Jointly managed by NASA and US Geological Survey
The Landsat program, started in 1972, is one of the mainstays of NASA's earth-observation program. Entering orbit on February 11, 2013 LDCM (Landsat 8) was the first satellite of the Landsat family launched since April 15, 1999. With the decommissioning Landsat 5 on June 5, 2013 and the 2003 the Scan Line Corrector (SLC) failure of Landsat 7, Landsat 8 is the only fully operational Landsat satellite in orbit.
The Landsat satellites were designed to be of use to a variety of fields like forestry, agriculture, geology, and land-use planning, and the choice of spectral bands for the Landsat satellites was geared toward discriminating different types and amounts of vegetation. Landsat's strengths are generally seen to be its regular acquisition schedule (revisits each spot on the earth every 16 days), long-term data archive (image with comparable specifications is available from 1982), and relatively rich spectral information (not as rich as hyperspectral data, but more bands than most high-resolution satellites like Ikonos or Quickbird).
Limitations of Landsat data include its moderate spatial resolution (30m multispectral data, 15m panchromatic), and the fixed acquisition schedule that makes it difficult to acquire imagery for a particular place at a particular time (especially if clouds or smoke occur frequently over the area of interest).
Landsat 8 carries two push-broom instruments: the Operational Land Imager (OLI), and the Thermal Infrared Sensor (TIRS).
The spectral bands (1 - 9) of the OLI sensor, while similar to Landsat 7’s ETM+ sensor, provide enhancement from prior Landsat instruments, with the addition of two new spectral bands: a deep blue visible channel (band 1) specifically designed for water resources and coastal zone investigation, and a new infrared channel (band 9) for the detection of cirrus clouds. A new Quality Assurance band is also included with each data product. This provides information on the presence of features such as clouds, water, and snow.
|Comparison of Landsat 8 Bands to Earlier Landsat Bands|
|Description||Landsat 5 & 7 Bands||Landsat 8 Bands|
The Thermal Infrared Sensor (TIRS) contains two thermal bands (10 and 11), which measure land surface temperature at 100-meter resolution. (The product provided is resampled and delivered as a 30-meter image). In the TIRS thermal bands, dark pixels represent cool temperatures; light pixels represent hot temperatures. Thermal band data provide important information about water irrigation use in arid land, as well as heat units in urban areas.
Landsat 8 imagery has a radiometric resolution of 12-bits (16-bits when processed into Level-1 data products) compared to 8-bits for its predecessor.
Landsat 8 has 11 bands with imagery available at varying resolutions:
|1||30m||0.433 - 0.453||Coastal/Aerosol||Operational Land Imager (OLI)|
|2||30m||0.450 – 0.515||Blue||OLI|
|3||30m||0.525 – 0.600||Green||OLI|
|4||30m||0.630 – 0.680||Red||OLI|
|5||30m||0.845 – 0.885||Near Infrared||OLI|
|6||60m||1.560 – 1.660||Short-wave Infrared||OLI|
|7||30m||2.100 – 2.300||Short-wave Infrared||OLI|
|8||15m||1.360 – 1.390||Panchromatic||OLI|
|9||30m||0.52 - 0.90||Cirrus||OLI|
|10||100m||10.6 - 11.19||Thermal Infrared||Thermal Infrared Sensor (TIRS)|
|11||100m||11.5 - 12.51||Thermal Infrared||TIRS|
Natural color (bands 4,3,2) images of Gilbert, Arizona
The “before” image (left) is a false-color Landsat 8 image acquired May 28, 2013. The “during” image was acquired, June 13, 2013, while the New Mexico Silver Fire was still growing. (The white puffs with black shadows in the right image are clouds.)
Full scene from Thermal Infrared Sensor (TIRS) Band 10
To ensure data continuity with previous Landsat datasets, Landsat 8 imagery is delivered in scenes that measure 115mi (185km ) by 106mi (170km).
Landsat 8 orbits the earth every 16 days. Landsat 8 follows the WRS-2 position previously used by Landsat 5. This provides 8-day coverage when coupled with Landsat 7 data. An acquisition calendar is available at http://landsat.usgs.gov/tools_acq.php.
Landsat Data Continuity Mission imagery became available starting on April 11, 2013. Landsat Data Continuity Mission imagery is available at no cost. The following sources contain Landsat 8 imagery available for download: the USGS Global Visualization Viewer GLOVIS or the USGS Earth Explorer.
The TIRS captures data in two long-wave thermal bands with a minimum of 100-meter resolution, but is registered and delivered with the OLI data product. Through USGS users can also acquire LDCM TIRS imagery resampled to 30-meter resolution to match the spatial resolution of the OLI sensor multispectral bands.
Images are delivered as .tar.gz compressed files (approximately 1 GB) which are unzipped as GeoTIFF files (approximately 2 GB).
Landsat imagery is one of the most ubiquitous satellite image types, and a lot of effort has gone into making it easy to access and use. For the most part, Landsat imagery can be used in ArcGIS or other GIS applications without any special processing. Most Landsat images obtained either through USGS or another provider are distributed in GeoTIFF image format with one band per file. For the purposes of making it easier to handle, manipulate, and display the imagery, most people combine all of the separate image bands into a single, multi-band image file using an image-processing package like ENVI or ERDAS Imagine.
Landsat images are not terribly big or difficult to process by today's computing standards. In a GeoTIFF image format, the file for a single 30m band is approximately 53MB. As long as you are dealing with a study area that is contained within one or a few Landsat scenes, you should not need any special computer hardware to be able to use Landsat imagery.
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