for convenience.
Running tests
The same checks that run as checks on PR's are part of the repository and can be run locally to verify that changes are valid.
To run tests locally, you'll need npm, which is a standard part of any node.js installation.
First you'll need to install everything with npm once. Just navigate to the root of this repository and on
your command line run:
npm install
Then to check markdown formatting and test the examples against the JSON schema, you can run:
npm test
This will spit out the same texts that you see online, and you can then go and fix your markdown or examples.
If the tests reveal formatting problems with the examples, you can fix them with:
npm run format-examples
About
Covers synthetic-aperture radar data that represents a snapshot of the earth for a single date and time.
Resources
Readme
Apache-2.0 license
Activity
Custom properties
Stars
22 stars
Watchers
6 watching
Forks
10 forks
Report repository
Releases
Packages
Used by
Contributors
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var __re = new RegExp('^' + "youtube\\.com" + '
GitHub - stac-extensions/sar: Covers synthetic-aperture radar data that represents a snapshot of the earth for a single date and time. · GitHub
Skip to content
BranchesTags
Repository files navigation
SAR Extension Specification
This document explains the fields of the Synthetic-Aperture Radar (SAR) Extension to the
SpatioTemporal Asset Catalog (STAC) specification.
SAR data is considered to be data that represents a snapshot of the earth for a single date and time taken by a synthetic-aperture radar system
such as Sentinel-1, RADARSAT or EnviSAT.
If the data has been collected by a satellite, it is recommended to use the
Satellite extension.
If the data has been collected on an airborne platform it is recommended to use the
Instrument Fields.
To describe frame start and end times, use the
Date and Time Range fields.
To describe the product type, use the Product extension.
Fields
The fields in the table below can be used in these parts of STAC documents:
  •  Catalogs
  •  Collections
  •  Item Properties (incl. Summaries in Collections)
  •  Assets (for both Collections and Items, incl. Item Asset Definitions in Collections)
  •  Links
Important
In this specification range values are meant to be measured perpendicular to the flight path
and azimuth values are meant to be measured parallel to the flight path.
Field NameTypeDescription
sar:polarizations[string]RECOMMENDED. Any combination of polarizations.
sar:frequency_bandstringRECOMMENDED. The common name for the frequency band to make it easier to search for bands across instruments. See section "Common Frequency Band Names" for a list of accepted names.
sar:center_frequencynumberRECOMMENDED. The center frequency of the radar signal transmitted by the instrument, in gigahertz (GHz).
sar:bandwidthnumberThe range bandwidth of the SAR instrument, in gigahertz (GHz), representing the full bandwidth used in range compression and image formation.
sar:resolution_rangenumberThe range resolution, which is the maximum ability to distinguish two adjacent targets perpendicular to the flight path, in meters (m).
sar:resolution_azimuthnumberThe azimuth resolution, which is the maximum ability to distinguish two adjacent targets parallel to the flight path, in meters (m).
sar:pixel_spacing_rangenumberThe range pixel spacing, which is the distance between adjacent pixels perpendicular to the flight path, in meters (m). Strongly RECOMMENDED to be specified for products of type GRD.
sar:pixel_spacing_azimuthnumberThe azimuth pixel spacing, which is the distance between adjacent pixels parallel to the flight path, in meters (m). Strongly RECOMMENDED to be specified for products of type GRD.
sar:looks_rangenumberNumber of range looks, which is the number of groups of signal samples (looks) perpendicular to the flight path.
sar:looks_azimuthnumberNumber of azimuth looks, which is the number of groups of signal samples (looks) parallel to the flight path.
sar:looks_equivalent_numbernumberThe equivalent number of looks (ENL).
sar:observation_directionstringAntenna pointing direction relative to the flight trajectory of the satellite, either left or right.
sar:relative_burstnumberIdentification number that uniquely identifies a burst cycle within each repeat cycle.
sar:beam_ids[string]Composition of the swath of the SAR acquision referencing the beam identifiers.
sar:product_typestringDEPRECATED in favor of product:type. See Product type.
sar:instrument_modestringDEPRECATED in favor of instrument_modes.
Caution
  • v1.0 of the extension did require sar:product_type.
  • v1.1 deprecates sar:product_type and it's not required any longer, but
product:type is strongly recommended.
  • v2.0 is going to remove sar:product_type.
  • v1.0 of the extension did recommend sar:instrument_mode.
  • v1.3.2 deprecates sar:instrument_mode, but
instrument_modes is strongly recommended.
  • v2.0 is going to remove sar:instrument_mode.
