Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FIRE FIGHTING SYSTEM MAINLY CONCEIVED TO
SAFEGUARD FORESTS
The invention presented regards an integrated system which is
particularly well suited for the safeguard of wooded areas against fires.
At present, the problem of fires in wooded areas has reached
worrying levels. The forests of Argentario and Sardinia are sad evidence of
this.
The scope of this invention is therefore a system which offers
automatic monitoring of fires and which automates a fire propagation
model. The ~ltili7~tion of infrared sensors and of all the devices which form
the system, are a noteworthy step ahead in the safeguard of wooded areas,
till present trusted to towers and look out personnel. But of course the most
frequent inconvenience has always been the late arrival of fire fighters due
to the fact that there has never been an instantaneous detection of fire and
alarm transmission.
In accordance with one aspect of the present invention, there is
provided a forest surveillance and monitoring system for detecting and
reporting forest fires in a forest having an ambient infrared background
temperature, said system comprising: a peripheral detection station
including: means for collecting current weather data; infrared sensor means
for detecting a given surveyed area, said infrared sensor means being
operative to measure radiation f low along scan lines from a small angular
region of said area and to output corresponding signals; rotating means for
supporting the infrared sensor means and imparting an azimuth scan to the
infrared sensor means; local processor means connected so as to receive the
signals from the infrared sensor means and data from the weather data
collecting means; and a peripheral station co~ "~"~ications subsystem
connected to the local processor means for transmitting data therefrom; and
2 2~ ~7 ~
a local control center which includes: a historical data bank cont~ining
information on vegetation distribution and recent weather conditions in the
surveyed area; a com-llullication subsystem which receives data from the
peripheral station collllllunication subsystem and emits commands for
controlling the local processor, the local processor being configured to
manage a data exchange with the local control center; peripheral memory
means for recording data; and central processor means for controlling the
peripheral detection station, controlling an exchange of commands and data,
illustrating a notified alarm on topography maps of the area, recording data
on the peripheral memory means, displaying system status and integrating
the notified alarm with data of the historical data bank, the local processor
means being operative to provide for extraction of a fire alarm and to cause
transmission of an alarm signal and the weather data to the local control
center via the peripheral station commlmication subsystem and the
communication subsystem, the central processor means of the local control
center being operative to integrate the alarm extracted by the peripheral
detection station with instantaneous weather data and with data from the
historical databank so as to develop a fire propagation model as a function
of said integration whereby the model is based upon the instantaneous
weather data, the vegetation distribution, and the recent weather conditions
which results in a propagation speed and direction of a detected fire.
The invention, therefore, consists of two sub assemblies, namely the
remote detector and the local control centre. More than one detector can be
connected to the local control centre, in quantities from 5 to 10. For
illustrative non limiting purposes the invention will now be described with
reference to the table of drawings attached.
Figure 1 shows the block diagram of the entire system, where the
arrows stand for the connections among the units of the system:
7 ~
2a
Peripheral detector (usually each system includes more than
one detector; this block is expanded in Figure 2;
2 Communications subsystem;
3 Central processor;
4 Observed fire evolution prediction model;
5 Historical data base;
6 TV monitor;
7 Video recorder
8 Memory unit (hard disk, tape unit);
9 Printer.
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Figure 2 is a schematic representation of the
peripheral detector, indicated as block A in Figure 1.
Here we can see:
Infrared sensor;
11 TV camera;
12 Rotating platform;
13 Local processor;
14 Weather sensor group;
Communications subsystem.
More in detail, the remote detector consists
of:
An infrared sensor 10 which has a spectral
sensitivity such as to provide an optimum detection of
hot sources (300-700 degrees C) against an ambient
temperature background (0-40 degrees C). As regards
operation and structure of such sensor, refer to the
invention filed in Italy on December 21, 1989 with
number 48685-A/89.
A group of weather sensors 14 which provide
data on temperature, relative humidity, pressure, wind
speed and direction, solar radiation and rain rate.
A TV camera 11 for possible visual monitoring
of the surveillance area. A motor driven platform 12
which confers an azimuth scan to the infrared sensor
and to the TV camera over 360 degrees. A processor 13
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which acquires data from the infrared sensor and
provides for extraction of possible alarms, acquires
weather sensor data, manages data exchange with the
local control centre, from which it receives all
commands. The infrared sensor data processing is based
upon the following procedure: The infrared sensor
measures the radiation flow coming from a small angular
region, such as 1 x 1 degree; the vertical coverage of
the sensor is 15 to 20 degrees and is obtained by means
of a linear array of sensitive elements. All data
coming from a detector is taken into account: in our
case taken as an example, there are 360 datum points,
one per azimuth degree covered. The number of data may
be less if the area to be monitored is only part of a
whole round angle.
The processor calculates the value of the
derivative of the signal. This provides for the
elimination of the signal long term changing effects,
on an angle scale of 10 degrees for instance.
Such variations are typically due to the
variation of the angle between the line of sight of the
sensor and the position of the sun.
