Twenty-five percent of the earth’s surface is covered in varying degrees of vegetation (the other 75% being oceanic). The NASA/NOAA Suomi NPP (National Polar-orbiting Partnership) satellite carries the VIIRS (Visible-Infrared Imager/Radiometer Suite) sensor which is able to collect remote sensing data about the intensity of the earth’s vegetation. VIIRS is able to sense changes in the reflection of light and can be used to measure changes in vegetation over time. (Previously, NASA released imagery from the the Sumoi NPP that captured views of the earth at night).
Satellite images collected over the course of a year from April 2012 to April 2013 were used to stitch together a global map showing the intensity of vegetation around the world. An enormous amount of data collection went into creating this map of the earth’s vegetation. According to NOAA, “330 megabytes of data every minute just for the four channels of visible and near-infrared imagery used in the vegetation index.” More than 2 terrabytes of data is collected by VIIRS each week just for those channels (additional data is collected by VIIRS in 17 other channels). Furthermore, “At 500 meters per pixel, the images that the data generates are equally large. Each weekly colorized vegetation image is around 13 gigabytes in size and 80,000 x 40,000 pixels in dimension.”
On the map, the darker the green, the more lush the vegetation. The paler, sand colored areas represent landscapes low or absent in vegetation due to snow, drought, rock, or urban areas. The data will be incorporated into Normalized Difference Vegetation Index, or NDVI-based data and services. Vegetation data has been collected for the past 22 years by NOAA with its AVHRR sensor and since 1999 by NASA with its MODIS sensor. The new data from VIIRS marks an improvement in the quality and detail of the vegetation data. The data from VIIRS is eight times more detailed than NOAA’s AVHRR sensor on its POES polar-orbiting satellite. VIIRS also doesn’t have the blurring of imagery that occurs with NASA’s MODIS sensor the further away from center of the orbit swath.