Additional Field Information
sar:polarizations
Specifies a single polarization or a polarization combination.
Allowed values: HH, VV, HV, VH, LH, LV, RH, RV, CH or CV
For single polarized radars, one the allowed values must be set.
For dual polarized radars and alternating polarization, add the corresponding polarizations to the array.
For fully polarimetric radars, add all polarizations to the array.
For instance, for HH+HV, add both HH and HV.
Important
In Item Properties and Collections, sar:polarizations must be a set with unique elements.
In assets sar:polarizations can contain duplicate elements and, if possible, the polarizations must appear in the same order as in the file.
sar:beam_ids
The sar:beam_ids field is used to reference the beam identifiers of the SAR acquisition. According to the mission and the sensor mode,
the beam identifiers can be used to identify the composition of the swath of the SAR acquisition.
The beam identifiers are usually provided in the metadata of the SAR data.
sar:frequency_band - Common Frequency Band Names
The sar:frequency_band is the name that is commonly used to refer to that band's spectral
properties. The table below shows the common name based on the wavelength and frequency ranges for several SAR satellites.
Common NameWavelength Range (cm)Frequency Range (GHz)Satellites
P30 - 1200.25 - 1
L15 - 301 - 2ALOS, JERS, NISAR, SOACOM
S7.5 - 152 - 4HJ-1C
C3.8 - 7.54 - 8EnviSat, ERS, Radarsat, Risat-1, Sentinel-1
X2.4 - 3.88 - 12.5Cosmo-SkyMed, TerraSAR-X, TanDEM-X, PAZ, KOMPSat-5
Ku1.7 - 2.412.5 - 18
K1.1 - 1.718 - 26.5
Ka0.75 - 1.126.5 - 40
Product type
It is RECOMMENDED to include the product:type field.
The product type for SAR data defines the type of processed data contained in the assets.
A list of suggestions for product:type include:
product:typeTypeDescription
SSCcomplexSingle-look Slant-range Complex image (standard SLC)
MGDamplitudeMultilooked Ground-range Detected image
GRDamplitudeMultilooked Ground-range Detected image (used by Sentinel-1)
GECamplitudeGeocoded Ellipsoid Corrected image
GTCamplitudeGeocoded Terrain Corrected image
RTCamplitudeGeocoded Radiometrically Terrain Corrected image
SGCcomplexSingle-look Ground projected Complex image
SLCcomplexSingle-look Ground projected Complex image (used by Sentinel-1)
This can vary by data provider, who all may use slightly different names.
Sentinel-1 for instance uses GRD, which is the same as the more general MGD and SLC instead of SGC.
Date and Time
In SAR, you usually have frame start and end time. To describe this information it is recommended to use the Date and Time Range fields.
The center time of the frame should be specified with the datetime property for STAC Items.
Best Practices
One of the emerging best practices is to use Asset Roles
to provide clients with more information about the assets in an item. The following list includes a shared vocabulary for some common SAR assets.
This list should not be considered definitive, and implementors are welcome to use other asset roles. If consensus and tooling consolidates around
these role names then they will be specified in the future as more standard than just 'best practices'.
Role NameDescription
local-incidence-anglePoints to the local incidence angle file.
ellipsoid-incidence-anglePoints to the ellipsoid incidence angle file.
noise-powerPoints to the noise power file.
amplitudePoints to the intensity file with focused SAR data that has been ground range detected (e.g. GRD).
magnitudePoints to the intensity file where data are represented as complex numbers containing amplitude and phase information (e.g SLC).
sigma0Points to the radar backscatter file where data is referenced in ground surface. It is often derived from an amplitude or a magnitude role asset.
beta0Points to the radar backscatter file where data is referenced in the slant range plane and is radiometrically calibrated. It is often derived from an amplitude or a magnitude role asset.
gamma0Points to the radar backscatter file where data is referenced in the plane perpendicular to the line of sight. It is often derived from an amplitude or a magnitude role asset.
date-offsetPoints to the date-offset file.
covmatPoints to the Points to the Normalized Polarimetric Radar Covariance Matrix (CovMat) file.
prdPoints to the Polarimetric Radar Decomposition (PRD) file.
Contributing
All contributions are subject to the
STAC Specification Code of Conduct.
For contributions, please follow the
STAC specification contributing guide Instructions
for running tests are copied here for convenience.
Running tests
The same checks that run as checks on PR's are part of the repository and can be run locally to verify that changes are valid.
To run tests locally, you'll need npm, which is a standard part of any node.js installation.
