Real-Time and all-weather
Quasi-Real-Time Montoring System of Remote Sensing information on the
flood dangerous state and losses
Cao shahu
The
Remote Sensing Center of The Ministry of
water Resources Beijing, China
Abstract
This paper introduces to the
remote sensing information system for real-time or all weather
quasi-real-time monitoring flood, which synthesizes the application of
remote sensing (technique), communication (technique), and geographic
information technique. It will be helpful for the headquarter of flood
control to see the flood area over thousands kilometer away from the
headquarter and understand the flood level and its change. Besides, the
system can investigate the losses of flood submergence quickly by using
flood control database. Thus the headquarter can make the precise judgment
and take emergent measure to reduce the losses in the life and property of
the people.
Real-Time Monitoring System of Remote Sensing
Information on the flood dangerous state and losses of the yellow river
basin
- The composition of the System
The system is composed of
the following two subsystems----real time transmission subsystem of
aerial images and level data of flood and flood-control Database of
flood detention and storage area in the Yellow River Basin.
Real
- time transmission subsystem of aerial images and level data of flood
consists of remote sensing plane, automatic measuring station of
water-level, transition station of aerial images and level data,
communication satellite and microwave relay station, receiving and
recording station and processing center.
Remote sensing plane is
used to trace the flood of the yellow River. On the plane, high
resolution TV cameras real-aperture (8mm) side-looking radar take the
images of flood level-receiver receives level data from automatic
measuring station of water-level, and transmitter sends the level data
and flood images to Transition Station. Moreover communication line is
equipped on the plane so that the position of plane and the state of
flood can be timely reported and the communication connation can be
continuously kept.
The automatic measuring station of
water-level, which consists of level sensor and level data transmitting
device, monitors the level and its change of the test section.
The transition station receives flood images and level data from
the plane, and then put them into microwave communication lines and
sends them to a communication satellite respectively. Receiving device
of flood images and level data, microwave communication equipment, TV
transformer and small satellite ground station are equipped in the
transition station.
The communication satellite and the
microwave relay station are used to transmit flood images and level data
real-timely and in long distance.
The processing center real
-timely receives, displays and records flood images and level data of
the yellow communication lines, and put them into computer image
processing system, which can process them and output the results. The
equipment of the center include: receiving device which receives flood
images of the Yellow River transmitted to Beijing by the microwave
communication lines, satellite ground station which receives flood
images and level data transmitted to Beijing by communication satellite
relay, and transformer, display device, video recorder, computer image
processing system and the like.
The receiving and recording
station has TV set and video recorder.
Flood-control database of
flood detention and storage area must be in advance established, so that
the losses can be quickly calculated by using real -time transmission
subsystem of flood images and level data when the Yellow River in
flooded. A great amount of information about natural and social
economics in flood-plain and detention and storage areas are digitized
and put into computer. Special management software has been studied. The
data of flood-control database include height, land -use state,
settlement and social economic data, because height data are essential
to determination of submergence scope and water depth and the data of
land-use state, settlement and social economic data, because height data
are essential to determination of submergence scope and water depth and
the data of land-use state, settlement and social economics are
necessary for calculation of losses. Height data are acquired by
sampling from topographic maps (1:10,000) according to the grid of 100mx
100m. In order to acquire the newest land-use state data, we specially
took aerial colour infrared images before the flood of this year,
complied land-use state map (1:50,000) based on visual interpretation of
them, and finally got land-use data by digitizing the land-use state
map. Settlement and social economic data, which are generally point
distributive, are collected by using topographic maps (1:5-0,000) and
social economic investigation information concerned (lack in the data of
factory-enterprises). The total flood-control data in this test are near
4,000,000. Moreover, we have studied the programs of data input,
storage, revision retrieval, statistics, form composition and graphic
display and output, etc.
