~TOP
>Spheric 1.20 ¸1994 by J.A.Wrotniak

  To choose a topic from the list below,
type its  first letter or two  and press
Enter.

>Topics

   * calculations    * keyboard
   * database        * menu
   * disk files      * prompts
   * Earth models    * settings
   * finding fixes   * registration
?
!CALCULATIONS
>CALCULATIONS
  These are performed from the CAL menu:
[FFd] - distance between two fixes
[Azi] - azimuth from a fix to another
[Mid] - midpoint between two fixes
[Aim] - fix at an azimuth and distance
[FAd] - fix-to-arc distance
[Prj] - projection of a fix on an arc
[AAd] - arc-to-arc distance
[Int] - intersection of two arcs/circles
>Topics
   * aiming        * intersection   
   * azimuth       * midpoint
   * distance      * projection
?
#DISTANCE
>DISTANCE COMPUTATION
  Distance-computing operations from the
CAL menu include:
[FFd] - distance between two fixes
[FAd] - distances  from a fix to a great
        arc and to the arc's circle
[AAd] - distance between two great arcs
 Depending on the [Set|Uni] setting, the
results will be in kilometers (km), U.S.
miles (mi), nautical miles (nm), degrees
of arc (arcø) or minutes of arc (arc').
>Topics
  * AA distance      * FF distance
  * FA distance
?
$FF distance
>DISTANCE BETWEEN FIXES

  [Cal|FFd]  finds the  distance between
two fixes, specified by their names.

  Instead of the first name a "+" can be
entered.   Spheric  will  then  use  the
second fix from the previous FF Distance
calculation,  and add the results.  This
way the total length of an  arc sequence
can be computed.
.
$FA distance
>FIX TO ARC DISTANCE
 [Cal|FAd] prompts for a fix and a great
arc, then finds two distance values:
- the "passing distance"  - from the fix
  to the arc's great circle (i.e. to the
  projection of the fix on that circle)
- the "closest distance"  - from the fix
  to the closest point on the arc itself
  Both results are identical if the pro-
jection  falls within  the arc; in  this
case a "*" will follow the result.
  Otherwise a "-"  or  "+"  will follow,
denoting  that the closest  point is the
arc's start or end, respectively.
.
$AA distance
>DISTANCE BETWEEN GREAT ARCS

  [Cal|AAd]  prompts for  two great arcs
(specified by  names of their  start and
end fixes), then computes  the  distance
between them, i.e. the shortest distance
between  any point on one arc and any on
the other.

  If the  arcs  intersect  (within  both
lengths) or overlap,  the result will be
zero.
.
#AIMING
>AIMING BY RANGE AND BEARING

 [Cal|Aim] computes a new fix at a given
distance  and azimuth  from a  given fix
(selected  by name).  You will be  asked
for all these three items.

- You  will be also  asked for a new fix
  name (optional) which  will be used to
  add the result to the fix database.

- Azimuth is measured clockwise from the
  North.
.
#AZIMUTH
>AZIMUTH

 [Cal|Azi] computes the azimuth from one
fix (selected by name) to another.

- The result  will be  shown  in ø and '
  or in decimals (degrees), depending on
  the current [Set|Ang] setting.

- Spheric measures azimuth from the true
  North, from  -180ø to +180ø,  with "+"
  defined clockwise (East).
.
#MIDPOINT
>MIDPOINT

 [Cal|Mid] computes the midpoint between
two fixes (selected by names).

- A midpoint is defined  as the point on 
  the great arc  connecting  both fixes,
  at the same distance from either.

- You  will be  asked for a new fix name
  (optional) which will  be then used to
  add the midpoint to the fix database.
.
#PROJECTION
>PROJECTING A FIX ON A GREAT CIRCLE
  [Cal|Prj]  finds  the  projection of a
fix  on an arc's  great circle.  Thia is
the circle's point closest to the fix.
- The distance  between the original fix
  and  its  projection  can  be computed
  with [Cal|FAd] (see "Distance").
- A "*","-" or "+" mark after the result
  will show  whether the  projection be-
  longs to the arc, precedes  or follows
  it, respectively.
- You  will be  asked for a new fix name
  which, if given,  will be used  to add
  the projection to the fix database.
.
#INTERSECTION
>INTERSECTION OF TWO ARCS
 [Cal|Int] finds the intersection of two
great arcs (each defined by names of its
two ends, see "Prompts").
 The  intersection  may be not "proper",
i.e. it may  be outside of  either arc's
span.  This is shown  by two characters,
one for each arc, which denote:
   "-" - before the arc's start fix,
   "*" - within the arc's length,
   "+" - after the  arc's end fix.
  For improper  cases, out of two possi-
ble  solutions,  Spheric choses  the one
which is closer to the arcs involved.
.
!DATABASE
>DATABASE OPERATIONS 
  The following database  operations are
available from the DAT menu:
[Loa] - load fixes from file  (append or
        replace; .FIX extension assumed)
[Sav] - save  fixes  to  a  file  (local
        directory only, .FIX assumed)
[Mem] - memory status (max.no.of fixes)
[Nam] - sort fixes by name
[Cat] - sort fixes by category
[Prx] - sort fixes by proximity  to  the
        currently selected fix
[Clr] - clear fixes  and/or  history (as
        chosen from the CLR menu)
  See also under "Disk Files"
.
!FINDING
>FINDING FIXES

