GENERAL INFORMATION
The program's initial default startup values are for Washington, DC, USA
and Paris, France.
This program computes the geodetic distance between two locations on the
Earth geoid. The maximum theoretical error is on the order of ±50 meters,
but the computed distance is rounded to the nearest ±0.1 (kmminmi).

LATITUDE/LONGITUDE CONVENTIONS
The standard longitude convention is Neg/Pos = West/East.
Everyone essentially knows that when we refer to latitudes, positive means
north and negative means south of the equator. Longitudes are a different
matter and more than one longitude convention can be used.
Although the program was designed with the standard coordinates system in
mind, where negative longitudes are west and positive longitudes are to
the east of Greenwich, if you prefer the opposite convention where east
is negative, then you can use that convention instead. Due to the basic
symmetry of the geoid, either convention will work equally well, so it
doesn't really matter which one you use as long as you're consistent
and apply the same longitude convention to both locations.

GEOGRAPHIC COORDINATE FORMATS
Coordinates may be obtained from https://www.gpscoordinates.net
and copied/pasted directly to this program interface in the same
Lat,Lon format as "+46.789, 76.543" and separated by a comma.
The coordinates may be entered as decimal degrees or as degrees,
minutes and seconds, separated by spaces. In either case, the
coordinates are separated by a comma and are not restricted to
purely integer values.
EXAMPLES OF VALID COORDINATE VALUES
+123.456789 = D = 1 element = Degrees only
+12 34.56 = D M = 2 elements = Degrees and Minutes
00 00 12.345 = D M S = 3 elements = Degrees, Minutes and Seconds
For Paris, France, the coordinates could be entered as:
+48.8363889, +2.3372222
or as
+48 50 11.000, +02 20 14.000
or as
48 50 11, 2 20 14
NOTE:
Different sources may differ on the precise geographic coordinates of some
major world locations. Some places are too large to apply a single set of
fixed coordinates. But certain fixed points can serve as benchmarks.

UNITS AND BASIC DATA:
UNITS:
1 Statute mile 1.609344 km
1 Nautical mile 1.852 km
EARTH DATA:
Equatorial Radius 6378.137 km = 3963.191 mi = 3443.918 nmi
Polar Radius 6356.752 km = 3949.903 mi = 3432.372 nmi
Polar Flattening 1/298.257 = 0.003352813