First you'll need to install everything with npm once. Just navigate to the root of this repository and on
your command line run:
npm install
Then to check markdown formatting and test the examples against the JSON schema, you can run:
npm test
This will spit out the same texts that you see online, and you can then go and fix your markdown or examples.
If the tests reveal formatting problems with the examples, you can fix them with:
npm run format-examples
About
Covers synthetic-aperture radar data that represents a snapshot of the earth for a single date and time.
Resources
Readme
Apache-2.0 license
Activity
Custom properties
Stars
22 stars
Watchers
6 watching
Forks
10 forks
Report repository
Releases
Packages
Used by
Contributors
Generated from stac-extensions/template

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GitHub - stac-extensions/sar: Covers synthetic-aperture radar data that represents a snapshot of the earth for a single date and time. · GitHub
Skip to content
BranchesTags
Repository files navigation
SAR Extension Specification
This document explains the fields of the Synthetic-Aperture Radar (SAR) Extension to the
SpatioTemporal Asset Catalog (STAC) specification.
SAR data is considered to be data that represents a snapshot of the earth for a single date and time taken by a synthetic-aperture radar system
such as Sentinel-1, RADARSAT or EnviSAT.
If the data has been collected by a satellite, it is recommended to use the
Satellite extension.
If the data has been collected on an airborne platform it is recommended to use the
Instrument Fields.
To describe frame start and end times, use the
Date and Time Range fields.
To describe the product type, use the Product extension.
Fields
The fields in the table below can be used in these parts of STAC documents:
  •  Catalogs
  •  Collections
  •  Item Properties (incl. Summaries in Collections)
  •  Assets (for both Collections and Items, incl. Item Asset Definitions in Collections)
  •  Links
Important
In this specification range values are meant to be measured perpendicular to the flight path
and azimuth values are meant to be measured parallel to the flight path.
Field NameTypeDescription
sar:polarizations[string]RECOMMENDED. Any combination of polarizations.
sar:frequency_bandstringRECOMMENDED. The common name for the frequency band to make it easier to search for bands across instruments. See section "Common Frequency Band Names" for a list of accepted names.
sar:center_frequencynumberRECOMMENDED. The center frequency of the radar signal transmitted by the instrument, in gigahertz (GHz).
sar:bandwidthnumberThe range bandwidth of the SAR instrument, in gigahertz (GHz), representing the full bandwidth used in range compression and image formation.
sar:resolution_rangenumberThe range resolution, which is the maximum ability to distinguish two adjacent targets perpendicular to the flight path, in meters (m).
sar:resolution_azimuthnumberThe azimuth resolution, which is the maximum ability to distinguish two adjacent targets parallel to the flight path, in meters (m).
sar:pixel_spacing_rangenumberThe range pixel spacing, which is the distance between adjacent pixels perpendicular to the flight path, in meters (m). Strongly RECOMMENDED to be specified for products of type GRD.
sar:pixel_spacing_azimuthnumberThe azimuth pixel spacing, which is the distance between adjacent pixels parallel to the flight path, in meters (m). Strongly RECOMMENDED to be specified for products of type GRD.
sar:looks_rangenumberNumber of range looks, which is the number of groups of signal samples (looks) perpendicular to the flight path.
sar:looks_azimuthnumberNumber of azimuth looks, which is the number of groups of signal samples (looks) parallel to the flight path.
sar:looks_equivalent_numbernumberThe equivalent number of looks (ENL).
sar:observation_directionstringAntenna pointing direction relative to the flight trajectory of the satellite, either left or right.
sar:relative_burstnumberIdentification number that uniquely identifies a burst cycle within each repeat cycle.
sar:beam_ids[string]Composition of the swath of the SAR acquision referencing the beam identifiers.
sar:product_typestringDEPRECATED in favor of product:type. See Product type.
sar:instrument_modestringDEPRECATED in favor of instrument_modes.
Caution
  • v1.0 of the extension did require sar:product_type.
  • v1.1 deprecates sar:product_type and it's not required any longer, but
product:type is strongly recommended.
  • v2.0 is going to remove sar:product_type.
  • v1.0 of the extension did recommend sar:instrument_mode.
  • v1.3.2 deprecates sar:instrument_mode, but
instrument_modes is strongly recommended.
  • v2.0 is going to remove sar:instrument_mode.
Additional Field Information
sar:polarizations
Specifies a single polarization or a polarization combination.
Allowed values: HH, VV, HV, VH, LH, LV, RH, RV, CH or CV
For single polarized radars, one the allowed values must be set.
