The resolution of Band 8 (panchromatic) is 15 metres. Scientists call these “atmospheric windows” for specific wavelengths, and often satellite sensors are tuned to measure light through these windows. Urban areas are purple. Landsat numbers its red, green, and blue sensors as 4, 3, and 2, so when we combine them we get a true-color image such as this one: The signal is so strong that green often dominates the scene. In our photo-saturated world, it’s natural to think of the images on NASA’s Earth Observatory website as snapshots from space. Water is lighter in the blue band than it is in either the red or green bands, though the lake is too deep for shallow features to be visible. More about Landsat 7 band combinations Each range is called a band, and Landsat 8 has 11 bands. This helps distinguish water from snow and ice; it also distinguishes clouds made up mostly of liquid water or ice crystals. The result looks like the world as humans see it. Some methods are active, bouncing light or radio waves off Earth and measuring the energy returned; light detection and ranging (LiDAR) and radar technology are good examples. The brighter the red, the healthier the vegetation. SWIR (red), NIR (green) and green (blue), which is a combination often used to show floods or newly burned land. Water absorbs SWIR light in three regions: 1,400, 1,900 and 2,400 nanometers. In this case, plants reflect NIR and green light and absorb red. Color Infrared (5, 4, 3) This band combination is also called the near-infrared (NIR) composite. To understand what they mean, it’s necessary to understand exactly what a satellite image is. Though water vapor makes up just 1-4 percent of the atmosphere, it is an important greenhouse gas. The colder an object is, the longer the peak wavelength it emits. Water absorbs all three wavelengths, so it is black in this band combination. It all depends on the process used to transform satellite measurements into images. All light travels at the same speed, but the waves aren’t all the same. Infrared light reveals details of the evolving lava flows on Russia’s Tolbachik Volcano. Every surface or object absorbs, emits and reflects light uniquely depending on its chemical makeup. Data visualizers and remote sensing scientists make true- or false-color images to show the features in which they’re most interested, and they select the wavelength bands most likely to highlight those features. A combination of blue and SWIR light contrasts clouds, snow and ice in a large winter storm over the Great Lakes in January 2014. These colors are similar to what you would see from an airplane. For example, floods are best viewed in SWIR, NIR and green light because muddy water blends with brown land in a natural-color image. As a result, the colors in the final image may not be what you expect them to be. You can also explore false-color imagery with Landsat. As shown in the Great Lakes image below, this band combination is especially valuable in distinguishing snow, ice and clouds. Hence, blue bands are useful for seeing water surface features and for spotting the floor of shallow water bodies. Such false-color band combinations reveal unique aspects of the land or sky that might not be visible otherwise. In the current version of the VANE Language, we use images from the Landsat 8 satellite, which captures the Earth’s entire surface every 16 days. A photograph is made when light is focused and captured on a light-sensitive surface such as film or a charge-coupled device in a digital camera. This band combination is convenient for monitoring agricultural crops, which are displayed in bright green. Green islands punctuate the wetlands, which are black and blue. In this false-color band combination, plant-covered land is bright green, water is black and bare earth ranges from tan to pink. http://owm.io/sql-viewer?lat=44.4949&lon=1.1175&zoom=13&select=b4,b3,b2&op=rgb&from=l8&tabActive=2, http://owm.io/sql-viewer?lat=21.11&lon=-11.39&zoom=9&where=day%3E2016-09-01,day%3C2016-09-10&select=b4,b3,b2&op=rgb&from=l8&tabActive=1. It is also the basis for clouds and rainfall. Water is black and blue, and urban areas are silver. Saturated soil also will appear blue. But most aren’t. Finally, its coastal aerosol (B1) and cirrus band (B10) have a 60 meter pixel size. Like Earth’s surfaces, gases in the atmosphere also have unique spectral signatures, absorbing some wavelengths of electromagnetic radiation and emitting others. These observations can be turned into data-based maps that measure everything from plant growth or cloudiness. SWIR light includes wavelengths between 1,100 and 3,000 nanometers. In Figure 4 you will see several commonly used band combinations with a brief explanation on why it is used. The hotter an object is, the shorter the peak wavelength it emits. Images from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and from the early Landsats often are shown in this band combination because that’s what the instruments measured. In these images, it is possible to pick out different types of vegetation. Receive our FREE publication and weekly e-mail newsletter. Cities and exposed ground are gray or tan, and clear water is black. Let’s look at image #1 in the 5-4-3 band combination. A natural or true-color image combines actual measurements of red, green and blue light. When we see a photo where the colors are brightened or altered, we think of it as artful (at best) or manipulated (at worst). 3,2,1 The "natural color" band combination. SWIR bands are also useful for distinguishing between cloud types (water clouds vs. ice clouds) and between clouds, snow and ice—all of which appear white in visible light. Experiment with Different Band Combinations. Streambeds and the wetland in the upper left corner are darker than the surrounding arid landscape because of their water content. Color Infrared (B8, B4, B3) The color infrared band combination is meant to emphasize healthy and unhealthy vegetation. More information here! This TM band combination gives results similar to traditional color infrared aerial photography. Infrared light is not visible to the human eye/brain system, therefore no infrared light is perceivable as "color", or even "monochrome" to the human eye. It uses near-infrared (5), red (4), and green (3). Let’s look at image #1 in the 5-4-3 band combination. MIR energy also is useful in measuring sea-surface temperature, clouds and fires. This means SWIR measurements can help scientists estimate how much water is present in plants and soil.