The United States Geological Survey (USGS) in cooperation with NASA has developed a new Level 1G systematic (geometrically and radiometrically corrected) stitched data product from the Earth Observing-1 (EO-1) Advanced Land Imager (ALI).

The new ALI product represents an effort to increase the quality and usability of the current ALI data products available from EO-1. The previously available ALI image product was limited to radiometrically corrected (Level 1R) data with no geometric correction or georeferencing applied. The Level 1R image was provided in four separate files, or "strips," each of which corresponded to one of the sensor's four individual sensor chip assemblies. Each band within the new Level 1Gs product will be geometrically corrected and assemblies will be stitched together to provide a single mosaicked image file.

ALI is a 30-meter multispectral sensor with spectral band ranges and spatial resolutions very similar to the Landsat 7 Mapper Plus (ETM+). The L1Gs ALI product will include nine 30-meter bands in the VNIR and SWIR ranges and a 10-meter panchromatic band.

The standard ALI Level 1Gs processing includes improved radiometric calibration, geometric correction using satellite ephemeris information, and stitching of the image data from each of the four individual sensor chip assemblies into a single band file. The data will be georeferenced to the Universal Transverse Mercator (UTM) projection using the WGS84 datum, and the Level 1Gs product will be distributed on DVD or FTP in either GeoTIFF or HDF (4.1r5) format.

The new ALI product is available for $500 per scene, and may be searched and ordered through Earth Explorer ( or the USGS Global Visualization Viewer (

As the EO-1 Extended Mission continues its operations, the USGS and NASA are planning to develop additional products, including a Level 1G ortho-rectified ALI product as well as a possible Level 1G Hyperion product. The EO-1 website will provide further information about these products as they become available.

For more information on EO-1 and EO-1 data products, please visit the EO-1 website:

Source: USGS, Jan. 14, 2005