Landsat Collection 2 Level-2 Surface Reflectance

Date modified: 14 February 2022

Product overview

Background

Digital Earth Africa (DE Africa) provides free and open access to a copy of Landsat Collection 2 Level-2 products over Africa. These products are produced and provided by the United States Geological Survey (USGS).

The Landsat series of Earth Observation satellites, jointly led by USGS and NASA, have been continuously acquiring images of the Earth’s land surface since 1972. DE Africa provides data from Landsat 5, 7, 8, and 9 satellites, including historical observations dating back to late 1980s and regularly updated new acquisitions.

New Level-2 Landsat 7, 8, and 9 data are available after approximately 25, 15, and 3 days, respectively, from acquisition. See Landsat Collection 2 Generation Timeline for details.

USGS Landsat Collection 2 was released early 2021 and offers improved processing, geometric accuracy, and radiometric calibration compared to previous Collection 1 products. The Level-2 products are endorsed by the Committee on Earth Observation Satellites (CEOS) to be Analysis Ready Data (CARD)-compliant. This internationally-recognised certification ensures these products have been processed to a minimum set of requirements and organised into a form that allows immediate analysis with a minimum of additional user effort and interoperability both through time and with other datasets.

USGS Landsat Collection 2 Level-2 includes:

• Surface Reflectance

• Surface Temperature

This document provides technical specifications for the Surface Reflectance product. Information for the Surface Temperature product can be found in the Landsat Collection 2 Level-2 Surface Temperature specification.

Surface reflectance is the fraction of incoming solar radiation that is reflected from Earth’s surface. Variations in satellite measured radiance due to atmospheric properties have been corrected for so images acquired over the same area at different times are comparable and can be used readily to detect changes on Earth’s surface.

A Jupyter Notebook which demonstrates loading and using Landsat surface reflectance products in the Sandbox is also available.

Specifications

Spatial and temporal coverage

DE Africa provides Landsat Collection 2 Level-2 from Landsat 5, 7, 8, and 9 as seperate products. Relevant coverage and metadata can be viewed on DE Africa Metadata Exploer:

• Landsat 5 Collection 2 Level-2 Surface Reflectance

• Landsat 7 Collection 2 Level-2 Surface Reflectance

• Landsat 8 Collection 2 Level-2 Surface Reflectance

• Landsat 9 Collection 2 Level-2 Surface Reflectance

Table 1: Landsat Collection 2 Level-2 Surface Reflectance product specifications

Satellite	Landsat 5	Landsat 7	Landsat 8	Landsat 9
Instrument	Multispectral Scanner (MSS), Thematic Mapper (TM)	Enhanced Thematic Mapper (ETM+)	Operational Land Imager (OLI), Thermal Infrared Sensor (TIRS)	OLI-2, TIRS-2
Number of bands	10	10	10	10
Cell size - X (metres)	30	30	30	30
Cell size - Y (metres)	30	30	30	30
Coordinate reference system	Universal Transverse Mercator (UTM)	UTM	UTM	UTM
Temporal resolution	Every 16 days	Every 16 days	Every 16 days	Every 16 days
Temporal range	1984 – 2012	1999 – present	2013 – present	2021 – present
Parent dataset	Landsat Collection 2 Level-1	Landsat Collection 2 Level-1	Landsat Collection 2 Level-1	Landsat Collection 2 Level-1
Update frequency	NA (archive)	Daily	Daily	Daily

Measurements

Table 2: Landsat 5 and Landsat 7 Level-2 Surface Reflectance measurements

Band ID	Description	Units	Range	Data type	No data\(^\dagger\)	Conversion\(^\ddagger\)
SR_B1	Surface reflectance band 1 (Blue)	Unitless	1-65455	uint16	0	2.75e-05 * DN - 0.2
SR_B2	Surface reflectance band 2 (Green)	Unitless	1-65455	uint16	0	2.75e-05 * DN - 0.2
SR_B3	Surface reflectance band 3 (Red)	Unitless	1-65455	uint16	0	2.75e-05 * DN - 0.2
SR_B4	Surface reflectance band 4 (Near-Infrared (NIR))	Unitless	1-65455	uint16	0	2.75e-05 * DN - 0.2
SR_B5	Surface reflectance band 5 (Short Wavelength Infrared (SWIR) 1)	Unitless	1-65455	uint16	0	2.75e-05 * DN - 0.2
SR_B7	Surface reflectance band 7 (SWIR 2)	Unitless	1-65455	uint16	0	2.75e-05 * DN - 0.2
QA_PIXEL	Pixel quality	Bit Index	0-65535	uint16	1	NA
QA_RADSAT	Radiometric saturation	Bit Index	0-65535	uint16	0	NA
SR_ATMOS _OPACITY	Atmospheric opacity	Unitless	0-32767	int16	-9999	0.001 * DN
SR_CLOUD _QA	Cloud mask quality	Bit Index	0-255	uint8	0	NA

\(^\dagger\) No data or fill value.

