Re: Got one - distance calculator


From: Ronald C. McConnell (
Date: Wed Aug 22 2001 - 10:02:17 CDT

Hi, Phil,

I'm catching up on qrp-l reading.

that you found is the best web great
circle calculator of which I am aware.
There are other good ones like Ed Williams's

For the best introduction to great circle
navigation with worked out examples, see Ed's

If you want to "roll your own" with logging on,
my freeware great circle, lat&long/grid, MUF,
miles/Watt, etc.,
DOS command line program GCGC

may do what you want. It works in a DOS window,
and on HP 95 and Poquet PC DOS palmtops.
It has the US NGS forward and inverse
ellipsoidal earth model routines built in.
My main addition is a more usable interface.
(The filename is "9900," but is actually
the 2001/01 0r "0101" version.)

Unzip it into a new directory.
Skim file "read1st.txt" and "d2gread.txt."

Then a DOS command (in a DOS window) in a format like

  g lat1 long1 lat2 long2

or with real #s (degrees and minutes here for example)

  g 40 46.9 n 74 41.4 w 53.5 n 0 e

will calculate between my house and (near) London.
The lat/long/grid input format is pretty forgiving.

   40 46 54 n 74 41 24 w
   w 74.6900 n 40.7817
   n 40.7817 w 74 41 24
      etc. all work

If you store your lat/long as the first
(or only) line of ASCII text file "home.dat"
using Notepad or other text editor, then

  g + Cyprus p 3.2

will work between your house and Levkosia
and calculate miles/Watt for 3.2 Watts.

For forward calculations a DOS input line like

   g b 127.3 d 675.4

will calculate the lat/long from your coordinates
in home.dat for a point at a true bearing
of 127.3 degrees and 675.4 miles.

   g 675.4 k 127.3 d

also works. (Use "k" instead of "d" for km)

GCGC also calculates magnetic bearings using
the World Magnetic Model with 2000-2005 parameters.

I have plans for a Linux version of GCGC.
The source compiles. I just need to translate
the "g.bat" command into bash syntax
when I can get access to a Linux machine again.

Have fun.

Cheers, 73,

Ron McConnell

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