User Manual - pancroma

8. Landsat 7 Data Sets________________________________________________________________The primary purpose of the Landsat earth survey satellites is to provide scientistswith data to assess the earth’s vegetation, crop and mineral resources. It wasnot necessarily intended to produce true color images of the earth’s surface.However, Landsat bands 3, 2, and 1 are close to the red, green and blue(respectively) wavelengths that the human eye is sensitive too. These bands canbe inserted into an RGB color model and will produce images that are verysatisfactory for visualization. Of course PANCROMA TM can also combine othersets of Landsat bands in order to produce false-color images for scientificpurposes. For example, bands 4, 3, 2 are commonly used to highlightvegetation. Many other combinations of bands are used for different purposes.A good reference describing Landsat band characteristics can be found athttp://web.pdx.edu/~emch/ip1/bandcombinations.html.The Landsat 7 platform is the Enhanced Thematic Mapper (plus) (ETM+). Thespecifications for its sensors are given below. (The bands highlighted in blue arethe most useful for producing natural color images.)Band Wavelength (µ) Resolution (m)1 0.450-0.515 (blue) 302 0.525-0.605 (green) 303 0.630-0.690 (red) 304 0.750-0.900 (near-IR) 305 1.55-1.75 (mid-IR) 306 10.4-12.5 (thermal-IR) 607 2.08-2.35 (long-IR) 30Panchromatic 0.52-0.90 (green-near IR) 15Among other improvements, ETM+ included for the first time a 15m resolutionpanchromatic band. Rather than detecting radiation in a narrow range offrequencies, a panchromatic sensor collects radiated energy across a broaderspectrum. In the case of Landsat, this spans the green, red and near infrared(NIR) frequencies. And it does so at increased resolution compared to previoussensors, i.e. 15m/pixel as opposed to the 30m/pixel resolution of the bandsensors.The panchromatic data is recorded in a single channel. So despite havinggreatly increased resolution compared to bands 1-7, the panchromatic band canstill only be displayed as a black and white image. The useful visible RGB colordata is stored separately in channels 3, 2, and 1, but of course at the lower (30m)resolution.14