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PostGIS (/ ˈ p oʊ s t dʒ ɪ s / POST-jis) is an open source software program that adds support for geographic objects to the PostgreSQL object-relational database. PostGIS follows the Simple Features for SQL specification from the Open Geospatial Consortium (OGC). PostGIS is implemented as a PostgreSQL external extension. [2]
Refraction at interface. Many materials have a well-characterized refractive index, but these indices often depend strongly upon the frequency of light, causing optical dispersion. Standard refractive index measurements are taken at the "yellow doublet" sodium D line, with a wavelength (λ) of 589 nanometers.
uDig is a GIS software program produced by a community led by Canadian-based consulting company Refractions Research. [1] uDig is based on the Eclipse platform and features full layered Open Source GIS. It is written in Java and released under EPL and BSD licences (formerly under GNU LGPL). [2]
A BBB-accredited company agrees to abide by a set of accreditation standards BBB says are "attributes of a better business." These include honesty in advertising, transparency, and responsiveness ...
Manufacturers of optical glass in general define principal index of refraction at yellow spectral line of helium (587.56 nm) and alternatively at a green spectral line of mercury (546.07 nm), called d and e lines respectively. Abbe number is defined for both and denoted V d and V e. The spectral data provided by glass manufacturers is also ...
Snell's law (also known as the Snell–Descartes law, the ibn-Sahl law, [1] and the law of refraction) is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water, glass, or air.
The B in BK7 indicates that it is a borosilicate glass composition. BAK-4 barium crown glass (glass code 569560) has a higher index of refraction than BK7, and is used for prisms in high-end binoculars. In that application, it gives better image quality and a round exit pupil. An achromatic doublet, which combines crown glass and flint glass.
A negative-index metamaterial causes light to refract, or bend, differently than in more common positive-index materials such as glass lenses.. Negative-index metamaterial or negative-index material (NIM) is a metamaterial whose refractive index for an electromagnetic wave has a negative value over some frequency range.