Landsat Analysis Ready Data (GLAD ARD) and GLAD Tools

GLAD Landsat ARD Tools

 

The Landsat Analysis Ready Data (ARD) created by the Global Land Analysis and Discovery team (GLAD) serves as a spatially and temporally consistent input for land cover mapping and change detection at global to local scales. The GLAD ARD represents a 16-day time series of globally consistent, tiled Landsat normalized surface reflectance from 1997 to the present operationally updated every 16 days. Accessible through a dedicated Application Programming Interface (API) without any associated charges, the GLAD ARD imposes no restrictions on subsequent redistribution or use, provided proper citation is given following the Creative Commons Attribution License (CC BY).

 

In addition to the ARD dataset, the GLAD team has developed the GLAD Tools software suite. This suite enables users to apply time-series data processing, spectral and temporal data analysis, and machine-learning characterization to the GLAD ARD. The GLAD Tools User’s Manual supports users in applying the latest version of the software for national and regional land cover characterization, change assessment, and area reporting, incorporating state-of-the-art mapping and sample analysis techniques. Together, the global GLAD ARD and GLAD Tools provide an end-to-end solution for no-cost Landsat-based natural resource assessment and monitoring at national to global scales.

 

GLAD ARD Data Format

The GLAD ARD represents a 16-day time series of globally consistent, tiled Landsat normalized surface reflectance and brightness temperature. Within each 16-day interval, the GLAD ARD preserves Landsat observations with minimal cloud and shadow contamination. These data composites are stored as 8-band, 16-bit unsigned, LZW-compressed GeoTIFF files, in geographic coordinates, featuring a spatial resolution of 0.00025 degrees per pixel, equivalent to 27.83 meters per pixel at the Equator. The product utilizes the World Geodetic System WGS84 (EPSG:4326)

 

The global Landsat ARD product is organized into 1x1 geographic degrees tiles, each comprising 4004x4004 pixels, with a 2-pixel overlap. Tile nomenclature is derived from the tile center's integer value in degrees. The global GLAD ARD tile database is accessible online. Landsat image data collected in a 16-day interval are consolidated into a single ARD composite. A year encompasses 23 composites (GeoTIFF files), each assigned a unique numeric ID starting from the first composite in 1980. The 16-day interval ID table is available online.

 

In 2022, the GLAD team updated the ARD product using Landsat Collection 2 data. Collection 2 offers enhanced geometric accuracy and radiometric calibration compared to Collection 1 products. The entire ARD dataset from 1997 to the present has undergone this update, resulting in the decommissioning of the ARD Collection 1-based product.

 

GLAD ARD Data Access

The global Landsat ARD is available for download using dedicated ARI which provides access to 16-day tiled composites (GeoTIFF files). A user must select tiles and 16-day intervals for ARD download from the global metadata. The GLAD Tools software includes tools for automated ARD data download. See GLAD Tools User’s Manual for data download and organization instructions.

 

To access an individual 16-day composite from GLAD cloud storage, a user may implement API commands in cURL or Wget command-line utilities.

 

Example of API data download command for a single ARD tile (105E_13N) and single interval (920):

curl -u <username>:<password> -X GET https://glad.umd.edu/dataset/glad_ard2/<lat>/<tile>/<interval>.tif -o <outfolder>/<interval>.tif
  • <username> and <password> - the default API credentials are: Username: glad; Password: ardpas.
  • <tile> - the ARD tile name.
  • <lat> - tile latitude, the second half of the ARD tile name (e.g., for the 105E_13N, is 13N).
  • <interval> - the 16-day interval ID (e.g., 920).
  • <outfolder> - output path.