For dual polarized radars and alternating polarization, add the corresponding polarizations to the array.
For fully polarimetric radars, add all polarizations to the array.
For instance, for HH+HV, add both HH and HV.
Important
In Item Properties and Collections, sar:polarizations must be a set with unique elements.
In assets sar:polarizations can contain duplicate elements and, if possible, the polarizations must appear in the same order as in the file.
sar:beam_ids
The sar:beam_ids field is used to reference the beam identifiers of the SAR acquisition. According to the mission and the sensor mode,
the beam identifiers can be used to identify the composition of the swath of the SAR acquisition.
The beam identifiers are usually provided in the metadata of the SAR data.
sar:frequency_band - Common Frequency Band Names
The sar:frequency_band is the name that is commonly used to refer to that band's spectral
properties. The table below shows the common name based on the wavelength and frequency ranges for several SAR satellites.
Common NameWavelength Range (cm)Frequency Range (GHz)Satellites
P30 - 1200.25 - 1
L15 - 301 - 2ALOS, JERS, NISAR, SOACOM
S7.5 - 152 - 4HJ-1C
C3.8 - 7.54 - 8EnviSat, ERS, Radarsat, Risat-1, Sentinel-1
X2.4 - 3.88 - 12.5Cosmo-SkyMed, TerraSAR-X, TanDEM-X, PAZ, KOMPSat-5
Ku1.7 - 2.412.5 - 18
K1.1 - 1.718 - 26.5
Ka0.75 - 1.126.5 - 40
Product type
It is RECOMMENDED to include the product:type field.
The product type for SAR data defines the type of processed data contained in the assets.
A list of suggestions for product:type include:
product:typeTypeDescription
SSCcomplexSingle-look Slant-range Complex image (standard SLC)
MGDamplitudeMultilooked Ground-range Detected image
GRDamplitudeMultilooked Ground-range Detected image (used by Sentinel-1)
GECamplitudeGeocoded Ellipsoid Corrected image
GTCamplitudeGeocoded Terrain Corrected image
RTCamplitudeGeocoded Radiometrically Terrain Corrected image
SGCcomplexSingle-look Ground projected Complex image
SLCcomplexSingle-look Ground projected Complex image (used by Sentinel-1)
This can vary by data provider, who all may use slightly different names.
Sentinel-1 for instance uses GRD, which is the same as the more general MGD and SLC instead of SGC.
Date and Time
In SAR, you usually have frame start and end time. To describe this information it is recommended to use the Date and Time Range fields.
The center time of the frame should be specified with the datetime property for STAC Items.
Best Practices
One of the emerging best practices is to use Asset Roles
to provide clients with more information about the assets in an item. The following list includes a shared vocabulary for some common SAR assets.
This list should not be considered definitive, and implementors are welcome to use other asset roles. If consensus and tooling consolidates around
these role names then they will be specified in the future as more standard than just 'best practices'.
Role NameDescription
local-incidence-anglePoints to the local incidence angle file.
ellipsoid-incidence-anglePoints to the ellipsoid incidence angle file.
noise-powerPoints to the noise power file.
amplitudePoints to the intensity file with focused SAR data that has been ground range detected (e.g. GRD).
magnitudePoints to the intensity file where data are represented as complex numbers containing amplitude and phase information (e.g SLC).
sigma0Points to the radar backscatter file where data is referenced in ground surface. It is often derived from an amplitude or a magnitude role asset.
beta0Points to the radar backscatter file where data is referenced in the slant range plane and is radiometrically calibrated. It is often derived from an amplitude or a magnitude role asset.
gamma0Points to the radar backscatter file where data is referenced in the plane perpendicular to the line of sight. It is often derived from an amplitude or a magnitude role asset.
date-offsetPoints to the date-offset file.
covmatPoints to the Points to the Normalized Polarimetric Radar Covariance Matrix (CovMat) file.
prdPoints to the Polarimetric Radar Decomposition (PRD) file.
Contributing
All contributions are subject to the
STAC Specification Code of Conduct.
For contributions, please follow the
STAC specification contributing guide Instructions
for running tests are copied here for convenience.
Running tests
The same checks that run as checks on PR's are part of the repository and can be run locally to verify that changes are valid.
To run tests locally, you'll need npm, which is a standard part of any node.js installation.
First you'll need to install everything with npm once. Just navigate to the root of this repository and on
your command line run:
npm install
Then to check markdown formatting and test the examples against the JSON schema, you can run:
npm test
This will spit out the same texts that you see online, and you can then go and fix your markdown or examples.
