EarthSat GeoCover Project

The contract was part of the NASA Scientific Data Purchase which was administrated through NASA's Stennis Space Center in Mississippi.

There are two separate product lines developed from the GeoCover Project:

1. EarthSat GeoCover-Ortho (Orthorectified) products are the actual satellite images derived from Landsat TM scenes and are the most accurate, commercially available base maps of the world.
2. EarthSat GeoCover-LC (Land Cover) products consist of a medium resolution land cover database, prepared from consistently orthorectified Landsat Thematic Mapper (TM) imagery.

What follows next is a historical look at how the GeoCover Project was born:

Landsat Remote Sensing Satellite

Landsat 7 Launch

In July of 1972 NASA launched the first Landsat Earth remote sensing satellite, then called ERTS - Earth Resources Technology Satellite. Since 1972, six Landsat satellites have been placed into orbit. The latest (Landsat-7) was launched in April of 1999.

The Landsat satellites orbit the Earth at an altitude of over 900 kilometers. Using a sophisticated imaging scanner, Landsat collects digital imagery of the Earth's surface in multiple spectral bands at an approximate spatial resolution of 30 meters. Click here for more information about the Landsat satellite system.

Landsat digital imagery has long held the promise of providing a geodetically accurate image map of the Earth. With the advent of EarthSat GeoCover-Ortho, that promise has become a reality.

The Landsat imagery used to create the GeoCover-Ortho products have been hand selected to provide the lowest cloud cover and highest quality data possible. The Landsat TM imagery are all circa 1990 and have been selected as close to the local peak growing season as possible. The imagery have been collected from the majority of the Landsat foreign ground stations, as well as from the US Government's EROS Data Center. Never before has such a complete collection of high quality Landsat imagery been assembled for processing and analysis. The GeoCover-Ortho image map data sets represents a milestone in the use of Landsat digital imagery to map and study the Earth's surface.

Building Image Maps From Landsat Imagery

The science of creating positionally accurate image maps from digital Landsat imagery is termed "softcopy Landsat photogrammetry". The Landsat photogrammetric process is computationally intensive and has only been economically feasible with the advent of high speed computers and specially designed photogrammetric software. Unlike other approaches to Landsat photogrammetry, which require an extensive amount of control, MDA employs a proprietary, patented technique to perform a simultaneous block adjustment of groups of up to 400 Landsat scenes with less than 10% of those scenes containing ground control.

GeoCover-Ortho Custom Mosaic of Cyprus

MDA's Landsat photogrammetric approach combines the world's best available horizontal and vertical control with detailed manually measured tie points between adjacent imagery to create a highly accurate spatial relationship between the raw Landsat imagery and the surface of the Earth.

Using high speed computers, this relationship is used to correct the geometry of the raw Landsat imagery so that it creates a detailed map with a positional accuracy of 50 meters RMS.

The combination of the highly accurate control (both positional and elevation control) and the unique capabilities of MDA's patented photogrammetric software imparts on the GeoCover-Ortho image products a geodetic positional accuracy that is better than the vast majority of the world's 1:200,000 scale maps.

EarthSat GeoCover-Ortho Image Products

The GeoCover-Ortho image products are available from MDA both as digital image files and as full color photographic prints.

Two suites of products are available:

• Stock - The stock suite are "off-the-shelf" products providing an extremely rapid turnaround at an very affordable price.
• Custom - The custom suite are tailored to the individual customer needs, allowing the customer to specify the projection, datum, and, in the case of mosaics and photographic prints, the three spectral band to use for the color composite image.

In both the Stock and Custom Suites, the digital data are available either as single Landsat TM scenes or digitally combined mosaics:

• GeoCover-Ortho Single Scenes - A single Landsat scene covers an area of approximately 170x170 kilometers. The data set is comprised of all seven Landsat spectral bands. Stock Scenes are available in a UTM projection, and Custom Scenes are available in any customer selected projection and/or datum.
• GeoCover-Ortho Mosaics - Landsat mosaics are created by digitally suturing a group of juxtaposed Landsat scenes into a single seamless digital image. Mosaics are color (3 band) products. Stock Mosaics use Landsat spectral bands 7,4,2 as red, green, blue respectively; Custom Mosaics are constructed from any three customer selected spectral bands.

EarthSat GeoCover-LC Image Products

GeoCover LC data are available in the following formats:

• Vectors as ARC/INFO coverages
• Rasters as ERDAS IMAGINETM 8.4 files:
• 13 class raster cells
• Land-water raster cells
• 13 class full-TM scene with MMU
• 13 class full-TM scene, full-resolution
• Polygon Vector Coverage
• Pre-clustered categorized raster data, 240 spectral classes, separated by a combination of unsupervised and supervised classification algorithms.
• GeoCover LC data are available on CD-ROM, or on 4- or 8-mm tape