Tuesday, July 2, 2013

Landsat 8 data on Google Earth Engine

On February 11th 2013, NASA successfully launched Landsat 8, the latest in a series of Earth observation satellites that dates back to 1972.  On May 30th, the U.S. Geological Survey began making data from the satellite available to the public. Google Earth Engine started collecting the Landsat 8 data as soon as the USGS made it available, and has recently added it to their Landsat 8 catalog. In addition to the raw satellite data, Earth Engine provides access to 8-day, 32-day, and annual composites of Landsat 8 satellite data, as well as analyses highlighting vegetation, snow, water, and fire.  You can also view imagery from Landsat 7, Landsat 5, Landsat 4, and Landsats 1 - 3, bringing you all the way back to 1972.

Here's a recent image of the San Francisco Bay area:

Landsat 8's bands are named differently than those of the Landsat 5 and 7 satellites, they cover different wavelengths, and there are several new bands.  The USGS has a nice guide detailing the differences between Landsat 7 and Landsat 8.  Here is a brief description of each band.  For more information, please see the USGS Landsat 8 page and specifically their page on band designations.

B1:  A new band, useful for studying water and atmospheric aerosol concentrations
B2:  Blue
B3:  Green
B4:  Red
B5:  Near Infrared
B6:  Short wave infrared 1
B7:  Short wave infrared 2
B8:  Fifteen meter panchromatic band
B9:  A new band for detecting cirrus clouds
B10:  Thermal infrared 1
B11:  Thermal infrared 2
BQA:  A quality assessment band

Here are some examples of visualizations you can easily create using Earth Engine.  

Farms on the outskirts of Las Vegas, Nevada in "true color" - Bands 4, 3, 2, and then the same scene in "false color" - Bands 6, 5, 4.  This combination of bands turns areas with photosynthetic activity bright green.  For example, the farms in the lower left corner, and the golf course in the upper right corner.

To generate your own:

  • Switch to the Workspace tab (upper right, just above the map) and zoom in a few levels to an area you are interested in
  • Type "Landsat 8 Annual"  in the search box at the top, and choose the Landsat 8 Annual Greenest-Pixel TOA Reflectance Composite

To select different bands, click on the grey layer on the left hand side to get the visualization editing panel.  Pull the B4, B3, and B2 to different bands to see the effect.  See the USGS site on band combinations for more examples.  

In the past, Google and its partners have used Landsat data to create pannable, zoomable, timelapse images of the entire Earth over the last 29 years, the highest resolution imagery of forest in Mexico, high resolution maps of water in the Congo basin, and operational systems for monitoring deforestation. The data returned by Landsat 8 both continues the work of its predecessors, and adds several new types of information.  Welcome Landsat 8, and  congratulations to NASA and USGS for a successful launch!   To learn more about how to use Earth Engine, please read the Earth Engine tutorial.