Spheric does spherical geometry calculations on the Earth's surface.

Enter two points (or a whole series of them) and have the distance (or the cumulative distance) computed and expressed in units of your liking: miles, nautical miles, or kilometers. Define a great arc (the shortest line between two points) and a point, then have the distance between them computed. Or find an intersection of two great arcs.

Of course, azimuth calculations are also included: find an azimuth from one point to another, or, less trivially, find a point at a given distance and azimuth (range and bearing) from a given one.

In particular, two functions are quite difficult to find in any other program:

• Geodesic distance and azimuth (geodesic line is the shortest path between two points on the Earth ellipsoid).
• "Elliptic great arc distance", measured along a line drawn on an ellipsoid so that its projection on a sphere is a great circle arc.

The program stores a number of points on Earth and then allows you to refer to them by names. It will also accept data from an ASCII file (or write to one).

Various display and input formats are supported: deg/min/sec, decimal degrees, deg/min/fraction. (And yes, conversion from geographic to geocentric latitude, strangely omitted in quite a few programs of this kind, has not been forgotten about.)

Spheric does not use the common trigonometric formulae to do its calculations; instead, it performs them on three-dimensional, Earth-centered vectors. This provides greater speed (which may be not so important), but also, first of all, unmatched internal accuracy better than 0.1 m (of course, within the Earth model used). Actually, it may be the most accurate program of its kind, regardless of price (and this includes U.S. government contracts).

Most of the casual users will never need this program's power (although, of course, they may easily use it). Serious ones, however, will find it indispensable.

And yes, of course, a registration is valid for the lifetime of the program, including any updates and upgrades.