Note: Descriptions are shown in the official language in which they were submitted.
;~'26~7S
Field of the Invention
The present invention relates to a simulator for
simulating the discharge of an airborne material such as an
aerosol or a gas into the atmosphere.
Background of the Invention
When a hazardous chemical substance is discharged into
the atmosphere it is often difficult to predict concentrations,
the time of arrival of the substance at a given site and the
distribution of the substance by a wind. Of interest to civilian
authorities are the prediction of the paths of the hazardous
chemical clouds and the anticipated concentrations, so that they
can evacuate those people in populated areas where concentrations
could be dangerous. The same information is similarly useful for
military purposes.
The problem is thus to develop a system to display
substance cloud growth and progression in time, overlaying a map.
In order to serve emergency rather than planning purposes, the
predictions must be done far more quickly than the real time
spread of a cloud of hazardous chemical
Sum cry of the Invention
According to the present invention, there is provided a
simulator for simulating the progression of an airborne material
such as an aerosol or gas discharged into the atmosphere,
comer lo lung:
- display means for displaying a map of a selected area
and the location of a discharge on the map;
data recording means for recording data describing the
,,
-~.22667~;
discharge and ambient meteorological conditions;
computing meals for computing from the recorded data the
dispersion of the airborne material as a function of time; and
means for causing the display means to display on the
map the computed dispersion of the airborne material at a selected
time after initial discharge of the material.
Preferably, the simulator system is also capable of
predicting and displaying the concentration distribution of the
substance, the degree of danger at every location on the map, and
the time of arrival of the substance at any given point It is
also desirable to be able to predict reliably on the basis of a
continuing discharge of the substance or a single burst.
Since map data may not be readily available to the
simulator, it is also preferred to have a mechanism available for
sketching or tracing map data into the simulator for display
This can be done using a "digitizing tablet" or a "light pen" on
a video display terminal D
Brief Description of the Drawings
In the accompanying drawings, which are illustrative of
an exemplary embodiment of the present invention:
Figure 1 is a pictorial representation of the hardware
used in the exemplary embodiment of the present invention;
Figure 2 is a graph of the normal distribution model
used in the exemplary embodiment of the invention;
Figure 3 is a pictorial representation of a cloud from a
ground burst;
Figure 4 is a pictorial representation of a cloud from a
continuous source;
,
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Figure 5 is a display header sheet;
Figure 6 is a simulator menu display;
Figure 7 is a text menu display;
Figures 8 to 11 illustrate the use of the simulator in
the "draw" mode;
Figure 12 illustrates the Sims k~tor display in the
"wind" mode;
Figure 13 through 17 illustrate exemplary displays
generated on the simulator in the "simulate mode.
Detailed Description
Turning to the drawings, the exemplary embodiment of the
simulator, referred to as a "chemical event environmental hazard"
or simply "HAZARD" (TM) simulator is a combination of a
microcomputer I with a monitor I a digitizing tablet 16, a
light pen 18, a printer 20, IBM (TM) utility and BASIC programs
and a "HAZARD" (TM) program that will be described in detail in
the following.
The microcomputer 12 is an IBM personal computer with
two disc drives, OK memory, an asynchronous communication adapter
(SKYE) and a color graphics adapter. The monitor I is an RUB
color monitor. The digitizing tablet 16 is a summagraphics "BIT
PAD ONE". The light pen 18 is an FT-156 light pen from FOG Data
Systems. The hardware system is completed with an EPSON, McCauley
or MX-80F/T dot matrix printer 20.
The software component of the simulator coats with this
hardware to provide:
i) Menu prompted selection of the data input systems
(Figure 6);
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ii) A map input system through the digitizing tablet and
pen such that the map is generated on the monitor as
the pen moves figure 10);
iii) A visual data input system for meteorological data
using windowing techniques and a light pen (Figure
12);
iv) The simulation of a hazardous chemical cloud from a
continuous source showing relative concentration
levels, using selectable time intervals for forward
simulation and the use of windowing for screen
display simulation conditions (Figures 15 and 17);
and
v) The simulation of a hazardous chemical cloud from a
single burst (Figure 16).
