gc_* functions

[khallock]

Port the NCL gc_* family of functions, including: gc_aangle, gc_clkwise, gc_dangle, gc_inout, gc_latlon, gc_onarc, gc_pnt2gc, gc_qarea, gc_tarea. The gc_* functions perform great circle calculations, such as whether a given point is located on a specified great circle arc (gc_onarc) or if a point is located within a polygon bounded by a set of great circle arcs (gc_inout).

[khallock]

I'm not sure where these functions rank in priority, but we received a bug report for the implementation of gc_inout provided by PyNGL. We may want to consider adding gc_inout (and other gc_ functions) here rather than fixing a version of it that we could instead deprecate from PyNGL.

[cyschneck]

• gc_aangle: Finds the acute angle between two great circles on the globe.
• gc_clkwise: Tests clockwise/counterclockwise ordering of points on spherical polygon.
• gc_dangle: Finds the directed angle between two great circles having a specified intersection point.
• gc_inout: Determines if a list of lat/lon specified points are inside or outside of spherical lat/lon polygon(s).
• gc_latlon: Finds the great circle distance (true surface distance) between two points on the globe and interpolates points along the great circle.
• gc_onarc: Determines if a point on the globe lies on a specified great circle arc.
• gc_pnt2gc: Finds the angular distance from a point to a great circle.
• gc_qarea: Finds the area of a quadrilateral patch on the unit sphere.
• gc_tarea: Finds the area of a triangular patch on the unit sphere.

[cyschneck]

Closed by NCAR/geocat-applications#65 (additional information via Project Pythia)