- To find a fix,  start typing its name.
  As soon as you stop typing (one second
  break),  Spheric  will search  for the
  first fix matching the pattern.

- To find a fix  by its  category,  type
  the category preceded with a comma.

- Pressing  the  Tab key  will  find the
  next fix matching the pattern.
.
!EARTH
>EARTH MODELS
  Two Earth models are provided:

(E) Elliptical Earth (GRS 1980) with
    - Polar Radius = 6356.7523 km
    - Equatorial Radius = 6378.1370 km
(S) Spherical Earth, averaged to
    - Mean Radius = 6367.4357 km

  In either  case  all  calculations are
done on a sphere, except that in (E) the
geographic  latitude is  first converted
into geocentric  (the  opposite  happens
when results are displayed).
.
!DISK FILES
>FILES WRITTEN AND READ BY SPHERIC
  When [Exit] is pressed,  Spheric saves
a file SPH.ENV with all current data and
settings, then asks for confirmation.
  To exit w/o saving, press Shft-F10.
  SPH.ENV  is read  by the  program when
you run it, so that you can resume where
you left before.
  [Dat|Sav]  saves all fixes  as a plain
text file in the current display format.
When prompted,  enter  file name without
path or extension (.FIX assumed)
  [Dat|Loa]  loads a .FIX file as above,
with an option to clear the database.
.
!KEYBOARD
>KEYBOARD COMMANDS
  With no prompt shown at the bottom:
- Esc: show selected fix (full accuracy)
- Enter: edit the selected fix
- Ins: insert new fix (before selected)
- Del: delete the selected fix
- Up, Down: scroll by one fix
- PgUp, PgDn: scroll by page
- Home, End: scroll to top, bottom
- Bsp: delete history entry
- Left, Right: scroll history
- Ctrl-Left,-Right: history top, bottom
- Space - go to Cal or Set Menu
- Tab - repeat last fix search
.
!MENU
>MENU COMMANDS (TOP)
  The top function key menu includes the
following operations:

[Set]  - switch to the Settings Menu
[Cal]  - switch to the Calculations Menu
[Dat]  - switch to the Data Menu
[Exit] - exit the program
  In all menus the F1 key is marked with
the menu name  (here: TOP);  pressing it
brings this help.
  For the explanation of the other menus
see under "Settings", "Calculations" and
"Database".
.
!PROMPTS
>PROMPTS
  Prompts  at the bottom  of the  screen
ask for one of the following:
- A simple Yes/No answer: Y or N.
- Fix  name(s)  (changed to  uppercase).
  Use Tab for name  completion;  up/down
  arrows to recall recent inputs.
- Latitude  and  longitude  in  decimals
  (degrees) or in ø and ' (ALT+d for ø).
  A "-" can be used instead of S or W.
- Distance (in units as indicated).
- Azimuth (in decimals or in ø and ').
  At any prompt  Escape clears  input or
cancels the whole operation.
.
!SETTINGS
>SETTINGS
  Some  program settings  are accessible
from the SET menu:

[Uni] - set distance units
[Acc] - toggle distance display accuracy
        in the history log
[Ang] - set angle display mode
[Cat] - enable/disable  category  use in
        the history log
[Snd] - toggle sound on/off
[+/-] - set default signs of N/S and E/W
[Ert] - set the Earth model
.
!REGISTRATION
>REGISTRATION AND SUPPORT
  Spheric is shareware:  if you keep and
use it, send a fee of $30 to the author:
   Dr. J. Andrzej Wrotniak
   2057 Happy Lane
   Crofton, MD 21114-1917
  You will receive an upgrade to the "R"
(registered)  version  on a  3.5"  disk,
with a number of  enhanced  features.

  Comments,  questions,  suggestions and
problem  reports are  welcome and can be
also sent by email:
  GEnie: J.WROTNIAK    CIS: 46511,2552
.
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