Image indices are images that are computed from multiband images. The images emphasize a specific phenomenon that is present, while mitigating other factors that degrade the effects in the image. For instance, a vegetation index will show healthy vegetation as bright in the index image, while unhealthy vegetation has lower values and barren terrain is dark. Since shading from terrain variation hills and valleys affect the intensity of images, the indices are created in ways that the color of an object is emphasized rather than the intensity or brightness of the object. The value of a vegetation index for a healthy pine tree that is shadowed in a valley will have a similar value as a pine tree that is in full sunlight. These indices are often built by combinations of adding and subtracting bands, thereby making various band ratios. They are tied to specific bands that are in specific parts of the electromagnetic spectrum. As a result, they may only be valid for certain sensors or classes of sensors and it is critical that the proper bands are used in the calculation. One of the common ways that these indices are used is for comparison of the same object across multiple images over time.
Vegetation and soils indices
Torso in a Yellow Shirt (Complicated Premonition)
This article was published more than 3 years ago. Some information may no longer be current. In response to the nerve-agent attack on a former Russian spy and his daughter in the United Kingdom earlier this month, Canada is expelling four Russian diplomats and denying three applications from the Russian government for additional diplomatic staff.
Water indices
World of Dreamings Traditional and modern art of Australia. Emily Kam Kngwarray is regarded as a phenomenon in Australian art. For an elderly, traditional Aboriginal woman who, it was popularly believed, started painting in her seventies, she worked with immense speed and assurance.
The graphic trace in art is explored here in relation to the index and the diagram through the work of several modern and contemporary artists. The index and the diagram are two seemingly incompatible types of sign. While the index has a close, causal or tactile connection with the object it signifies, the diagram is a form of representation that often involves statistical abstraction from phenomena, such as trends in the stock market or the weather. Graphs and diagrams convert statistical data into lines, bars or pie-charts; or translate temporal relations into spatial relations. Some forms of diagrammatic representation, however, are generated directly by their object. These beats and tremors are registered on a graph showing variations over time as a spiky line. It is this hybrid form of representation — this indexical diagram — that will henceforth be referred to as a graphic trace.
