FAST GEO-CHRONOMETER (FGC)
Version 1.0 1/4/90








TABLE OF CONTENTS


1.0 Program Features and Requirements. . . . . . . . . . . . . 1

2.0 Program Usage. . . . . . . . . . . . . . . . . . . . . . . 2

3.0 Customizing the Names and Local Times shown on the World
Map . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

4.0 Program Information. . . . . . . . . . . . . . . . . . . . 6

5.0 FGC Program Distribution Policy. . . . . . . . . . . . . . 6



LIST OF FIGURES

FGC Command Keys . . . . . . . . . . . . . . . . . . . . . . . 3
Label Specification Line . . . . . . . . . . . . . . . . . . . 5



















(C) Copyright Robert A. Fullerton 1990 All rights reserved



FGC Thursday, January 4, 1990 Page 1




1.0 Program Features and Requirements

This program, the Fast Geo-Chronometer (FGC), displays the
pattern of the sun's illumination on the surface of the earth.
Although there are several other programs available which perform
a similar function, FGC provides a unique combination of features
designed to make it the best choice.

These features are:

An accurate, fast, and attractive display that fully
utilizes the capabilities of an EGA/VGA graphics adapter.

Good accuracy over a wide time span. Sunrise and sunset
times can be determined to an accuracy of two minutes
(average), from the year 1980 to the year 2000, at any spot
on the earth's surface.

High speed display updates without requiring the use of a
math co-processor. On an 8 mhz AT, the display update rate
is 3 times per second.

Total user control of the city and area names and associated
local times shown on the world map display. The user can
edit a simple text file to specify any desired name label,
defining the label marker's position, whether the marker
will be hidden, the text accompanying the label, how this
text will be positioned, and whether a local time will be
displayed with the label (a separate local time zone can be
specified for each label).

A stylized (but geometrically accurate) world map is
combined with an appropriate set of text fonts and the
versatile label specification capability. The result is a
clean, attractive display that presents a large amount of
useful information.

Both a real-time and a single-keystroke-controlled variable
speed mode are provided, allowing the changing sun illumina-
tion pattern to be displayed in an optimal manner.


Hardware requirements are an IBM PC compatible computer, an
EGA or VGA compatible display adapter (with 256KB of memory) and
a color display.




FGC Thursday, January 4, 1990 Page 2


2.0 Program Usage

If your clock is set to Mountain Standard Time, the program
can be run without any required set-up. Simply enter "FGC" on the
command line. The files LABELS.DAT and FGCMAP.SCR must be in the
same directory as the program file FGC.EXE.

However if you don't live by Mountain Standard time, you
will need to specify your own local zone. This is done by
entering the difference in hours between your local time and
Greenwich Mean Time, and the 2 or 3 letter symbol for your time
zone, on line 1 of the data file LABELS.DAT. This can be
accomplished using any editor capable of editing in an ASCII text
mode - for example, WordPerfect's DOS text mode. A sample line,
for Eastern Standard Time, would be:

5 EST (this text would be put on line 1 of LABELS.DAT)


Examples for all US time zones, both for Standard and
Daylight Saving Time, are given in the LABELS.DAT file.

If you don't enter this information correctly, the time will
still be properly displayed in the main title block, but the
sun's illumination pattern will be improperly offset and the
local times displayed for other world cities will be incorrect.

The program starts in the real time mode, with the display
representing the current time (as specified by your computer's
internal clock). The display can be toggled to a variable speed
fast-mode by pressing function key 10. When the fast-mode is in
effect, pressing the '+' key will speed up the display (to a
maximum rate of one week per display iteration), and the '-' key
will decrease the displayed time-change rate. Pressing function
key 10 again will toggle back to the real time mode.

The program is exited via the ESC key. Function key 1
brings up a help screen.

The stored astronomical data in the program covers the years
1980 to 2000. When in the high speed mode, the program will
automatically reset to the current time when the year 2000 is
reached, and will remain in this automatic loop cycling between
the current date and the year 2000 until interrupted by the
operator. In the real time mode, the program will exit if the
DOS date is greater than Dec. 31, 1999.

All program command keys are summarized in figure 1.





FGC Thursday, January 4, 1990 Page 3







.------------------------------------.
| * ESC exits program |
| |
| * F1 brings up Help-Screen |
| |
| * F10 toggles the Speed-Up mode |
| --------------------------------- |
| When Speed-Up mode is active - |
| + :speeds up the time display |
| |
| - :slows the time display |
| |
| F2 :pauses the display |
| (any key continues) |
|____________________________________|


FIGURE 1
FGC Command Keys





FGC Thursday, January 4, 1990 Page 4


3.0 Customizing the Names and Local Times shown on the World Map

If you like the program, you probably will want to customize
the labels displayed on the map. This is done by editing the
label definition lines in the LABELS.DAT data file. Sample
labels for many world cities are provided. These sample labels
can be changed to real labels by moving them left to begin in
column 1.

For each label you can specify:

The label position (latitude and longitude)

The label text, and the position of this text
relative to the (possibly hidden) label marker

Whether a local time will be displayed below the
label text, and the GMT offset for local time at the
label's position

Directions for specifying your own labels are given in
figure 2 and in the file LABELS.DAT.




FGC Thursday, January 4, 1990 Page 5







.-- *n The digit n ranges from 0 to 8. It specifies how
| the text is placed relative to the label marker
|
| {2 3 4} { '+' represents label marker,
| {1 + 5} <-- { digits show relative text position.
| {8 7 6} { (0 specifies a hidden marker, with
| { text displayed at position 5.)
|
| .-- label text (as will be shown on display)
| | ( '_' specifies an embedded space in text.)
| | (With a single '_', marker is shown, but no text.)
| |
| | .--N or S latitude degrees (pos'n of label marker)
| | |
| | | .-- latitude minutes (optional)
| | | |
| | | | .-- E or W longitude degrees
| | | | |
| | | | | .-- longitude minutes (optional)
| | | | | |
| | | | | | .-- Optional, time display with label.
| | | | | | | Tnn.nn: nn.nn is GT offset (hrs)
| | | | | | | (range +/- 0.0-23.9,
| | | | | | | + = west of Greenwich)
| | | | | | |
-- -------- --- -- --- -- ----
*5 New_York N40 43 W74 01 T5.0 <------ label definition
(must start in column 1)


FIGURE 2
Label Specification Line





FGC Thursday, January 4, 1990 Page 6


4.0 Program Information

The program was written in Turbo C 2.0 and a Beta version of
Turbo Assembler 2.0. 1800 lines of source code were required.
The world map was created using EGA Paint 2005.

The requirement for a math co-processor was eliminated by
pre-computing all required transcendental functions, and storing
the results in lookup tables. All required astronomical data
covering the years 1980 through 2000 is also stored in tabular
form, thus reducing real-time computations to a minimum.




5.0 FGC Program Distribution Policy

Copies of FGC used only for non-commercial personal purposes
are free. A license fee is required for use by corporations and
institutions. This program may not be modified without my
written permission, and all rights are reserved.

A version of FGC that automatically adjusts for Daylight

Saving Time, for both the local time zone and the world cities
shown on the display, is available for a fee of $25.00.

If you are interested in either the upgraded version or
commercial usage fees, please contact me by writing to:

Robert Fullerton
HS Systems
886 E. 4070 S. #21
Salt Lake City, UT 84107