If the tests reveal formatting problems with the examples, you can fix them with:
npm run format-examples
About
Covers synthetic-aperture radar data that represents a snapshot of the earth for a single date and time.
Resources
Readme
Apache-2.0 license
Activity
Custom properties
Stars
22 stars
Watchers
6 watching
Forks
10 forks
Report repository
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GitHub - stac-extensions/sar: Covers synthetic-aperture radar data that represents a snapshot of the earth for a single date and time. · GitHub
Skip to content
BranchesTags
Repository files navigation
SAR Extension Specification
This document explains the fields of the Synthetic-Aperture Radar (SAR) Extension to the
SpatioTemporal Asset Catalog (STAC) specification.
SAR data is considered to be data that represents a snapshot of the earth for a single date and time taken by a synthetic-aperture radar system
such as Sentinel-1, RADARSAT or EnviSAT.
If the data has been collected by a satellite, it is recommended to use the
Satellite extension.
If the data has been collected on an airborne platform it is recommended to use the
Instrument Fields.
To describe frame start and end times, use the
Date and Time Range fields.
To describe the product type, use the Product extension.
Fields
The fields in the table below can be used in these parts of STAC documents:
  •  Catalogs
  •  Collections
  •  Item Properties (incl. Summaries in Collections)
  •  Assets (for both Collections and Items, incl. Item Asset Definitions in Collections)
  •  Links
Important
In this specification range values are meant to be measured perpendicular to the flight path
and azimuth values are meant to be measured parallel to the flight path.
Field NameTypeDescription
sar:polarizations[string]RECOMMENDED. Any combination of polarizations.
sar:frequency_bandstringRECOMMENDED. The common name for the frequency band to make it easier to search for bands across instruments. See section "Common Frequency Band Names" for a list of accepted names.
sar:center_frequencynumberRECOMMENDED. The center frequency of the radar signal transmitted by the instrument, in gigahertz (GHz).
sar:bandwidthnumberThe range bandwidth of the SAR instrument, in gigahertz (GHz), representing the full bandwidth used in range compression and image formation.
sar:resolution_rangenumberThe range resolution, which is the maximum ability to distinguish two adjacent targets perpendicular to the flight path, in meters (m).
sar:resolution_azimuthnumberThe azimuth resolution, which is the maximum ability to distinguish two adjacent targets parallel to the flight path, in meters (m).
sar:pixel_spacing_rangenumberThe range pixel spacing, which is the distance between adjacent pixels perpendicular to the flight path, in meters (m). Strongly RECOMMENDED to be specified for products of type GRD.
sar:pixel_spacing_azimuthnumberThe azimuth pixel spacing, which is the distance between adjacent pixels parallel to the flight path, in meters (m). Strongly RECOMMENDED to be specified for products of type GRD.
sar:looks_rangenumberNumber of range looks, which is the number of groups of signal samples (looks) perpendicular to the flight path.
sar:looks_azimuthnumberNumber of azimuth looks, which is the number of groups of signal samples (looks) parallel to the flight path.
sar:looks_equivalent_numbernumberThe equivalent number of looks (ENL).
sar:observation_directionstringAntenna pointing direction relative to the flight trajectory of the satellite, either left or right.
sar:relative_burstnumberIdentification number that uniquely identifies a burst cycle within each repeat cycle.
sar:beam_ids[string]Composition of the swath of the SAR acquision referencing the beam identifiers.
sar:product_typestringDEPRECATED in favor of product:type. See Product type.
sar:instrument_modestringDEPRECATED in favor of instrument_modes.
Caution
  • v1.0 of the extension did require sar:product_type.
  • v1.1 deprecates sar:product_type and it's not required any longer, but
product:type is strongly recommended.
  • v2.0 is going to remove sar:product_type.
  • v1.0 of the extension did recommend sar:instrument_mode.
  • v1.3.2 deprecates sar:instrument_mode, but
instrument_modes is strongly recommended.
  • v2.0 is going to remove sar:instrument_mode.
Additional Field Information
sar:polarizations
Specifies a single polarization or a polarization combination.
Allowed values: HH, VV, HV, VH, LH, LV, RH, RV, CH or CV
For single polarized radars, one the allowed values must be set.
For dual polarized radars and alternating polarization, add the corresponding polarizations to the array.
For fully polarimetric radars, add all polarizations to the array.
For instance, for HH+HV, add both HH and HV.
Important
In Item Properties and Collections, sar:polarizations must be a set with unique elements.
