Landsat Bands

Each Landsat image is composed of one or more bands. A band is a range of wavelengths in the electromagnetic spectrum, that is depicted as grayscale in an image. Landsat bands span from the blue portion of the visible spectrum, towards the red portion of the visible spectrum, towards the near and mid infrared bands.

The following table illustrates the nine bands that are acquired by the Landsat 7 satellite:

An image with a single band is known as a monochromatic image, which appears in grayscale when accessed in imaging software. An image can contain more than one band; such an image is known as a composite image. Composite images that contain the bands from the visible part of the electromagnetic spectrum (red, green, and blue) are known as a true-color composite image. All other composite images are then known as false-color composite images.

CalView Landsat composite images come as either b321 (true color) or b457 (false color). The true color composite image makes use of bands 30, 20, 10, whereas the false color composite image makes use of bands 40, 50, and 70.

As mentioned before, each Landsat image is uniquely identified by its Path/Row identifier, and the exact date when the image is acquired. A system known as the Worldwide Reference System, or WRS, is used to identify the bounding boxes of the images captured by the Landsat satellite. Based on the WRS, each scene is identified by two values, the Path and the Row. For instance, the Landsat scene containing the San Francisco Bay Area has a path value of 44, and a row value of 34. In our services, we concatenate the two values, with a '0' separating them, to identify the scene, so the example would have a Path/Row value of 44034 in the mapping service. For filenames, we just concatenate the two values, so a file with a path value of 44 and a row value of 34 will contain 044034 (see below).

The combination of the Path/Row identifier, the acquisition date, and the band(s) contained by the image uniquely identify a particular image. For example, in the case of the following image file:

l7_04403420010930b457.tif

this filename indicates that the scene is acquired from Path/Row 44034, acquired on 20010930. The image file contains three bands, from bands 40, 50, and 70.

What kinds of information can be revealed by analyzing these bands? The next page explains. Landsat Band Applications