On the contrary, point variations are left
unchanged, when less or equal to 1 degree, as these are
typical signals of fires developing. The processor
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then extracts the mean square value of the fluctuations
of the signal subject to derivation for each group of
data corresponding to a given vertical position which
we shall call line.
Such value is proportional to the
fluctuations of the background on the line itself and,
multiplied by a suitable constant value, it is taken as
a threshold for the detection of possible signals.
Based upon the threshold determined above,
the processor identifies any signal present above such
threshold on a line basis. The azimuth angle of the
signal is compared with that of signals detected in the
previous scans. This is necessary to confer a better
reliability to the alarm through a number of
consecutive confirmed appearances.
In operation, an alarm is taken as true and
therefore transmitted to the local control centre only
if it has received a number of confirmations greater
than or equal to two in four successive scans.
It is to be noted that this procedure may be
completed by the peripheral detection unit in about
three minutes, therefore reducing the present detection
times of a fire in wooded areas quite considerably.
A communications system 15, such as a radio
link remotely controlled by the processor, provides for
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digital transmission of alarms detected by the IR
sensor, of weather data and of the TV image to the
local control centre.
At the local control centre, the transmitted
data is sent to units which perform their processing,
registration and integration with data available in
cartographic, thematic and historical archives. The
local control centre consists of the following:
A TV monitor 6 and a video recorder 7 for the
viewing and possible recording of the TV images coming
from the remote detection centres.
One or more processors with the following
functions:
A: Control of the peripheral stations, exchange of
commands and data.
B: Visualization of alarms, notified by the
peripheral detection stations, on topographic maps of
the area by means of three dimensional projection;
calculation of possible intersections between alarms
coming from different peripheral stations so as to
assure an even more accurate location.
C: Integration of alarms with instantaneous weather
data, with data banks containing information on the
distribution of vegetation, on recent weather
conditions and on human presence in the area.
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D: Following integration of data and as a function of
it, a fire propagation model is developed; such model
is described later on in detail and it is one of the
most innovative points of this invention.
E: Recording of data on hard disc or on peripheric
units 8 such as tape recorders or optical discs.
F: System status display including possible alarm
messages on printer 9.
We shall now describe briefly the procedure
adopted for the forecast of the evolution of the
observed fire.
The function provided by the program may be
performed during operation of the fire fighting system
(called in the following on line functions) or
separately (off line). The main functions performed by
the program are the following:
Digitizlng of topographic and thematic maps.
The data which is available from this digitizing are
the substrate absolutely necessary for the
visualization of alarms on the monitor display of the
processor and for the development of the forecast
algorithms of the fire development.
Peripheral management: This function,
preferably used off line, transports onto paper the
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graphics displayed on the monitori this is the
documentation required by the fire fighting squads.
Intervisibility management which is performed
between any point of the map and one of the peripheral
detection stations. This function is used mostly
during setting up of the system and it guides in the
selection of the best sighting of the peripheral
detectors.
Forecast of the fire development. The model
is based upon the speed and direction of the wind, on
ground slope and type of fuel, resulting in a
propagation speed of the fire as a function of absolute
azimuth against north. The algorithm utilizes the
following parameters:
~ Vfo = Intrinsic average speed of propagation of the
fire.
~ Vfc = Variation of the fire propagation speed
depending upon the type and humidity of the burning
vegetation. Data on the distribution of vegetation
is each time read from the data bank.
The effect of wind is quantified by the
following parameters which have an effect on the
propagation speed:
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~ Ci = increment constant due to the greater
oxygenation due to wind. It is independent of angle
with wind direction, but depends on its intensity.
~ Ct = transport constant of the fire front edge,
which depends upon the angle between the propagation
line and wind direction.
The program provides a graphic output
overlayed on the digitized topographic map showing the
successive positions of the fire front edge at pre-
established time intervals.
Now we shall proceed with the detaileddescription of system operation, with illustrative non-
limiting purposes, making reference to the two figures
mentioned above.
At the peripheral detection site (Figure 2),
the data which is detected by the infrared sensor l0
are acquired and processed by local processor 13. One
of the tasks of the processor is also the management of
rotating platform 12 onto which the IR sensor and the
TV camera ll are fitted. Following interrogation of
weather station 14, the processor transmits the
position of any possible fire together with weather
data by means of the communications system 15. The TV
camera transmits images directly to the local control
centre by means of the communication system.
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The data coming from the peripheric detection
station 1 is sorted by the communications subsystem 2.
The TV video is visualized on monitor 6 and can also be
recorded 7. The infrared sensor data regarding the
S position of any alarm is fed to processor 3 which
places them on the topographic maps. The modelling
program 4 develops a forecast of the fire evolution in
the hours following detections, relying upon historic,
weather, vegetation and other data contained in data
bank 5. The weather data acquired in the last scan are
inserted in the data bank.
All alarms are processed on the system
monitor, on printer 9 and possibly recorded on mass
memory 8.