In assets sar:polarizations can contain duplicate elements and, if possible, the polarizations must appear in the same order as in the file.
sar:beam_ids
The sar:beam_ids field is used to reference the beam identifiers of the SAR acquisition. According to the mission and the sensor mode,
the beam identifiers can be used to identify the composition of the swath of the SAR acquisition.
The beam identifiers are usually provided in the metadata of the SAR data.
sar:frequency_band - Common Frequency Band Names
The sar:frequency_band is the name that is commonly used to refer to that band's spectral
properties. The table below shows the common name based on the wavelength and frequency ranges for several SAR satellites.
Common NameWavelength Range (cm)Frequency Range (GHz)Satellites
P30 - 1200.25 - 1
L15 - 301 - 2ALOS, JERS, NISAR, SOACOM
S7.5 - 152 - 4HJ-1C
C3.8 - 7.54 - 8EnviSat, ERS, Radarsat, Risat-1, Sentinel-1
X2.4 - 3.88 - 12.5Cosmo-SkyMed, TerraSAR-X, TanDEM-X, PAZ, KOMPSat-5
Ku1.7 - 2.412.5 - 18
K1.1 - 1.718 - 26.5
Ka0.75 - 1.126.5 - 40
Product type
It is RECOMMENDED to include the product:type field.
The product type for SAR data defines the type of processed data contained in the assets.
A list of suggestions for product:type include:
product:typeTypeDescription
SSCcomplexSingle-look Slant-range Complex image (standard SLC)
MGDamplitudeMultilooked Ground-range Detected image
GRDamplitudeMultilooked Ground-range Detected image (used by Sentinel-1)
GECamplitudeGeocoded Ellipsoid Corrected image
GTCamplitudeGeocoded Terrain Corrected image
RTCamplitudeGeocoded Radiometrically Terrain Corrected image
SGCcomplexSingle-look Ground projected Complex image
SLCcomplexSingle-look Ground projected Complex image (used by Sentinel-1)
This can vary by data provider, who all may use slightly different names.
Sentinel-1 for instance uses GRD, which is the same as the more general MGD and SLC instead of SGC.
Date and Time
In SAR, you usually have frame start and end time. To describe this information it is recommended to use the Date and Time Range fields.
The center time of the frame should be specified with the datetime property for STAC Items.
Best Practices
One of the emerging best practices is to use Asset Roles
to provide clients with more information about the assets in an item. The following list includes a shared vocabulary for some common SAR assets.
This list should not be considered definitive, and implementors are welcome to use other asset roles. If consensus and tooling consolidates around
these role names then they will be specified in the future as more standard than just 'best practices'.
Role NameDescription
local-incidence-anglePoints to the local incidence angle file.
ellipsoid-incidence-anglePoints to the ellipsoid incidence angle file.
noise-powerPoints to the noise power file.
amplitudePoints to the intensity file with focused SAR data that has been ground range detected (e.g. GRD).
magnitudePoints to the intensity file where data are represented as complex numbers containing amplitude and phase information (e.g SLC).
sigma0Points to the radar backscatter file where data is referenced in ground surface. It is often derived from an amplitude or a magnitude role asset.
beta0Points to the radar backscatter file where data is referenced in the slant range plane and is radiometrically calibrated. It is often derived from an amplitude or a magnitude role asset.
gamma0Points to the radar backscatter file where data is referenced in the plane perpendicular to the line of sight. It is often derived from an amplitude or a magnitude role asset.
date-offsetPoints to the date-offset file.
covmatPoints to the Points to the Normalized Polarimetric Radar Covariance Matrix (CovMat) file.
prdPoints to the Polarimetric Radar Decomposition (PRD) file.
Contributing
All contributions are subject to the
STAC Specification Code of Conduct.
For contributions, please follow the
STAC specification contributing guide Instructions
for running tests are copied here for convenience.
Running tests
The same checks that run as checks on PR's are part of the repository and can be run locally to verify that changes are valid.
To run tests locally, you'll need npm, which is a standard part of any node.js installation.
First you'll need to install everything with npm once. Just navigate to the root of this repository and on
your command line run:
npm install
Then to check markdown formatting and test the examples against the JSON schema, you can run:
npm test
This will spit out the same texts that you see online, and you can then go and fix your markdown or examples.
If the tests reveal formatting problems with the examples, you can fix them with:
npm run format-examples
About
Covers synthetic-aperture radar data that represents a snapshot of the earth for a single date and time.
