| Garland Vegetation Cover, 1975-2000
Remote sensing is defined as collecting information from a distance. The types of remote sensing we are most familiar with are satellite-based weather imaging systems that we see daily on the evening news. These particular systems can be credited with the saving of many lives as they are early warnings for deadly weather systems such as hurricanes. Remote sensing is not only from satellite-based systems though, radar and aerial photography are employed as remote sensing technologies as well.
But remote sensing is not new. As soon as an aerial platform was available, remote sensing was employed. The first military use of aerial photography was during the American Civil war, when still photographs of enemy fortifications were taken from captive balloons. The advent of the space-age and Earth-orbiting satellites provided even greater opportunities for the development and deployment of remote sensing systems for both military and civilian applications.
Today, in addition to weather satellites, numerous imaging systems are orbiting the Earth collecting data and helping scientists learn more about the world around us.
The particular dataset we are highlighting here is based on data collected from the satellite-based sensing systems of the Landsat program. Landsat is a series of satellites, the first of which launched in 1972. The Landsat satellite system collects information from a range of the electromagnetic spectrum both visible and invisible - referred to as “bands.” This wide range of spectra allows scientists to combine the different bands to see things that may not be obvious to the naked eye. In this case, by combining certain bands, researchers can clearly identify what is vegetation and filter out what is not.
Since the various Landsat satellites have been in orbit for up to 40 years, changes over time can be analyzed. Changes in vegetation cover, for example, are of particular interest to those concerned about the environment, particularly urban sprawl. The Normalized Difference Vegetation Index, or NDVI for short, is a standardized combination of certain bands that highlight vegetation. By viewing these data over time, changes in vegetation cover can be readily seen. This viewer will allow you to view any location on the Earth, Garland Texas included. Take a look, and see if you can determine if your neighborhood is greener… or not!
|
