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Sci-Tech Dictionary:

square degree

(′skwer di′grē)

(mathematics) A unit of a solid angle equal to (π/180)2 steradian, or approximately 3.04617 × 10-4 steradian.

 
 
Measures and Units: square degree

solid angle. Symbols □° (°)2. The equivalent to the square of the ordinary planar degree, hence = ( π/180)2 steradian.

This simple-looking transformation is misleading, for the two degrees are in spatial dimensions 2 and 3 rather than 1 and 2, and the parameter π is not raised to a power for the steradians in a sphere. Since there are 4π steradians in the sphere, the square degree = π/129600 sphere.

 
Wikipedia: square degree

A square degree is a non-SI unit that can be used to measure solid angles (that is, the area of the projection of a surface onto a unit sphere centered on the point of observation). It is the two-dimensional equivalent of the degree and may be denoted "sq.deg.", "deg²", or a symbol of a square followed by °.

The number of square degrees in the whole sky (a sphere) is 4π(180/π)² = 129,600/π (that is, approximately 41,253 sq.deg.), which can be derived from that the fact that the whole sky covers 4π steradians, and one degree is π/180 radians. Thus, one square degree is approximately 1/3283 steradian or 305 microsteradians.

For example, observed from the surface of the Earth, the Moon has a diameter of approximately ½º, so it covers an area of approximately 0.2 sq.deg.


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Sci-Tech Dictionary. McGraw-Hill Dictionary of Scientific and Technical Terms. Copyright © 2003, 1994, 1989, 1984, 1978, 1976, 1974 by McGraw-Hill Companies, Inc. All rights reserved.  Read more
Measures and Units. A Dictionary of Weights, Measures, and Units. Copyright © Donald Fenna 2002, 2004. All rights reserved.  Read more
Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Square degree".  Read more

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  • square grade (solid angle)
  • Astronomical catalogs (astronomy)
  • symbols (mathematics, mathematics, sub-atomic physics, mass, sub-atomic physics, sub-atomic physics, electromagnetics, sub-atomic physics, mathematics, geology)
  • degree (length, plane angle, solid angle, mathematics, statistics, physics, hydrometry, viscometry, hardness of water, photography, geography, medicine)
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