The exemplary embodiment of the simulator uses certain
IBM disc operating system (DOS) version 2.00 programs including
DOS systems programs IBMBl0.COM, IBMDOS.COM and COMMAND.COM as
well as GRAPHICS.COM and BASICA.COM. All of these IBM programs
are proprietary to international business machines (IBM) and can
be found on their IBM DOS 2.00 disk.
The exemplified embodiment of the simulator also
includes the following programs:
AUTOEXEC.BAT
STAR TEAT
IIAZARD.BAS
EIAZARD.TXT
I've HAZARD.BAS program is the overall operating program for the
simulator. It includes map and wind condition input subroutines
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as well as a subroutine for generating the required simulation. A
listing of this program is given as Appendix "A". The HAZARD.TXT
program is a subprogram that can be called up to help a user of
the simulator. It is, in effect, a bulletin user's manual. The
data (text) is not included in the program listing appended to
this application as it is not an operating part of this system,
but only fixed text that is displayed to an operator for
information purposes.
The HAZARD simulator includes the two batch files,
"AUTOEXEC.BAT" and START BAT A batch file is a reserved
International Business Machines (IBM) "PCDOS Operating System"
(DOS) file name for files that contain DOS commands or the names
of other batch files. When a batch file name is typed in, the
commands in the batch file are executed as if they were being
typed directly in from the keyboard. The AUTOEXEC.BAT and
STAT BAT batch files allow the HAZARD simulator to be executed
when the computer is turned on with no help from a human operator.
The HAZARD simulator can be started manually by typing "basic"
and the HAZARD file name from the keyboard.
The AUTOEXEC.BAT file for the HAZARD simulator contains
the following commands:
a:graphics.com
start
rem welcome to DOS 2.0
The first line "a:yraphicsOcom" loads a DOS program into
memory to allow the contents of a graphics display screen to be
printed on a graphics printer when using a color/graphics monitor
adapter.
The next line "start" is a batch file that is executed
after "graphics.com". This batch file contains the DOS command
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"basic" and the HAZARD file name.
Before dealing with the operation of this system, it
will be useful to consider the theoretical basis of the plume and
cloud spread models employed in this exemplary embodiment. The
basic mechanism affecting the mixing and growth of a cloud of gas
in the atmosphere is the turbulence of the atmosphere itself.
Although a Cassius substance delivered as a result of an explosive
burst will have internal turbulence that promotes cloud growth by
entraining air around it, the internal turbulence soon decays and
becomes much the same as that in the ambient atmosphere. The
nature of this turbulence is described in Lyons, JO. Turbulence,
McGraw-ilill, 1975. As a result of the mixing with the atmosphere,
the boundaries of the expending cloud have a lower concentration
of the discharge substance than that found at the center of the
cloud. This variation in the concentration generally follows a
Gaussian distribution. By considering the initial mass of
hazardous material, lateral variations in downstream
concentrations can be calculated for given atmospheric
turbulence.
"Plume" and "cloud" models can be used to evaluate the
distance over which a cloud (single burst discharge) or plume
(continuous discharge) may continue to be hazardous. The
distribution of both types and source is dealt with by the
simulator.
The probability density function for homogeneous
isotropic turbulent flow takes on a Gaussian (normal)
distribution Particles governed by gradient diffusion take on a
distribution of the following general form (with no time
dependence)
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C2 x2
f = C1 exp (I -2
where Of, C2 are constants. This is also the functional form
for diffusion of a point source in a uniform flow.
The Gaussian distribution may be used to model
concentration levels in the radial direction of a circular burst.
A cross-section of a typical burst is shown on the left hand side
of Figure 2. A plan view is shown in Figure 3. The concentration
distribution for the cross-section is
r2
C(r) = Coax exp ( 2 )'
where C(r) is the concentration at radius r,
Coax is the maximum concentration, and r is the radius.
The volume under the burst is therefore
r2
V -I or C(r) dry Jo or Coax exp ( - - ) dry = I Coma%
In drawing the circles which border different concentration
regions in the burst, the circle which designates the outside of
the burst (the area beyond which there is a negligible
concentration level) has a finite radius. This radius,
ram may be defined arbitrarily as the point where the
function C(r) is 0.1~ of the peak concentration at the center of
the burst. In normalized coordinates, Max = 3.717.
