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Impervious surface percentage in various cities. The percentage imperviousness, commonly referred to as PIMP in calculations, is an important factor when considering drainage of water. It is calculated by measuring the percentage of a catchment area which is made up of impervious surfaces such as roads, roofs and other paved surfaces.
The basic quantities describing a sphere (meaning a 2-sphere, a 2-dimensional surface inside 3-dimensional space) will be denoted by the following variables is the radius, = is the circumference (the length of any one of its great circles), is the surface area,
A sphere of radius r has surface area 4πr 2.. The surface area (symbol A) of a solid object is a measure of the total area that the surface of the object occupies. [1] The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of arc length of one-dimensional curves, or of the surface area for polyhedra (i.e., objects with ...
The numerator is twice the area of the triangle with its vertices at the three points, (x 0,y 0), P 1 and P 2. See: Area of a triangle § Using coordinates. The expression is equivalent to =, which can be obtained by rearranging the standard formula for the area of a triangle: =, where b is the length of a side, and h is the perpendicular ...
A diagram illustrating great-circle distance (drawn in red) between two points on a sphere, P and Q. Two antipodal points, u and v are also shown.. The great-circle distance, orthodromic distance, or spherical distance is the distance between two points on a sphere, measured along the great-circle arc between them.
The extension of the problem to higher dimensions (that is, for -dimensional surfaces in -dimensional space) turns out to be much more difficult to study.Moreover, while the solutions to the original problem are always regular, it turns out that the solutions to the extended problem may have singularities if .
These formulas are identical in the sense that the formula for S oblate can be used to calculate the surface area of a prolate spheroid and vice versa. However, e then becomes imaginary and can no longer directly be identified with the eccentricity. Both of these results may be cast into many other forms using standard mathematical identities ...
Theoretically, Hooghoudt's equation can also be used for sloping land. [8] The theory on drainage of sloping land is corroborated by the results of sand tank experiments. [9] In addition, the entrance resistance encountered by the water upon entering the drains can be accounted for. Definitions of drainage of sloping land and entrance resistance