\(^\ddagger\) Physical measurement can be derived from the Digital Number (DN) stored in the product using the conversion equation listed.

More inforamtion can be found from the Landsat 4-7 Collection 2 Science Product Guide.

Table 3: Landsat 8 and Landsat 9 Level-2 Surface Reflectance measurements

Landsat 8 and Landsat 9 Level-2 science products are generated using a different algorithm and have different output measurements compared to Landsat 5 and Landsat 7.

Band ID	Description	Units	Range	Data type	No data\(^\dagger\)	Conversion\(^\ddagger\)
SR_B1	Surface reflectance band 1 (Coastal Aerosol)	Unitless	1-65455	uint16	0	2.75e-05 * DN - 0.2
SR_B2	Surface reflectance band 2 (Blue)	Unitless	1-65455	uint16	0	2.75e-05 * DN - 0.2
SR_B3	Surface reflectance band 3 (Green)	Unitless	1-65455	uint16	0	2.75e-05 * DN - 0.2
SR_B4	Surface reflectance band 4 (Red)	Unitless	1-65455	uint16	0	2.75e-05 * DN - 0.2
SR_B5	Surface reflectance band 5 (NIR)	Unitless	1-65455	uint16	0	2.75e-05 * DN - 0.2
SR_B6	Surface reflectance band 6 (SWIR 1)	Unitless	1-65455	uint16	0	2.75e-05 * DN - 0.2
SR_B7	Surface reflectance band 7 (SWIR 2)	Unitless	1-65455	uint16	0	2.75e-05 * DN - 0.2
QA_PIXEL	Pixel quality	Bit Index	0-65535	uint16	1	NA
QA_RADSAT	Radiometric saturation	Bit Index	0-65535	uint16	0	NA
SR_QA _AEROSOL	Aerosol level	Bit Index	0-255	uint8	1	NA

\(^\dagger\) No data or fill value.

\(^\ddagger\) Physical measurement can be derived from the Digital Number (DN) stored in the product using the conversion equation listed.

More inforamtion can be found from Landsat 8 OLI/TIRS Collection 2 Science Product Guide and Landsat 8-9 OLI/TIRS Collection 2 Level 2 Data Format Control Book

Quality assessment bands

Pixel quality assessment (QA_PIXEL) bands are generated by the CFMask algorithm. Different bit definitions are used because the cirrus band is only available on Landsat 8 and 9. This band is relevant to both Surface Reflectance and Surface Temperature products.

Table 4: Pixel quality assessment (QA_PIXEL) bit index.

Bit	Landat 5 & 7	Landsat 8 & 9	Description Values
0	Fill	Fill	0 for image data; 1 for fill data
1	Dilated Cloud	Dilated Cloud	0 for cloud is not dilated or no cloud; 1 for cloud dilation
2	Unused	Cirrus	0 for cirrus confidence is not; 1 for high confidence cirrus
3	Cloud	Cloud	0 for cloud confidence is not high; 1 for high confidence cloud
4	Cloud Shadow	Cloud Shadow	0 for Cloud Shadow Confidence is not high; 1 for high confidence cloud shadow
5	Snow	Snow	0 for Snow/Ice Confidence is not high; 1 for high confidence snow cover
6	Clear	Clear	0 if Cloud or Dilated Cloud bits are set; 1 if Cloud and Dilated Cloud bits are not set
7	Water	Water	0 for land or cloud; 1 for water
8-9	Cloud Confidence	Cloud Confidence	00 for no confidence level set; 01 Low confidence; 10 Medium confidence; 11 High confidence
10-11	Cloud Shadow Confidence	Cloud Shadow Confidence	00 for no confidence level set; 01 Low confidence; 10 Reserved; 11 High confidence
12-13	Snow/Ice Confidence	Snow/Ice Confidence	00 for no confidence level set; 01 Low confidence; 10 Reserved; 11 High confidence
14-15	Unused	Cirrus Confidence	00 for no confidence level set; 01 Low confidence; 10 Reserved; 11 High confidence

Radiometric saturation quality assessment (QA_RADSAT) bands are different for Landsat 5, 7 and 8/9 because the sensors have different spectral bands. This band is relevant to both Surface Reflectance and Surface Temperature products.

