Landsat Collection 2 Level-2 Surface Reflectance

Date modified: 23 August 2021

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 and 8 satellites, including historical observations dating back to late 1980s and regularly updated new acquisitions.

New Level-2 Landsat 7 and Landsat 8 data are available after 15 to 27 days 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 for Land (CARD4L)-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.

Specifications

Spatial and temporal coverage

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

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

Satellite

Landsat 5

Landsat 7

Landsat 8

Instrument

Multispectral Scanner (MSS), Thematic Mapper (TM)

Enhanced Thematic Mapper (ETM+)

Operational Land Imager (OLI), Thermal Infrared Sensor (TIRS)

Number of bands

10

10

10

Cell size - X (metres)

30

30

30

Cell size - Y (metres)

30

30

30

Coordinate reference system

Universal Transverse Mercator (UTM)

UTM

UTM

Temporal resolution

Every 16 days

Every 16 days

Every 16 days

Temporal range

1984 – 2012

1999 – present

2013 – present

Parent dataset

Landsat Collection 2 Level-1

Landsat Collection 2 Level-1

Landsat Collection 2 Level-1

Update frequency

NA (archive)

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 Level-2 Surface Reflectance measurements

Landsat 8 Level-2 science product is generated using a different algorithm and has 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 for Landsat 5, 7 and 8 are generated by the CFMask algorithm. Different bit definitions are used because the cirrus band is only available on Landsat 8. 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

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 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

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, 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 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 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

Landsat composites for Libya

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

References

USGS Collection Level-2 website

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

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

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

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 Level-2 Surface Reflectance (ODC product ls8_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 and 8 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 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.