2~75
The importance of the rrnaX definition is seen when
it is needed to simulate diffusion in the burst. Diffusion ox the
burst is simulated by increasing Max with time. Mass is
conserved by keeping the volume of the burst constant with time.
Based on a new burst size, rmaxr the volume is
r 2 r 2
V or Coax exp (I I dry - I Cm (1 - exp (_
o
But V is known from the original peak concentration. Thus, the
new peak concentration, for larger Max values, will be
Max 2
WOW 1 - expel Max ))
The rate of increase of Max decreases with increased wind
speed.
Once the new peak concentration is determined, the radii
corresponding to the desired concentration levels can be found
through the relationship (in real coordinates)
r I
I., Max )
C(r) _ C exp - -3.717 '
- Max 2
675
The continuous source model uses segments ox a circle to
simulate the boundaries of a turbulent jet. The angle of spread
for either side of the jet centerline may be chosen to be in the
range of 12 to 25 degrees in order to be close to typical values
for a turbulent jet. The trend to smeller angles of spread with
higher wind speeds maybe incorporated, The angle of spread of the
it jet at the outside boundary and the angles of spread of the
intermediate boundaries of concentration ranges are assumed to be
invariant with time. The concentration variation from the
centerline to the jet boundary is illustrated on the right hand
side of Figure 2. A plan view of the dispersion is shown in
Figure 4. The distribution is, Gaussian, analogous to that used
for the burst The concentration varies with angle, a, from the
centerline as follows
I/ a 2
O - Coax exp -3-717
where is the half angle of spread of of the jet.
From this application of the deterministic model time
required for calculation of various levels of concentrations
within the plume can be calculated The shaded areas of the plume
shown in Figures 15 and 17 are based on the concentration as a
fraction of the centerline concentration. For the single burst
model shown in Figure 16, the concentrations are based on volume
mixing rates. More sophisticated models can be used and speed of
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Sue
calculation can be considerably increased by using a more
sophisticated compiler. What is isnportant is that the
microcomputer calculates and displays results in a way that is
meaningful to the operations personnel. Color bands for survival
time or level of hazard end cloud fronts representing the
anticipated arrival time of the threat as well as population
centers exposed to the threat are meaningful factors. These are
displayed immediately on the screen and no numbers need to be
processed by the observer to comprehend the magnitude of the
event.
In the following, certain notation conventions are used
to distinguish between the text of the specification and the
following:
- screen messages
- keys pressed by the user
- words to be typed in by the user
To operate the exemplary embodiment of the simulator,
Ices must be pressed to choose courses of action. key on the
keyboard is referred to by its keyboard symbol or name surrounded
by brackets. The following are examples:
Escape Sue ~Esc>
Number 1 I
Fly key fly>
The following keys are referred to by their names:
Space bar lacy space bar>
Shift key shift>
Enter key venter>
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ennui reference is made to a rnessaye printed on the
monitor, the message is printed in bolt text. For example:
Press Space biro
when more than a one key must be typed in to respond to
a prompt, the response will be in bold text surrounded by double
quotation marks. For example: "used".
U _ the Simulator
There are three basic steps to using the simulator:
l) generate a topographical map;
0 2) select wind speed and direction;
3) obtain a graphical simulation of a hazardous
chemical event.
The map is venerated by drawing selected geographical
and cartographical features, for example bodies of water and
contour lines using the dicJitizing tablet A grid with loo moire
increments can also be placed on the map. Population indicators
can be superimposed on the map using the digitizing tablet as a
pointing device.
The wind direction is set using the licJht pen on a wind
O compass. The wind speed is set using the light pen on a bar
graph.
In the graphical simulation, the time that will elapse
between each plot of the dispersion and the source type (discrete
puff or continuous jet) is chosen using the keyboard. The source
location is placed on the map using the light pen. when the
source position has been selected, the options available are
running the simulation forward or backward in time, restarting the
simulation, or exiting from the simulation.
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On starting the simulator, the header display of Figure
5 appears on the monitor screen with the prompt preys
space bar to kitten. Pressing the space bar briny up
the main menu.