- Introduction to the Test
We got great successes in this
test of the system on August 22, 1988. While the plane flys above the
Yellow River, sensor takes flood images and level receiver receives
flood level data from the automatic measuring station of water-level.
Transmitter on the plane sends the remote sensing images and level data
to Liutun transition, where they are divided in to two channels to be
transmitted in long distance. In one channel, images and level data are
transmitted to the satellite 5 of the International Communication
Organization, and sent to Yungang communication satellite main station
in Beijing by the satellite.
After signals are enhanced, the
Remote Sensing Center of the Ministry of Water Resources receives
displays and processes them. Because of the limitation of signal-channel
width of communication satellite used in this year, stationary images
and level data of flood are transmitted to Beijing. In the other
channel, flood images are transmitted to CCTV through the microwave
communication lines of the Broadcasting and Television Department of
Henan Province and the Post Ministry, and then are sent to the Remote
Sensing Center of the Ministry of Water Resources through the microwave
communication line from CCTV to the Ministry of Water Resources. When
the images of flood in the channel are transmitted to Zhengzhou, the
Television Station of images of flood in the channel are transmitted to
Zhenghou, the Television Station of Henan Province televises them by the
ninth frequency channel. Therefore, the Water conservancy Committee of
the Yellow River can real-timely receive and record the flood images.
The flood images transmitted to Beijing can be put into computer within
3 seconds.
The images, which have been processed, can be output
in hardcopy within 75 seconds. The submergence scope and losses can be
retrieved in flood-control database by using level data or one village
name on the flood boundary line, and submergence scope map and Chinese
and English loss tables can be quickly output, thereby the level data of
flood, submergence scope and losses can be quickly output, thereby the
level data of flood, submergence scope and loses can be quickly provided
to the flood-control command departments. The deference is 2.9 percent
between the losses retrieved in flood-control database by using
real-time flood image around Zhongwanzhuang and Outan one day of 1988
and ones investigated by the Water Conservancy Committee of Yellow River
in the field of the same day we are satisfied with the result.
All-weather and Quasi-Real-Time Remoter Sensing
System for flood monitoring and flood control data base of the
Jinjiang-Dongting lake region.
- All-weather and Quasi-Real-Time Remote Sensing System for Flood
Monitoring.
For the sake of flood monitoring possibly done at any
time under any conditions a quasi-real-time and all-weather remote
sensing system for flood monitoring was designed in 1989, upon the
experience of the remote sensing application tests on flood-control of
the Yellow river in 1988. This system is composed of airborne SAR,
optical imaging, image transformation, image transmission and image and
data processing.
It is known that an airborne SAR allows 24
hours monitoring a day, whether it is fine or not, covering wide area at
high flying speed. The films of data acquired can become films of image
through optical correlation. The images from the films of image are laid
together so that a mosaic showing a flooding river is obtained. With the
radar imagery, which clearly shows the water body and the content of
water in soil, it is easy to define the bound of a flood, therefore it
is a very helpful tool for a flood-control commanding unit to make out
the severe ness of the flood within a wide range. However, viewing that
the process of producing imagery is too long, it is certainly not a
real-time system for flood monitoring or a quasi-real-time system even.
To increase its effectiveness, an image separator is developed, which
can be mounted on front of the slit of the optical correlator. Not
affecting optical imaging, the device allows the use of CCD camera to do
the optical-electrical transformation of the separated imagery, and by a
signal devise the transformation image signals can be turned into full
TV signals for transmission and display.
Thus, it gains a lot of
time. Moreover, to identify the position of an object in the imagery
received and displayed, maps of study area are put into a microcomputer
by way of video camera, and display on screen. With the special software
developed, the monitoring range and the transmission channel are
overlaid on the
map. To indicate on the map the transmitted
image, a signal plane is designed, which can move synchronously on a
given image channel with the display on another monitor.
