The Global Land Survey (GLS) data sets were created as a collaboration between NASA and the USGS from 2009 through 2011. GLS datasets allowed scientists and data users to have access to a consistent, terrain corrected, coordinated collection of data.
Each of these collections were created using the primary Landsat sensor in use at the time for each collection epoch:
- GLS1975: Landsat 1-3 Multispectral Scanner (MSS), 1972-1983, (Landsat 4-5 MSS scenes from 1982-1987 were used to fill data gaps)
- GLS1990: Landsat 4-5 Thematic Mapper (TM), 1987-1997
- GLS2000: Landsat 7 Enhanced Thematic Mapper Plus (ETM+), 1999-2003
- GLS2005: Landsat 7 ETM+ and Landsat 5 TM, 2003-2008
GLS2010: uses a combination of Landsat 7 ETM+ and Landsat 5 TM, 2008-2012
The Landsat data incorporated into each GLS data set meets quality and cloud cover standards, and is processed to the following parameters:
- Data Resolution (Reflective bands): 30 meters (Landsat MSS: 60 meters)
- Data Format: GeoTIFF (Level-1 product), Full-resolution .jpg (LandsatLook images)
- Resampling: Cubic Convolution
- Projection: Universal Transverse Mercator (UTM)
The accuracy of the GLS2000 dataset is less than one pixel (25-meter root mean square error (RMSE) on a per image basis). This means that the image is accurate to 30 meters or less.
In this publication, USGS EROS scientists used image-to-image and triangulation block adjustment methodologies to compare higher resolution control data, as well as systematically processed Landsat 7 data, to compare against the GLS2000 dataset.
The GLS2000 dataset is the source of the Landsat ground control library. Ground Control Points (GCP) contained in the library are used to correct all Landsat images that are processed to standard terrain correction.