Figure 6 shows the monitor image itch contains the main
menu on the upper right side of the monitor. Menus will always
appear in this region of the screen The selection of a menu
choice is made using the function keys <F1> to I , and the
~Esc~ key.
0 EXIT Command
In general, the EXIT command allows escape or exit from
the current command or menu to the next higher command or menu.
With the header display (Err 5), pressing ~Esc~ will cause
exit from the HAZARD simulator operation to the IBM disk operating
system. In the DRAW command, pressing ~Esc> return the simulator
to the main menu. when the light pen is used, an EXIT is made by
pressing the light pen on the screen beside EXIT in the menu (i.e.
the ~Esc> key will not work).
HOPE Command
'0 The HELP command provides a brief set of instructions on
how to use the HAZARD simulator.
Pressing <F1> activates the HELP command and displays a
screen of text explaining one feature of the simulator. The
screen title is printed on the upper left corner of the screen.
The bottom line of the screen (Figure 7) displays the prompt:
Press space bar> to continue - ~Esc> to EXIT
Pressing the space bar will display the next screen of
text and <Esc> will return the simulator to the main menu. The
YELP instructions serve as an internal user's manual
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~.2~667S
DRAW Command
The DRAW command allows the production of a map on the
monitor screen using a digitizing tablet.
Pressing OF will bring up the DRAW menu on tune right
and display the map on the left side of the screen (Figure 8).
The cursor symbol "+" indicates the symbol that is used to show
the current position ox the pen on the digitizing tablet. If a
command in the DRAW menu needs more input, a second menu is
displayed on the lower right side of the screen. The map is
automatically saved when ON exit from DRAW and will reappear ON
reentry to the DRAW command.
C AR Command
The CLEAR command allows erasure ox the entire map. The
erasure is irreversible and cannot be undone. The CLEAR command
returns directly to the DRAW menu.
The CLEAR command is activated by pressing I
GRID Command
-
The GRID command places a one thousand moire grid on the
map (Figure 9). The map is then one kilometer square with one
hundred moire divisions. The GRID command displays the prompt
RID in the second menu area while it is busy and returns
directly to the DRAW menu.
LINE Command
The LINE command allows the drawing of lines, such as
contour lines, on the map. These appear on the zap as dashed
lines.
Pressing <F3> activates the LINE command and opens a
I 75
second menu (Figure 10) prompting the use of Esc to EXIT from
the LINE command and return to the DRAW menu. The "I" cursor on
the map indicates the current position of the pen on the
digitizing tablet. Moving the pen across the tablet will move the
cursor across the map. The pen has a switch that is activated by
pressing lightly down on the pen. This switch is used to activate
line drawing. Drawing a map line involves the following steps:
1) Placing the pen or cursor where the line is to start.
2) Pressing) down on the pen and tracing the line on the
digitizing tablet.
3) Lifting the pen to stop drawing the line.
PEOPLE COMMAND
The PEOPLE command allows the placement of population
symbols on the map to indicate areas inhabited by people. The
population symbol appears on the map as a "happy face" (Figure
11~ .
Pressing ~F4> activates the PEOPLE command end opens a
second menu prompting the use of ~Esc> to EXIT from the PEOPLE
command and return to the DREW menu. Like the LINE command, the
"I" cursor indicates the current position of the pen on the
digitiæiny tablet. Placing a population symbol on the map
involves these steps:
1) Placing the pen or cursor on the map where the symbol is
to appear
2) Briefly pressing the pen down to place the symbol on the
map and lifting the pen
If the pen is held down to long, more than one symbol
will be drawn and the simulation graphics may be obscured.
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PRINT Command
The PRINT command makes a printed paper copy of the map
using the dot matrix printer Pressing showoff end protozoic>
together activates the PRINT commend.
Before using the PRINT command, mace sure the printer is
turned on, connected to the computer, and the paper is set to the
top of a page. I-E the printer is not ready to print, the computer
will remain inactive for approximately twenty seconds, after which
you can continue. After printing a copy of the screen, the
Lo simulator will return to the DRAY menu.