To test
the performance of the system, we monitored the second flood peak on the
night of August 11, every thing was carried out according to the planned
time table. Transmission started only one hour and 5 minutes after
landing, comparatively it is 13 hours ahead of that by conventional
means. The transmitted imagery moreover was made 4-fold larger than the
original, with topography, type and water conservancy profects etc
clearly identifiable. The same good result was also obtained in the
similar test carried out in the Jinjiang-Dongting Lake region.
- Flood-control Database of the Jinjiang-Dongting Lake
Region
In collection, vector digitization and raster digitization
techniques were used to derive DTM data from topographic maps (1:10,000)
of the test area, over 900 frames in all.
After the
vector-raster transformation densification of the collected data was
done with computer, topographic height data with 50mx50m interval were
obtained. Then, with the Landsat TM data recorded in tapes, the A/D data
of the SPOT imagery and with the special software, automatic recognition
and classification were carried out, in order to obtain the land use
data on the 9 types of area-featured objects in the test area (such as
irrigated land, arid land and forest). To secure the accuracy of the 7
line-featured objects (dam, road for example), vector technique was
taken to extract the relative features out of the map including water
conservancy maps and communication map; and after vector-raster
transformation with the computer and superposition of them with the
land-use data on the 9 types of area-featured objects, land-use state
data of the whole test area were obtained.
As for the
acquisition of the data on settlement and social economy, to ponym
dictionaries were first referred to define their names; after that,
1:50,000 topographic map were used to determine their positions. Then,
height data were adopted to determine the height of those points which
were then encode and put into the computer together with their social
economic data obtained from investigation.
For each settlement,
generally there were 15 data items, With the names, attributes, fixed
capital, annual output of industry and agriculture, and even the number
of the rooms at the settlement fed into the computer, data on the
settlement and social economy of the test area were obtained. In
general, in the establishment of the flood-control database of the
Jinjiang-Dongting Lake region, about over 90,000,000 data were processed
and stored, which have basically met the requirements for the loss
estimation. These, together with the developed software's for input,
revision, inquiry and output, have laid sound foundation for future
investigation of flood conditions in the area. Prospects of
flood-control Remote Sensing
The flood control remote sensing tests
carried out in 1987, 1988 and 1989 have not only turned out great results
but also displayed the potential and good prospects in suing remote
sensing and GIS techniques against flood. We assume that a future remote
sensing information system of practical value for real-time monitoring of
flood should include the following two parts:
- A remote sensing plane with multi-functions. It has powerful
non-stop flying capability, good enough to fly from Beijing to any part
of the seven longest rivers in China, carry out the mission and fly
back, and has all-weather flying capability. Aboard, all-weather SAR or
an advanced photographic camera or a high resolution video camera can be
changeably mounted, depending on the weather and work.
- In addition, there are such equipments such as: a hydrographic data
acquisition system, a transmitting equipment that can transmit the
collected data and the flood imagery to a communication satellite and a
dual communication system that assures communication between the plane
and the base.
In the processing center there should be a set of
computer image processing system, capable of receiving real-timely and
processing at high speed all the data concerned with a flood. The system
should have large external memories and more complete peripherals
Besides, there also should be a set of receiving equipment in the center
that receives the imagery from the Polar meteorological Satellite (PMS).
About the operation with such a practical flood-control
system, there are following presumptions:
- Constant monitoring of the water situation about the seven longest
rivers during rainy season is to be done by taking advantage of the PMS
imagery, so as to know where is flooded timely.
- A multi-function remote sensing plane will be dispatched to the
flooded area discovered by the PMS to acquire imagery and level data and
to transmit them to coruscation satellite, which relays them promptly to
Beijing.
- The received imagery will be displayed and put into the image
processing system for geometric correction and flood boundary
attraction. With the extracted boundary data, the losses caused by the
flood can be figured out by the flood-control database. Using the
analysing model in the database, which has an important role to play in
flood-control planning, regulating and preview, we can make greater
contributions to our country in this field.
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