 ASU |
 UTEP |
SWGEONET |  GEON |
 NSF |
 NASA |
SWGEONET Module 3-- Remote Sensing |
ASU |
UTEP |
SWGEONET | GEON |
NSF |
NASA |
SWGEONET Module 3-- Remote Sensing |
| A variety of remote sensing data obtained from ASTER (Advanced Spaceborne Thermal Emission and
Reflection Radiometer)imagery are available within the SWGEONET framework. The beauty of these images is that no
external software is required to make use of them (JPEG images); however, data output can be incorporated into
higher level GIS (Geographic Information Systems) applications (GeoTIFF). Descriptions of the four available products are nearly verbatim from the White Paper on ASTER Band Combinations by W.L. Stefanov. Additional details and information is contained within the paper. This data product is comprised of bands 3, 2, 1 as Red-Green-Blue (RGB) at 15 m/pixel spatial resolution. This band combination highlights actively photosynthesizing vegetation in red (near-infrared band), with undisturbed bedrock and soils primarily expressed as browns, greens, and greys. Built materials and regions typically exhibit blue-green, reddish - purple, and white colors. This data product is the result of ((band 3 – band 2)/(band 3 + band 2)) calculated for each image pixel in a given scene. The resulting greyscale image provides a relative abundance map of actively photosynthesizing vegetation at 15 m/pixel. Bright pixels correspond to higher relative vegetation abundance, while dark pixels correspond to lower vegetation abundance. These images comprise bands 8, 6, and 4 as RGB at 30 m/pixel. These bands have been selected primarily to highlight spectral features diagnostic for iron oxides, illite, and kaolinite (bands 8 and 6); and carbonates (band 4). This data product is designed for rapid reconnaissance based on these general mineral types; multispectral analysis using all six calibrated shortwave bands is recommended for detailed mineralogical investigations. Bands 13, 12, 10 as RGB at 90 m/pixel comprise this data product. These bands have been selected primarily to highlight spectral features diagnostic for silicates (band 13), iron- and magnesium-bearing minerals and lithologic types (band 10), and carbonates (all three bands). Using these band combinations, quartzites are bright red; basaltic rocks are blue; granitoids are purple-violet; and carbonates tend to be green to yellow-green. ExerciseBecause you cannot upload the image you just obtained into the viewer, some sample images for analysis are provided below. The following ASTER scenes were acquired over Arizona. The false color images are not available through SWGEONET-- they have been manipulated using ArcMap. Examine the image on the top left closely, and answer the following questions. Which areas have the most vegetation? Which areas have the least vegetation? Besides bare rock, what could account for unvegetated areas? What patterns are discernible at this scale? Examine the image on the top right and answer the following questions. Is it any easier to discern the vegetated areas from unvegetated areas with this color scheme and scale? Describe any differences in pattern between the gray scale and color version of the 2001 images. Describe how the gray scale and the false color differ from 2001 to 2003. What could have caused the difference in the vegetation patterns visible on each image? The red line separating the light and dark areas on the above images is the perimeter of the 2002 Rodeo-Chediski fires. These NDVIs are useful for working with burn severity (determining how badly a fire burned an area) and with vegetation regrowth after the fire, both of which play an important role in hazard identification. |
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