Spherical geometry other geometric concepts are defined as in plane geometry, but with straight lines replaced by great circles. Thus, in spherical geometry, angles are defined between great circles, resulting in a spherical trigonometry that differs from ordinary trigonometry in many respects; for example, the sum of the interior angles of a triangle exceeds 180 degrees. Spherical geometry is "not" elliptic geometry, but is rather a "subset" of elliptic geometry. For example, it shares with that geometry the property that a line has no parallels through a given point. Contrast this with Euclidean geometry, in which a line has one parallel through
OMB Circular A-16 to the policy described in the circular: Every agency that uses NSDI information must adhere to a set of responsibilities as outlined by the circular. OMB Circular A-16 OMB Circular A-16, revised August 19, 2002, is a Government circular that was created by the United States Office of Management and Budget (OMB) to provide guidance for federal agencies that create, maintain or use spatial data directly or indirectly through the establishment of the National Spatial Data Infrastructure (NSDI) and the Federal Geographic Data Committee (FGDC). The circular establishes guidelines for the management of digital spatial data and the use of