A manual for
       QKPFL,  "Quick Profile"

   This is a main program designed to illustrate one way to use the ITM
in the point-to-point mode.  Written long ago, it was meant to have punched
cards for input.  That is probably still the best way to imagine the
process, although we would now suppose the "punched cards" are each
represented by a single 80-column line in some file.  The program reads
such lines to define parameters and prints out tables showing estimated
quantiles of basic transmission loss versus reliability for a set of
confidence levels.  In addition to the system and environmental parameters,
the user must specify a terrain profile in the form of a sequence of surface
elevations taken at equally spaced points along the great circle joining the
two terminals.  The mode of variability is restricted to the fixed-link
communications service, but the user may choose the specific quantiles, both
of reliability and of confidence, for which computations will be made.

  *Input*
   Input is through a sequence of cards of eight different "types."  Each
type introduces a particular set of parameters or directs the program to
perform a particular operation.  The cards may appear in any number and in
almost any order and as many output pages for as many different systems as
desired may be produced.  The concept is that the information on any one
card will change values for the indicated parameters while leaving all other
values as they were previously defined.  When all desired changes have been
made, the user request an execution run, whereupon computations are made
and a page of output produced.  At the very beginning all parameters except
the terrain profile are assigned default values.  These are therefore the
values used unless the user explicitly changes them.  Furthermore, most
of the parameters must, by their nature, have strictly positive values; if
they are given zero or negative values on the input cards, the program will
simply ignore those values and therefore retain those previously given.  In
particular, since Fortran interprets a blank field as a zero value, such a
blank field may be used to indicate that the corresponding parameter is not
to be changed.
   The cards are read in 10-column fields, the first of which is a sequence
of digits and the remaining seven floating point numbers read with an F10.0
format.  Column 1 is always an "execute" indicator: if it is any non-zero
digit, then as soon as the card is processed, the program makes its compu-
tations using parameter values as are then defined.  The digit in column 2
indicates the card type and defines how the remaining digits in the first
ten columns and how the floating point numbers in the remaining fields are
to be interpreted.  In outline, the eight types can be described as follows:

               Col
               12        11, ...
               -------------------------------------------------------
Stop           X0            (or a blank card)
Title          X1            (with a 60-column title on the next card)
Profile        X2        d, xi, zsc
     (followed by a set of "profile cards".  These have 5-column
      fields in the format
               ENN  p0,  p1, ...)
Reliability    X3        qR1, qR2, ...
Confidence     X4        qC1, qC2, ...
Parameters     X7PC      fMHz, hg1, hg2, N0, Ns, eps, sig
Execute        X8
Reset          X9

   In this table we have begun the representation of a card with the execute
digit X in column 1 and the card type digit in column 2.  Following this
there may be single upper case letters indicating particular parameters with
single digit values and then there comes a sequence of variables.  These
latter are to be replaced by floating point values in successive 10-column
fields beginning at column 11.  The card types and definitions of the
variables are described in detail below.

  *Card Type 0: Stop.  When this card is read the program has finished the
job run.  If the execute digit is set, a page of output is produced first.
This card, which can be entirely blank, should be the last card of the input
file.  On many computers, however, it is unnecessary.  This is true if, upon
reading an end-of-file, the computer either leaves the input variables
unchanged or zeroes them out.

  *Card Type 1: Title.  If desired, the user may supply a short title which
will appear at the top of thge output pages.  This title will consist of the
first 60 columns on the card that immediately follow a card of type 1.  The
default title reads "Link predictions from the Longley-Rice model, version
1.2.2."

