Note for non Radio Amateur users of this software

These programs are aimed at Amateur Radio (AR) communications but they are all of general interest, especially for educational purposes.  The following items are all specific to AR operation although some have been encountered elsewhere, particularly the Maidenhead locator system.

SITES.DAT contains a lot of entries of the form G4JNT QTH.  These are the home locations of Radio Amateurs whose callsign is the G.. part; QTH is a 'telegraphese' abbreviation meaning location.  Just delete these when customising the database for your own use.

The Locator  eg  IO90IV  or IO90IV58 is a locator system based on Lat / Long that allows any location in the World to be specified by an alphnumeric code. An alphanumeric rather than all number system is chosen as it creates less ambiguity or confusion when quoted over a radio channel.  Originally invented by Radio Amateurs the Locator system has been seen in several other areas where it is often referred to as the Maidenhead locator (its original name, so called as its inventor lived there).  Normally used in its 6 character form, a mean accuracy of around 4km is possible at European lattitudes; the 8 digit form increases the accuracy to around 400m.  The format is as follows (note that the term 'square' is used very loosely; the shape in spherical geometry is anything but!) :

The first two letters specify Lat and Long in units of 20 degrees longitude (starting at -180 degrees) and 10 degrees of lattitude starting at the South pole.  The letters are allocated A = 0, B = 1 etc. Thus the bulk of the UK is in IO 'square' between longitude 20 Deg West and 0 deg, and latitude 50 - 60 Deg N.
( I = 8 so Long = -180 + 8 * 20  = -20 deg
  O = 14 so Lat = -90 + 14 * 10  =  50 deg  )

The next two digits divide this 'square' into 10 x 10 giving 1 deg lat and 2 deg longitude increments.  Thus 90 means:

9 * 2 = 18 deg N
0 * 1 =  0 deg E

Which are added to the Lat and Long given by the first two digits  ie  Long = -2 Deg   Lat = 50 Deg

The next two characters divide this smaller 'square' into 24 x 24 giving 5' Long x 2.5' Lat subdivisions.  Thus IO90IV gives : Long =  1ø 15'W   Lat = 50ø 52.5'N.  Since the centre of the 'square' is taken as the reference (unlike NGR where the bottom left hand corner is chosen) 2.5' and 1.25' respectively need to be added to obtain the correct conversion.  Thus IO90IV gives Lat = 50ø 53.75'N , Long = 1ø 17.5'W.

The second pair of numbers, used where the accuracy requires it, divides the 'square' above into 10 parts, and again the centre of THIS 'square' is used.    eg IO90IV58 = 50ø 54.62' N   1ø 17.25' W

To finally add confusion, two more letters can be added to further subdivide into 24 x 24 divisions of 12.5" x 6.25" (Seconds of arc). Thus IO90IV58EI = The tree in my back garden!  So far 10 digit locators have only been seen on certain up-market Global Positioning System receivers as the accuracy of 18m is rarely needed or even obtainable.

QRA as used in LOCATION is an older obsolete locator system applicable only to Europe, but still used (like feet and inches) by a few diehards!

The following are also irrelevant to non radio users of the software:

   TROPPATH program.
   K value in terrain (use K = 1 for optical sighting).
   Reference to mast heights unless climbing ladders.
   References to the Microwave Handbook (Published by the Radio Society of Great Britain)