Table 5: Radiometric saturation quality assessment (QA_RADSAT) bit index.

Bit	Landsat 5	Landsat 7	Landsat 8 & 9	Description Values
0	Band 1 (Blue)	Band 1 (Blue)	Band 1 (Coastal)	0 no saturation; 1 saturated data
1	Band 2 (Green)	Band 2 (Green)	Band 2 (Blue)	0 no saturation; 1 saturated data
2	Band 3 (Red)	Band 3 (Red)	Band 3 (Green)	0 no saturation; 1 saturated data
3	Band 4 (NIR)	Band 4 (NIR)	Band 4 (Red)	0 no saturation; 1 saturated data
4	Band 5 (SWIR1)	Band 5 (SWIR1)	Band 5 (NIR)	0 no saturation; 1 saturated data
5	Band 6 (TIR)	Band 6L (TIR)†	Band 6 (SWIR1)	0 no saturation; 1 saturated data
6	Band 7 (SWIR2)	Band 7 (SWIR2)	Band 7 (SWIR2)	0 no saturation; 1 saturated data
7	Unused	Unused	Unused	0
8	Unused	Band 6H (TIR)‡	Band 9 (Cirrus)	0 no saturation; 1 saturated data
9	Dropped Pixel	Dropped Pixel	Unused	0 Pixel present; 1 detector doesn’t have a value - no data
10	Unused	Unused	Unused	0
11	Unused	Unused	Terrain occlusion	0 no terrain occlusion; 1 terrain occlusion
12	Unused	Unused	Unused	0
13	Unused	Unused	Unused	0
14	Unused	Unused	Unused	0
15	Unused	Unused	Unused	0

\(^\dagger\), \(^\ddagger\) For Landsat 7 products, the Band 6 TOA brightness temperature product is generated from ETM+ Band 6 High gain (6H) and Band 6 Low gain (6L) merged together. The merged Band 6 is comprised of pixels that are not saturated in Band 6H. When Band 6H pixels are saturated with a brightness temperature outside of the 6H dynamic range (from 240K to 322K), they will be filled with pixels from the 6L band even if those pixels are saturated.

For Landsat 5 and 7, another cloud mask band (SR_CLOUD_QA) is available but is less accurate than the QA_PIXEL band.

Table 6: Landsat 5 and Landsat 7 cloud mask (SR_CLOUD_QA) bit index.

Bit	Attribute
0	Dark Dense Vegetation (DDV)
1	Cloud
2	Cloud shadow
3	Adjacent to cloud
4	Snow
5	Water
6	Unused
7	Unused

For Landsat 8 and 9, aerosol retrieval information that may have impacted the product is provided in a SR_Aerosol_QA band. The default “Aerosol Level” is Climatology (00), which means no aerosol correction was applied. Pixels with an “Aerosol Level” classified as high are not recommended for use.

Table 7: Landsat 8 and Landsat 9 aerosol level (SR_Aerosol_QA) bit index.

Bit	Flag	Description Values
0	Fill	0 Pixel is not fill; 1 Pixel is fill
1	Valid aerosol retrieval	0 Pixel retrieval is not valid; 1 Pixel retrieval is valid
2	Water	0 Pixel is not water; 1 Pixel is water
3	Unused	0
4	Unused	0
5	Interpolated Aerosol	0 Pixel is not aerosol interpolated; 1 Pixel is aerosol interpolated
6-7	Aerosol Level	00 Climatology; 01 Low; 10 Medium; 11 High

Processing

Landsat Collection 2 Level-2 products are processed by the USGS from Collection 2 Level-1 inputs. Landsat 8-9 OLI surface reflectance products are generated using the Land Surface Reflectance Code (LaSRC) algorithm. Landsat 4-5 TM and Landsat 7 ETM+ surface reflectance products are generated using the Landsat Ecosystem Disturbance Adaptive Processing System (LEDAPS) algorithm.

Media and example images

Figure 1: Landsat false color composites (highlighting vegetation) over an area in Tripoli District, Libya, showing changes between selected dates from 1984 to 2021.

Related services

• Water Observations from Space

• GeoMAD cloud-free composite services

• Landsat Collection 2 Level-2 Surface Temperature

References

• USGS Collection Level-2 website

• Landsat 8-9 OLI/TIRS Collection 2 Level-2

• Landsat 7 ETM+ Collection 2 Level-2

• Landsat 4-5 TM Collection 2 Level-2

License

There are no restrictions on Landsat data downloaded from the USGS; it can be used or redistributed as desired. USGS request that you include a statement of the data source when citing, copying, or reprinting USGS Landsat data or images.

