Contents of the WCD.DOC file
* W O R L D C I T Y *
* D I S T A N C E C O M P U T E R *
* WCD Version 3.0 *
* (C)opyright 1988 *
* All Rights Reserved *
* GeoGraphics Software *
* 126 Mountain View Road *
* Glastonbury, CT 06033 *
* WCD is user-supported software provided to *
* you at no charge on a trial basis. If you use this *
* software and find it of value please register your *
* copy for $15.00 and support the shareware concept. *
* Registered users will be provided with information *
* about program updates. Please make checks payable *
* to G. K. Marek at the above address. *
* You are encouraged to share this software with *
* others provided that it is distributed complete *
* with documentation and in unmodified form and *
* that no fee or other consideration is charged or *
* accepted. All commercial, business and government *
* users must register each copy in use. *
* We hope you enjoy using WCD. Your comments and *
* suggestions to improve this product are always welcome. *
WCD, The World City Distance Computer, is designed to provide distance
and travel time information between over 400 different world cities,
including most major US cities. The program is windowed and menu
driven, and basically self-explanatory.
This program is designed for IBM Personal Computers and close
compatibles. It will execute on the IBM-PC, PC-XT, PS/2 and PC-jr. DOS
Version 2.1 or later is required. Since the program relies extensively
on color, a color monitor is recommended. The program will run,
however, unmodified, on the Compaq. WCD requires about 64K of memory
and does not require BASIC to operate.
The program is started by issuing WCD at the DOS prompt. You will see
the program loading city information from its built-in database of 400
world cities. It will also load in city data from a separate datafile
that the user can alter. More about this in the DATAFILE section.
Menu instructions appear on the left and a window of city information
appears on the right. Each city is identified by a three letter code
which represents that city's airport code. Some cities have several
airports. If the desired city code is known it can simply be entered at
the keyboard. If the code is not known, the window on the right can be
used to relate the codes to the respective cities. Use the scroll keys
to search this window for the three letter code of the city desired,
including the Arrows, PageUp, PageDown, Home and End keys. Pressing
[Enter] will select the city highlighted in the window.
The number keys provide functions to assist in specifying your desired
city pairs including a database search function. See the NUMBER KEY
section for detailed description.
The World City Distance Computer system comes in four files:
WCD.EXE executable program module
WCD.DAT extra cities information
WCD.DOC documentation file (ASCII); (this file)
WCDREAD.ME a short program description with latest changes
These files are packaged in a self-extracting archive file called
WCDARC.EXE which creates each file when the archive file is run.
The first two files must reside on the current directory or path for the
program to be accessible.
None of these files is copy-protected and it is suggested that the
archive file be saved in a separate place with your other archive and
backup files. Just run it again for a fresh copy of all the files.
To share this software with others, please transmit the archive file
so that the original program and files will remain intact.
NUMBER KEY FUNCTIONS
1- SEARCH for a particular string of characters in city list
2- ERASE start selection of this particular city over
3- RESTART start total selection process over
4- COORDS enter latitude and longitude instead of city name
5- LASTCITY use last city chosen as this city input
9- QUIT end program and return to DOS
DISTANCE INFORMATION SCREEN
Once all of the inputs are provided, a pop-up screen appears in the
lower left which contains output information. It includes distances
(both great circle distance and equivalent still air distance, which are
explained below) in three sets of units, the estimated flying time, the
direct bearing angle from the first city to the second, and an enroute
high altitude winds estimate. Negative winds are headwinds and positive
values represent tailwinds.
The computation of flight time is quite complex. The time for the great
circle flight is determined from empirical information on flight speed
as a function of route distance for jet aircraft. This time is then
corrected for winds based upon a model of world high altitude winds
using the specific route flown. This flight time is accurate to about
10 minutes or 10% of the elapsed flight time, whichever is greater. It
does not account for extraordinary traffic delays, airways that do not
closely follow the great circle route or enroute stops.