LOAD COMMAND
-
The LOAD command loads a map into the computer from a
file on floppy disk
Pressing ~F5> starts the LOAD command, which prompts you
to enter an eight character name of the file where the map is
stored:
Enter ILLUME -I ?
Exit from this command is by pressing venter> .
The following is an example of the typical steps that
I are used to load a map from a DOS file
1) Press <F5~ to activate the LOAD command.
2) Type in the 1 to 8 character name of the file containing
the map, frame for example, and press entry .
(vote: only maps saved using the SAVE command described
below may be loaded using this command.)
If the file is found, the message:
Loading fnameO~P
will appear as the map is loaded. If the file is not found, the
prompt:
, J.. I '
~t;675
fnam~.~AP not found, Press essay
is displayed. On pressing <Esc> the prompt:
Enter PHYLUM ->
will reappear.
SAVE Command
The SAVE command saves a map as a file on a floppy
disk.
Pressing EYE activates the SAVE command, which prompts
the entry of a one to eight character name under which the current
map image is to be stored. Exit from the SAVE command is by
pressing entry .
A map is saved using the following steps:
1) Pressing <F6~ to activate the SAVE command.
2) Typing in the 1 to 8 character name chosen for the map
file, frame for example, and pressing Enter
The massage:
Saving fnarne~MAP
appears while the file is being created.
WIND Command
I The WIND command allows the insertion of the wind speed
and direction using the light pen.
Pressing <F3> activates the WIND command and displays
the current wind speed and direction on the screen, as shown in
Figure 12. The left section of the screen contains a compass
which indicates wind direction and a bar graph which indicates
wind speed. The right side of the screen contains the WIND menu.
The menu choice is EXIT to end the wind data selection and return
to the main menu, The EXIT command is executed by pressing the
light pen in the white box beside Exit
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.. . . ..
Jo 2~6~75
The wind direction is chosen by pressing the light pen
in the ring around the compass The wind will blow towards the
point at which the pen is pressed. For example, by pressing the
light pen down in the ring just below the letter "N", a south
wind, bearing approximately 3303 miss, will be stored. The
accuracy of the FT-156 light pen on the IBM Color Monitor is
limited. Therefore, precise selection of some wind ankles is not
possible in this embodiment.
The wind speed is chosen by pressing down with the light
pen in the box above the desired wind speed. The length of the
colored bar in the box indicates the current wind speed. In this
embodiment the wind speed is selectable only in increments of
approximately 1.33 km/h because of the accuracy of the light pen.
SIMS Command
The SUE command runs the simulator
Pressing ~F4> activates the SIMS command, whereupon
the simulator uses the map and wind data created using the DRAW
and WIND commands to run a graphical representation of the
dispersion of a chemical agent. If the SIMS command is executed
before creating a map with the DRAW command, the message:
Map does not exist'
appears briefly on the bottom line of the screen. The main menu
remains and is active again after the message above is gone.
The first screen that appears in the SIMS command is
shown in Figure 13. The map is redrawn and the simulation
information is displayed on the right side of the screen. The
wind direction and speed and map range are given to aid in
selecting an appropriate time step and source location. Also
s
Shown is a legend of the color patterns which represent the three
ranges of concentrations: DANGER, WARNING, and SEE.
Before the simulation can proceed, the time step and the
source type and its location must be selected.
The time step is the increment in time which the
simulation will progress. us shown in Figure 13, the prompt that
first appears at the bottom of the screen is:
Time step is 1.0 Lange 7 ok? no
since the default time step is one minute. Pressing my> accepts
0 the time step. If on> is pressed, the following prompt is
produced:
Enter time step twin):
to which the operator responds using the number keys in the top
row of the keyboard and the ~.~ (period) key. The maximum
allowable time step is 1000~0 minutes. The desired time step, 1.2
for example, is keyed in and venter> is pressed. The prompt for
verification will appear again as:
Time step is I minor ox? (y/n)
Pressing > accepts this step, while pressing on> rejects it
'O There are two options available, should a mistake occur in keying
in the time step. The first is to backspace over the mistaken
Iceystrokes using the left arrow cursor movement key, found on the
right of the keyboard, and type over them with the correct values.
