S1R IDL library utilities involving a Sphere
This document describes a number of routines in the
JHU/APL/S1R IDL Library
(called the S1R library below)
that deal with drawing or computing values related to a sphere.
These routine fall into several broad categories:
- Routines for drawing spheres and on spheres.
- Routines for computing values related to positions on a sphere.
- Routines specialized for the earth as a sphere.
The S1R library contains a set of utilities
designed to make it fairly easy to make figures involving
a sphere. This might be useful in documenting the transformation
between two spherical coordinate systems as an example.
The names of these routines all have the form sph*.pro.
The first one to try is sph_demo which gives the following result:
Routines are available to:
- Draw a parallel of latitude between given longitudes
at a given radius.
- Draw a meridian of longitude between given latitudes
at a given radius.
- Draw a radius between given limits at a given latitude
and longitude.
- Draw text on the sphere within a given spherical bounding
box and at a given angle.
- Place an image on the sphere.
- Plot lines or points on the sphere.
- Handle hidden lines in various ways.
- Set colors, linestyles, and thicknesses.
- Set the size, position, and orientation of the sphere.
The S1R library contains a set of routines for computing
values involving spheres. Some of the computations invloving
a sphere are:
- Distance between two points.
- Range and bearing from one point to another.
- Find a point with a given range and bearing from a reference point.
- Find the intersection point of two circles.
- A page on Spherical Triangles is
also available.
The S1R library contains a several routines
involving the earth that may be useful with
the other spherical utility routines. These give the
capability to:
- Draw coastlines on a sphere.
- Find the sun's position over the earth.