  *Card Type 2: Profile.  This card heads a subset of cards defining the
terrain profile.  The profile is given as a sequence of elevations
p0, p1, ..., pnp, taken at equal intervals xi from the point under the
first terminal to that under the second.  The total distance d between the
two terminals is then the product of np and xi.  On the header card one
must specify one or both of d and xi measured in kilometers.  The program
itself will count the number of profile intervals to arrive at the value
of np.  If both xi and d are given, the d takes precedence, but if it is
not at least approximately equal to np times xi, the program sets an error
flag and will not allow analysis of this profile.  The elevations them-
selves may be in any desired units if the scale factor zsc defines that
unit in meters.  (Since maps normally provide elevation contours in feet,
the foot will usually be the most convenient unit.  In that case, one should
set zsc equal to 0.3048.)  If zsc is not positive, or if the field is left
blank, the program assumes that the elevations are in meters and that zsc
equals 1.
   The digit T is a profile title indicator.  If it is not zero or blank,
then the card immediately following the header card contains a character
string describing the path.  The first 60 columns will be used as a subtitle
on each page of output.
   Following the header card or the profile title card, if present, there 
should be a set of elevation cards.  There may be any number of them, but
they must be in the proper order.  Each elevation card is separated into 
5-column fields the first of which is a sequence of digits and the remaining
fifteen floating point numbers read with an F5.0 format.  Column 1 is the
"exit" digit E.  If it is any non-zero digit, then as soon as the card is
processed the program stops reading elevation cards and either goes into the
computation phase (if the execute digit on the header card was non-zero) or
returns to reading further input cards.  The digits NN in columns 2 and 3
form a right justified one or two digit field count having values between
1 and 15.  The program will read the first NN fields on the card, attach the
values to the end of the terrain profile, and proceed to the next card.  If
NN is zero, the program will assume the elevation cards have terminated and
so go on to the next step.  Thus, inserting a blank card following the set
of elevation cards is an alternative way of ending that set.  (Note,
however, that if one uses both an exit digit on the last card and a blank
card following, then the blank card is not part of the profile set but is a
stop card which will halt the job run itself.)
   There are no default values for any of the variables involved.  Thus,
each time a profile set is provided, all values involved must be redefined.

  *Card Type 3: Reliability.  This card defines a sequence of reliability
values which will be used as the independent variable for which quantiles
of basic transmission loss will be computed.  Since we are speaking here
of a fixed-link communications service, reliability refers to the time
availability of hourly medians.  There may be from one to seven of these
values, all measured as percentages.  Each of the listed values will be
used in the order given to head a row in the output table.  Each use of
the card redefines the entire list of reliability values.  If none are
specified, the program defaults to a single value equal to 50 percent.
The original default condition uses three levels equal to 50, 90, and
10 percent, in that order.

  *Card Type 4: Confidence.  This card defines a sequence of confidence
levels which will be used as the second independent variable (the first
being reliability) for which quantiles of basic transmission loss will be
computed.  There may be from one to seven of these levels, all measured as
percentages.  Each of the listed levels will be used in the order given to
head a column in the output table.  Each use of the card redefines the
entire list of confidence levels.  If none are specified, the program
defaults to a single value equal to 50 percent.  The original default
condition uses three levels equal to 50, 90, and 10 percent, in that order.

  *Card Type 7: Parameters.  This card is used to specify the system para-
meters and parameters relating to the atmosphere and the ground.  The digit
P defines the polarization: 0 for horizontal and 1 for vertical polariza-
tion.  Since it can have the value 0, it must always be explicitly defined.
The digit C defines the radio climate according to the coded values:
             C = 1, equatorial
                 2, continental subtropical
                 3, maritime subtropical
                 4, desert
                 5, continental temperate
                 6, maritime temperate, overland
                 7, maritime temperate, oversea
If the digit is 0 or blank it is ignored, and the climate code used will be
the one previously defined.  The frequency fMHz is measured in megahertz
and is the value of the carrier frequency.  The heights hg1, hg2, measured
in meters, are the heights above ground of the antennas at the two corre-
sponding terminals.  If there is a question, it is the so-called center of
radiation of the antenna that should be used.  The parameter N0, measured in
N-units, is the surface refractivity of the atmosphere as reduced to sea
level.  The actual surface refractivity Ns will be computed from both N0 and
the average elevation as determined from the terrain profile.  If one wants
to introduce directly the value of Ns, this can be done in the next field.
If both fields have positive values, the value of N0 takes precedence.  The
dielectric constant eps of the ground and the conductivity sig measured in
siemens per meter are in the last two fields.  These are treated as a pair;
if the value of eps is positive, then the value of sig must also be sup-
plied; if the value of eps is not positive, both fields will be ignored.
The default values: vertical polarization (P=1), a continental temperate
climate (C=5), a frequency of 100 MHz, antenna heights of 3 m at both ter-
minals, N0=310 N-units, and an average ground with eps=15, sig=0.005 S/m.

  *Card Type 8: Execute.  When this card is read, the program immediately
makes its computations using the data that have been previously defined.
This is an alternative to setting the execute digit on the preceeding card.

  *Card Type 9: Reset.  When this card is read, the program will reset all
parameters to their default values and clear the terrain profile.  Any
following input cards may proceed on the assumption that they are effect-
ively the first cards in the job run.

  *Further Remarks*
   While the program was originally written in Fortran 66 and still retains
much of its older appearance, it now has some features of Fortran 77.  In
particular the "titles" mentioned above are now stored as character strings.