The bearing is the direction of departure from the origin city along the
great circle path toward the destination city. It is measured from the
origin by basic compass direction. Thus, the bearing from LA to New
York is 65 degrees (or about east-northeast) and the bearing from LA to
San Francisco is 320 degress (or about north-northwest). On longer
distances, the initial bearing might seem deceiving. For example,
the initial bearing from Tokyo to Los Angeles is 55 degrees, or east
north-east even though LA is actually south of Tokyo (33 degrees north
latitude for LA, versus 35 degrees for Tokyo). So the shortest distance
from Tokyo to LA actually starts off headed north even though LA is
more southerly! Try it with a globe and string to check for yourself.
A WORD ABOUT DISTANCE AND TIME
The distances computed are based upon the "great circle distance (GCD)"
between the two cities, which can be thought of as the route described
by a string pulled taut between the two cities on a globe. This
represents the shortest distance between the two cities.
These great circle distances between cities are geometrically correct.
For airplane flight purposes, however, prevailing head or tail winds
make the apparent distance different and should be taken into account.
High altitude winds can be greater than 60 knots and are significant for
the flight time calculation. For example, the great circle distance
between Los Angeles and New York is 2467 statute miles. But an airplane
travelling between these cities faces a prevailing headwind of 25 knots
when headed westbound (i.e. from New York to LA) and a prevailing
tailwind of 22 knots in the other direction. Thus the eastbound flight
is shorter in time than the westbound because it is assisted by the wind
rather than hindered. The "equivalent still air distance (ESAD)"
accounts for this wind effect. Flying against the wind, the ESAD is
greater than the GCD since the headwind causes the plane to fly longer
to reach its destination. Thus the ESAD from NYC to LA is 2611 statute
miles and takes 5 hours and 33 minutes (against the wind) while the ESAD
from LA to NYC is 2351 statue miles and takes only 5 hours and 2 minutes
(with the wind's help). This ESAD is used to compute the flight time
that accounts for the effects of enroute winds. So, although the great circle
distance between two cities is the same in both directions, because
of prevailing winds, the equivalent still air distances and the flight
times are not.
IF THIS CONFUSES YOU A LITTLE, just remember that the ACTUAL DISTANCE
between a city pair is the great circle distance (GCD) and that the
FLIGHT TIME is computed to include the effects of the wind in the
The program allows the user to include additional city pairs in a file
called WCD.DAT. This file is provided with the programs and contains
many additional smaller cities that the user may wish to select to be
included in the program when it is run. If you are satisfied with the
cities in the program itself and do not require additional cities, you
may remove this file (WCD.DAT) from the current directory to speed the
loading of the program.
Memory space precludes fitting all of the additional cities within the
program itself. As supplied, only 10 additional cities are selected for
loading. You can edit this file to select other cities or remove those
selected by changing Field A as instructed below. The user can also
edit this file to add other cities of his choosing. The format of the
file, sampled from the middle of the datafile, is as follows:
COLUMN 1 2 3 4 5 6 7
A B C D E F
0, GOONDIWINDI, QLAND AUSTRALIA, GOO, -28.31, -150.19
1, GOTHENBURG, SWEDEN, GOT, 57.40, -12.17
0, GRANADA, SPAIN, GRX, 37.11, 3.47
0, GUADALAJARA, MEXICO, GDL, 20.31, 103.19
0, HOBART, TSMNIA AUSTRALIA,HBA, -42.50, -147.29
The data columns are not critical, although retaining the existing
columns will make spotting errors easier. The commas between fields ARE
critical since they actually delimit (or separate) the data fields.
Field A- 1-INCLUDE in program; 0-Do NOT include.
Field B- Description of City Name
Field C- Additional description such as State & Country
Field D- A Three-Digit City Code designator (Numbers can be used)
Field E- The City Latitude (North of Equator is positive)
Field F- The City Longitude (West of Greenwich is positive)
In the sample data above, Gothenburg would be added to the program
while the other cities would not. The latitudes and longitudes are
given in degrees and minutes in this format: DDD.MM. Be careful with
the proper sign to differential north from south and east from west.
Entire lines of data can be added to or deleted from this file. Thus
you can add new cities such as your hometown. Lines deleted from this
file will make the loading process a little faster, so if you are sure
you don't care about a given city in this file you can eliminate it.
Your comments and suggestions for improvements are welcomed.
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