Keywords: Remote Sensing.SAR.Computer
3D Simulation Technique.Scattering
Characteristics.Imaging Mechanism
Abstract As a kind of active microwave
remote sensing, Synthetic Aperture Radar has
become one of main directions of development
of remote sensing. Because SAR imaging
process overmuch depends on the sensor and the
scattering characteristics of ground object, it not
only brings us some limitations on obtaining
image, but also introduces errors into SAR
image during obtaining image process. These
problems will be discussed in this paper. We
firstly review the computer simulation technique
in remote sensing, the scattering characteristics
of ground objects and the SAR imaging
mechanism. Next, we propose the framework of
computer simulation SAR integrated system.
This system can produce dynamically SAR
images not only in various kinds of incident
angle.wavelength and polarimetric ways of
sensor, but also in different phases of ground
objects.vegetation variation. Using this system,
we can replace the field work, save time and
expenses, and avoid the risk aroused by wrong
decisions and operations.
1 Introduction
The development of remote sensing has come
into a new stage in the 1990s this century. As a
kind of active microwave remote sensing which
is one of important symbols in unprecedented
development of remote sensing, Synthetic
Aperture Radar has become one of main
directions of development of remote sensing.
SAR has unique advantages over the optical and
infrared sensor, which include high resolution.
round-the-clock work and the ability of
penetrating through soil and vegetation in certain
depth. Presently, SAR has important values in
monitoring disaster and environment.resources
investigation.ocean research.military scout and
survey scopes.
Now the researches for SAR mainly focus on
three aspects: 1. Sensor system and the imaging
system in the air; 2. The scattering characteristics
of ground objects; 3. Postprocession work in the
house including image processing and
information extraction.
Though SAR imaging has lots of advantages
over optical remote sensing, the imaging process
overmuch depend on the SAR sensor and the
scattering characteristics of ground object So
SAR provide us with images which are only
confined a certain wavelength.polarimetric ways
of sensor.time and special location et al. In
additional, due to the limitations of equipment
and processing techniques, most of operations
performed in the air during the a series of
processes from transmitting wave to producing
image will inevitably introduced unpredictable
system and random error into radar image For
example, transfer dissipative.aircraft motion
error and operation error will result in the
uncertainty of SAR image. These uncertain
information bring difficulties to image processing.
information extraction and the mechanism
research of remote sensing.
Whereas, we propose one kind of computer
simulation SAR system which integrates the
subsystem of sensor and imaging.the subsystem
of scattering characteristics of ground object and
the subsystem of information retrieval into one to
produce SAR simulation images using computer
completely, that is, the three subsystems are
implemented only using computer to simulate
their work situation in reality.
The direct goal of computer simulation SAR
system is to produce real time.dynamic images.
These images can be obtained not only in various
kinds of incident angle.wavelength and
polarimetric ways of sensor , but also in different
phases of object.vegetation change. The final
goals of this system are as follows: 1. Being
capable of grasping the difference of images
produced with different parameters(incident
angle.wavelength and polarimetric ways ) under
complex conditions. This predictability can help
the integrated system to choose optimal system
parameters(Shu,1997). 2. Being used in remote
sensing inversion, finding the law of scattering
characteristics of ground objects and establishing
the quantitative relationship between scattering
characteristics of ground objects and SAR image,
ultimately replacing field work completely. 3.
Saving time and money, and avoiding the risk
and needless expenses produced by wrong
decisions and operations. 4. Correcting the real
SAR image using the simulation SAR image at
the same area. 5. Helping us to know more the
detail of system, and know how the critical part
to effect the work status of whole system (for
example, regulating some system parameter and
observing how system to change).
In what follows, we first review the
development of computer simulation technique in
remote sensing. Next, the computer SAR
imaging mechanism is described. Then, the
image processing and the information extraction
for SAR simulation images are discussed. In
Section 5, we propose the basic approach of
realizing the computer simulation SAR integrated
system, and establish the integrated framework
for computer 3D simulation SAR system. The
conclusion remarks on computer 3D simulation
SAR system are presented in the final section.
2 The Feasibility Analysis of Computer
Simulation SAR
In this section, we mainly discuss the basic
environment for utilizing the computer
simulation SAR and the development status of
computer simulation SAR at the present time.
2.1 The Basic Environment
2.1.1 The development of techniques of obtaining
Remote Sensing information
In recent years, the Remote Sensing techniques
take high-speed development. Various sensors
existed include active sensors.passive sensors.
aircraft and satellite sensor.optical sensor.
infrared sensor and microwave sensor. Especially,
high resolution CCD sensor coming out and high
resolution commercial satellite blast-off in recent
years have provide lots of air-to-ground
information, so to speak, nearly arriving
“information explosion” (Chen et al, 1998).
2.1.2 Research of Mechanism of Remote Sensing and
Information Extraction
Object of remote sensing is the ground object. The
essence of the remote sensing is the problem of
inversion, that is, reasoning reversedly the geometry
and physics characteristics of ground objects through
microwave or light wave received (Chen,1998). For
using better remote sensing data, many scholars of
remote sensing devoted to the research of inversion of
remote sensing all the time, and have gained plentiful
achievements. Information extraction servers
application directly. Presently, the work can be
performed well by business software packages.
2.1.3 The Development of Computer 3D Simulation
Techniques
Simulation is the modeling of a part of the
world that we want to understand. A simulation
echoes the behavior of this real world system as it
changes from one state to another through time.
A computer simulation provides a tool for
studying real world systems in order to predict
their behavior under a variety of conditions
(Simulation Dynamics Inc. 1999). As the
computer graphics and calculating functions
become powerful gradually, computer 3D
simulation techniques with might redoubled have
come into the stage of application. For example,
military tactics manoeuvre.simulation tornado
and medicine expert directing surgery
scene ,even some games we often play.
2.2 The Development Status of Computer
Simulation SAR
In above section, we have mentioned that remote
sensing techniques.computer techniques and
simulation techniques have provided with abundant
resources for computer 3D simulation SAR system. In
this section, we mainly review computer 3D
simulation in remote sensing in the world at the
present time, which includes the simulation of
scattering characteristic of ground objects and the
simulation of remote sensing imaging.
2.2.1 The Simulation of Scattering Characteristic of
Ground Objects
We have above mentioned that the essence of
the remote sensing is to reason reversedly the
geometry and physics characteristics of ground
objects through microwave or light wave
received. BRDF and
s0 are attribute values to
embody the geometry and physics characteristics
of ground objects, nay are the important factors to
understand remote sensing and monitor the
vegetation canopy change. So it is fundamental
and important step to study BRDF and
s0.
As computer techniques developing at striking
speed, the method using computer simulation to gain
BRDF and
s0 like a new force suddenly rise has a
good prospect. This method is not only instead of lots
of field experiments in certain degree, but also a tool
to identify other simple.practical model. Next, we
introduce the research status of computer simulation at
the scattering characteristic of ground objects.