Resources
Readme
Apache-2.0 license
Activity
Custom properties
Stars
22 stars
Watchers
6 watching
Forks
10 forks
Report repository
Releases
Packages
Used by
Contributors
Generated from stac-extensions/template

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GitHub - stac-extensions/sar: Covers synthetic-aperture radar data that represents a snapshot of the earth for a single date and time. · GitHub
Skip to content
BranchesTags
Repository files navigation
SAR Extension Specification
This document explains the fields of the Synthetic-Aperture Radar (SAR) Extension to the
SpatioTemporal Asset Catalog (STAC) specification.
SAR data is considered to be data that represents a snapshot of the earth for a single date and time taken by a synthetic-aperture radar system
such as Sentinel-1, RADARSAT or EnviSAT.
If the data has been collected by a satellite, it is recommended to use the
Satellite extension.
If the data has been collected on an airborne platform it is recommended to use the
Instrument Fields.
To describe frame start and end times, use the
Date and Time Range fields.
To describe the product type, use the Product extension.
Fields
The fields in the table below can be used in these parts of STAC documents:
  •  Catalogs
  •  Collections
  •  Item Properties (incl. Summaries in Collections)
  •  Assets (for both Collections and Items, incl. Item Asset Definitions in Collections)
  •  Links
Important
In this specification range values are meant to be measured perpendicular to the flight path
and azimuth values are meant to be measured parallel to the flight path.
Field NameTypeDescription
sar:polarizations[string]RECOMMENDED. Any combination of polarizations.
sar:frequency_bandstringRECOMMENDED. The common name for the frequency band to make it easier to search for bands across instruments. See section "Common Frequency Band Names" for a list of accepted names.
sar:center_frequencynumberRECOMMENDED. The center frequency of the radar signal transmitted by the instrument, in gigahertz (GHz).
sar:bandwidthnumberThe range bandwidth of the SAR instrument, in gigahertz (GHz), representing the full bandwidth used in range compression and image formation.
sar:resolution_rangenumberThe range resolution, which is the maximum ability to distinguish two adjacent targets perpendicular to the flight path, in meters (m).
sar:resolution_azimuthnumberThe azimuth resolution, which is the maximum ability to distinguish two adjacent targets parallel to the flight path, in meters (m).
sar:pixel_spacing_rangenumberThe range pixel spacing, which is the distance between adjacent pixels perpendicular to the flight path, in meters (m). Strongly RECOMMENDED to be specified for products of type GRD.
sar:pixel_spacing_azimuthnumberThe azimuth pixel spacing, which is the distance between adjacent pixels parallel to the flight path, in meters (m). Strongly RECOMMENDED to be specified for products of type GRD.
sar:looks_rangenumberNumber of range looks, which is the number of groups of signal samples (looks) perpendicular to the flight path.
sar:looks_azimuthnumberNumber of azimuth looks, which is the number of groups of signal samples (looks) parallel to the flight path.
sar:looks_equivalent_numbernumberThe equivalent number of looks (ENL).
sar:observation_directionstringAntenna pointing direction relative to the flight trajectory of the satellite, either left or right.
sar:relative_burstnumberIdentification number that uniquely identifies a burst cycle within each repeat cycle.
sar:beam_ids[string]Composition of the swath of the SAR acquision referencing the beam identifiers.
sar:product_typestringDEPRECATED in favor of product:type. See Product type.
sar:instrument_modestringDEPRECATED in favor of instrument_modes.
Caution
  • v1.0 of the extension did require sar:product_type.
  • v1.1 deprecates sar:product_type and it's not required any longer, but
product:type is strongly recommended.
  • v2.0 is going to remove sar:product_type.
  • v1.0 of the extension did recommend sar:instrument_mode.
  • v1.3.2 deprecates sar:instrument_mode, but
instrument_modes is strongly recommended.
  • v2.0 is going to remove sar:instrument_mode.
Additional Field Information
sar:polarizations
Specifies a single polarization or a polarization combination.
Allowed values: HH, VV, HV, VH, LH, LV, RH, RV, CH or CV
For single polarized radars, one the allowed values must be set.
For dual polarized radars and alternating polarization, add the corresponding polarizations to the array.
For fully polarimetric radars, add all polarizations to the array.
For instance, for HH+HV, add both HH and HV.
Important
In Item Properties and Collections, sar:polarizations must be a set with unique elements.
In assets sar:polarizations can contain duplicate elements and, if possible, the polarizations must appear in the same order as in the file.
sar:beam_ids
The sar:beam_ids field is used to reference the beam identifiers of the SAR acquisition. According to the mission and the sensor mode,
the beam identifiers can be used to identify the composition of the swath of the SAR acquisition.