Alternatively, GLAD ARD can be accessed from the Amazon Web Services (AWS) S3 cloud storage. Presently, only a portion of the global ARD data is available on AWS S3. New data may be added upon request to Peter Potapov. ARD data on AWS S3 is provided as public access and is free to download or use in the cloud. The path to the ARD data from S3 is:

/vsis3/glad.landsat.ard/data/tiles/<lat>/<tile>/<interval>.tif

 

GLAD Tools

The GLAD Tools is a collection of freeware utilities that enable advanced ARD data analysis and land cover and land use change assessment, including:

  1. Landsat ARD Data Management: Facilitates the download and efficient management of Landsat Analysis Ready Data (ARD).
  2. Annual Image Composites: Enables the creation of cloud-free annual image composites and multitemporal metrics for land cover mapping and change detection.
  3. Supervised Land Cover Classification: Employs advanced machine learning tools for accurate supervised land cover classification and change detection.
  4. Map Analysis: Supports map analysis through image algebra modeling, focal analysis, and precise area calculation.
  5. Sample Reference Data Collection: Facilitates the collection of sample reference data and their analysis to estimate map accuracy, unbiased area, and area estimation uncertainty.

The combined capabilities of the global GLAD ARD and GLAD Tools offer a comprehensive, no-cost solution for national and regional users engaged in Landsat-based forest and land cover/land use monitoring. The GLAD Tools and ARD were successfully tested in many countries and regions and were adopted for forest and land cover monitoring at the national scale.

 

The distributed version of GLAD Tools is designed for Windows 10 and 11 operation systems. The minimum PC requirements are 8GB RAM and at least 50GB HDD space. The GLAD Tools are built using MinGW and GDAL software packages. The Tools require the user to install several open-access software packages (Strawberry Perl, QGIS/OSGeo4W, R, and Google Earth Desktop) before software installation. The GLAD Tools installation requires user to have administrative privileges on the Windows system. Please follow GLAD Tools installation instructions in the User’s Manual to set up the Tools.

 

The GLAD Tools are periodically updated. We recommend checking and updating GLAD Tools periodically. The user also needs to keep dependencies (listed in a text file within the software folder) up to date (in case a new version of QGIS or R software is installed).

 

The latest version of the GLAD Tools is available here.

 

GLAD Tools User's Manual

The GLAD Team prepared two versions of the User’s Manual. The short Quick Start Guide is the best way to start working with GLAD Tools. It includes instructions for most of the tools and guides a new user through Tools applications using templates provided with the software. The Quick Start Guide is available in the following languages:

A complete User’s Manual includes information on all GLAD Tools functions and provides a detailed reference for the ARD data processing and properties. This document is available only in English.

 

Dataset and Software License

The GLAD Landsat Analysis Ready Data (ARD) data is available online, with no charges for access and no restrictions on subsequent redistribution or use, as long as the proper citation is provided as specified by the Creative Commons Attribution License (CC BY).

 

The GLAD Tools available are with no charges and no restrictions on subsequent redistribution or use, if the proper citation is provided as specified by the Creative Commons Attribution License (CC BY).

 

Copyright © Global Land Analysis and Discovery Team, University of Maryland

 

Suggested citation:

Potapov, P., Hansen, M.C., Kommareddy, I., Kommareddy, A., Turubanova, S., Pickens, A., Adusei, B., Tyukavina A., and Ying, Q., 2020. Landsat analysis ready data for global land cover and land cover change mapping. Remote Sens. 2020, 12, 426; doi:10.3390/rs12030426

 

Disclaimer

While the GLAD team makes every effort to ensure the completeness and consistency of the Landsat ARD product, we acknowledge that it may contain faults and unreadable data. We ask that you notify us immediately of any problems with our data. We will make every effort to correct them.

 

Concerning the Landsat ARD data and GLAD Tools provided through this service, the GLAD team disclaims any warranties, whether express or implied, including but not limited to the warranties of merchantability and fitness for a particular purpose. Additionally, the team assumes no legal liability or responsibility for the accuracy, completeness, or usefulness of the data products.

 

While the GLAD team is dedicated to ongoing product updates and maintaining open data access, it is important to note that the continuity of this service is subject to the availability of adequate funding and resources. Consequently, interruptions or cancellations of this service may occur at any time without prior notice.

 

Contact

For all questions and comments please contact Peter Potapov