The second option is to press venter> , respond on> to the new
verification prompt, and retype the value.
There is a choice of two types of chemical sources in
this simulator The first is an aerosol generator type (A) which
is a continuous source of chemical agent. The second is a ground
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burst chemical simulator type (GBCS) which is a single discrete
puff of chemical agent Roy default source type is AGO After the
time step has been accepted, the prompt on the bottom line of the
screen will be:
Source type is Go ok? (yo-yo
Pressing < I> accepts this source type. Pressing on> will produce
the prompt:
Source type is GBCS, ok? no
Pressing my> will accept GBCS as the source type. Pressing on>
will switch back to source type AGO Switching between the two
types continues until my> is pressed.
Once the source type is selected, the following prompt
appears on the bottom line of the screen:
-> Set source with light pen <-
To set the source location press the light pen down on the map
where the source is to he placed.
After the source location has been set, the SIMS MENU
for control of the simulator appears in the upper right corner of
the screen as shown in Figure 14. Also, the bottom line of the
screen prompts with:
Enter menu choice with light pen
A SIMS MINI] command is activated by pressing the light pen in one
of the boxes beside this colnmarld name. The four light
pen-activated choices in the SIMS MENU are:
l) FORWARD - run the simulation forward one time step;
BACKWARD - run the simulation backward one time step;
3) RESTIMULATE - restart the simulation at the time step
prompt;
4) EXIT - exit simulation and return to the main menu.
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The Prolate command may also be chosen at any time to produce a
printed hard copy of the screen contents.
The FORWARD Command
.
The FORWARD command runs the simulation forward one time
step and displays the boundaries of the source-contaminated
regions. This command is activated by pressing the light pen in
the box beside FORWARD. For the GBCS source, all time steps up to
the current one are shown so that the user can trace the path of
the single puff. When the maximum of 9 (nine) time steps is
lo reached, the message:
Max no ox time frames!
will appear in the bottom line of the screen. At this point,
another command must be chosen
Figures 15 and 16 illustrate, for A and GBC~ sources
respectively, the result of placing the source in the upper left
courier of the map and choosing FORWARD twice. The boundaries are
shown for an elapsed time of I minutes, a wind speed of 23.3
km/h, and a wind direction of 5656 miss.
The BACKWARD Command
The BACKWARD command runs the simulation baclcward one
time step. This command is activated by pressing the light pen in
the box beside BACKWARD If the elapsed time is at 0.0 seconds,
the time will remain at zero for any further choice of the
BACKWARD command.
Figure 17 displays the A source boundaries one time
step backward from the results shown in figure 15.
The R~SIM~LTE Command
The RESTIMULATE command halts the current simulation and
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allows restarting of the simulation, beginning at the time step
prompt. This command is activated by pressing the light pen in
the box beside RESTIMULATE. Thus, using the same wind speed and
direction as before, changes can be made in the time step, the
source type, or the source location.
The EXIT Command
The EXIT command stops the simulation an returns to the
main menu as shown in Figure 5. This command is activated by
pressing the light pen in the box beside EXIT.
PRINT _ Monday
The PRINT command makes a printed paper copy of the map
using the dot matrix printer. This is activated by pressing
iffy protozoic> together. After printing a copy of the screen,
the simulator will return to the SIMS menu.
The chemical agent plume dispersion models used in this
exemplary simulator are not intended to produce precise results
which exactly match a practical situation. The models used to
display the plume and cloud boundaries are very simple in order to
speed up the display process. The quick display is important
since the purpose o-f the simulation is to enable rapid prediction
and reaction. The detailed calculations required for more
realistic plume models are possible with more powerful computer
hardware and software. Thus, in other embodiments where more
detailed predictions are required, models may be used that account
for ground contours, building concentrations and other
geographical features. The exemplary embodiment is also limited
to a 100 meter map grid. In other embodiments, the map scale will
be variable to provide more flexibility. It is also to be
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understood that various modifications in the hardware system are
also possible, for example using a portable rugged micro computer
end fewer manual input systems. Meteorological conditions,
including wind, humidity, precipitation etc. may be entered using
a direct input from appropriate instruments.
, .