The beam identifiers are usually provided in the metadata of the SAR data.
sar:frequency_band - Common Frequency Band Names
The sar:frequency_band is the name that is commonly used to refer to that band's spectral
properties. The table below shows the common name based on the wavelength and frequency ranges for several SAR satellites.
Common NameWavelength Range (cm)Frequency Range (GHz)Satellites
P30 - 1200.25 - 1
L15 - 301 - 2ALOS, JERS, NISAR, SOACOM
S7.5 - 152 - 4HJ-1C
C3.8 - 7.54 - 8EnviSat, ERS, Radarsat, Risat-1, Sentinel-1
X2.4 - 3.88 - 12.5Cosmo-SkyMed, TerraSAR-X, TanDEM-X, PAZ, KOMPSat-5
Ku1.7 - 2.412.5 - 18
K1.1 - 1.718 - 26.5
Ka0.75 - 1.126.5 - 40
Product type
It is RECOMMENDED to include the product:type field.
The product type for SAR data defines the type of processed data contained in the assets.
A list of suggestions for product:type include:
product:typeTypeDescription
SSCcomplexSingle-look Slant-range Complex image (standard SLC)
MGDamplitudeMultilooked Ground-range Detected image
GRDamplitudeMultilooked Ground-range Detected image (used by Sentinel-1)
GECamplitudeGeocoded Ellipsoid Corrected image
GTCamplitudeGeocoded Terrain Corrected image
RTCamplitudeGeocoded Radiometrically Terrain Corrected image
SGCcomplexSingle-look Ground projected Complex image
SLCcomplexSingle-look Ground projected Complex image (used by Sentinel-1)
This can vary by data provider, who all may use slightly different names.
Sentinel-1 for instance uses GRD, which is the same as the more general MGD and SLC instead of SGC.
Date and Time
In SAR, you usually have frame start and end time. To describe this information it is recommended to use the Date and Time Range fields.
The center time of the frame should be specified with the datetime property for STAC Items.
Best Practices
One of the emerging best practices is to use Asset Roles
to provide clients with more information about the assets in an item. The following list includes a shared vocabulary for some common SAR assets.
This list should not be considered definitive, and implementors are welcome to use other asset roles. If consensus and tooling consolidates around
these role names then they will be specified in the future as more standard than just 'best practices'.
Role NameDescription
local-incidence-anglePoints to the local incidence angle file.
ellipsoid-incidence-anglePoints to the ellipsoid incidence angle file.
noise-powerPoints to the noise power file.
amplitudePoints to the intensity file with focused SAR data that has been ground range detected (e.g. GRD).
magnitudePoints to the intensity file where data are represented as complex numbers containing amplitude and phase information (e.g SLC).
sigma0Points to the radar backscatter file where data is referenced in ground surface. It is often derived from an amplitude or a magnitude role asset.
beta0Points to the radar backscatter file where data is referenced in the slant range plane and is radiometrically calibrated. It is often derived from an amplitude or a magnitude role asset.
gamma0Points to the radar backscatter file where data is referenced in the plane perpendicular to the line of sight. It is often derived from an amplitude or a magnitude role asset.
date-offsetPoints to the date-offset file.
covmatPoints to the Points to the Normalized Polarimetric Radar Covariance Matrix (CovMat) file.
prdPoints to the Polarimetric Radar Decomposition (PRD) file.
Contributing
All contributions are subject to the
STAC Specification Code of Conduct.
For contributions, please follow the
STAC specification contributing guide Instructions
for running tests are copied here for convenience.
Running tests
The same checks that run as checks on PR's are part of the repository and can be run locally to verify that changes are valid.
To run tests locally, you'll need npm, which is a standard part of any node.js installation.
First you'll need to install everything with npm once. Just navigate to the root of this repository and on
your command line run:
npm install
Then to check markdown formatting and test the examples against the JSON schema, you can run:
npm test
This will spit out the same texts that you see online, and you can then go and fix your markdown or examples.
If the tests reveal formatting problems with the examples, you can fix them with:
npm run format-examples
About
Covers synthetic-aperture radar data that represents a snapshot of the earth for a single date and time.
Resources
Readme
Apache-2.0 license
Activity
Custom properties
Stars
22 stars
Watchers
6 watching
Forks
10 forks
Report repository
Releases
Packages
Used by
Contributors
Generated from stac-extensions/template