Acknowledgements

Landsat Level- 2 Surface Reflectance Science Product courtesy of the U.S. Geological Survey.

Data access

Amazon Web Services S3

Landsat Collection 2 Level-2 is available in AWS S3, sponsored by the Public Dataset Program.

Table 8: AWS data access details.

AWS S3 details
Bucket ARD	arn:aws:s3:::deafrica-landsat
Region	af-south-1

The bucket is in the AWS region af-south-1 (Cape Town). Additional region specifications can be applied as follows:

aws s3 ls --region=af-south-1 s3://deafrica-landsat/

The file paths follow the format collection02/level-2/standard/<sensor>/<year>/<path>/<row>/<scene_id>/.

Table 9: AWS file path convention.

File path element	Description	Example
sensor	Landsat sensor name, tm, etm or oli-tirs for landsat 5, 7 and 8/9	oli-tirs
year	Observation year	2021
path	Landsat orbit path id	172
row	Landsat orbit row id	057
scene_id	Landsat scene id	LC08_L2SP_172057_20210101_20210308_02_T1

OGC Web Services (OWS)

This product is available through DE Africa’s OWS.

Table 10: OWS data access details.

OWS details
Name	DE Africa Services
Web Map Services (WMS) URL	https://ows.digitalearth.africa/wms?version=1.3.0
Web Coverage Service (WCS) URL	https://ows.digitalearth.africa/wcs?version=2.1.0
Layer name	ls5_sr, ls7_sr, ls8_sr, ls9_sr

Digital Earth Africa OWS details can be found at https://ows.digitalearth.africa/.

For instructions on how to connect to OWS, see this tutorial.

Open Data Cube (ODC)

The Landsat Collection 2 Level-2 products can be accessed through the Digital Earth Africa ODC API, which is available through the Digital Earth Africa Sandbox.

ODC product names: ls5_sr, ls7_sr, ls8_sr, ls9_sr

Specific bands of data can be called by using either the default names or any of a band’s alternative names, as listed in the table below. ODC Datacube.load commands without specified bands will load all bands.

Table 11: Landsat 5 and Landsat 7 Level-2 Surface Reflectance (ODC product ls5_sr and ls7_sr) band names.

Band name	Alternative names	Fill value
SR_B1	band_1, blue	0
SR_B2	band_2, green	0
SR_B3	band_3, red	0
SR_B4	band_4, nir	0
SR_B5	band_5, swir_1	0
SR_B7	band_7, swir_2	0
QA_PIXEL	pq, pixel_quality	1
QA_RADSAT	radsat, radiometric_saturation	0
SR_ATMOS_OPACITY	atmos_opacity	-9999
SR_CLOUD_QA	cloud_qa	0

Table 12: Landsat 8 and Landsat 9 Level-2 Surface Reflectance (ODC product ls8_sr and ls9_sr) band names.

Band name	Alternative names	Fill value
SR_B1	band_1, coastal_aerosol	0
SR_B2	band_2, blue	0
SR_B3	band_3, green	0
SR_B4	band_4, red	0
SR_B5	band_5, nir	0
SR_B6	band_6, swir_1	0
SR_B7	band_7, swir_2	0
QA_PIXEL	pq, pixel_quality	1
QA_RADSAT	radsat, radiometric_saturation	0
SR_QA_AEROSOL	qa_aerosol, aerosol_qa	1

Band names are case-sensitive.

For examples on how to use the ODC API, see the DE Africa example notebook repository.

Technical information

Surface Reflectance

The surface reflectance products for Landat 5, 7, 8, and 9 are generated using two different methods.

Landsat 5 TM and Landsat 7 ETM+ Collection 2 Surface Reflectance are generated using the Landsat Ecosystem Disturbance Adaptive Processing System (LEDAPS) algorithm. The software applies Moderate Resolution Imaging Spectroradiometer (MODIS) atmospheric correction routines to Level-1 data products. Water vapor, ozone, atmospheric height, aerosol optical thickness, and digital elevation are input with Landsat data to the Second Simulation of a Satellite Signal in the Solar Spectrum (6S) radiative transfer models to generate top of atmosphere (TOA) reflectance, surface reflectance, TOA brightness temperature, and masks for clouds, cloud shadows, adjacent clouds, land, and water.

Landsat 8 and Landsat 9 OLI Collection 2 Surface Reflectance data are generated using the Land Surface Reflectance Code (LaSRC), which makes use of the coastal aerosol band to perform aerosol inversion tests, uses auxiliary climate data from MODIS, and a unique radiative transfer model.

For more information on the different processing algorithms and caveats of the products, visit the Landsat Collection 2 Surface Reflectance webpage.