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IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 1
An Accurate High-Order Errors Suppression and
Cancellation Method for High-Precision
Airborne POS
Zhuangsheng Zhu , Member, IEEE, Chi Li, and Xiangyang Zhou
Abstract— Synthetic aperture radar imaging requires precise
position information provided by position and orientation system
(POS), especially sensitive to high-order errors of position infor-
mation, whereas high-order errors of global positioning system
(GPS) are normally ignored in POS solution procedure. For
high-precision POS, high-order errors become a significant error
source with decisive effects on the accuracy of POS. In this paper,
we propose a GPS high-order position errors suppression and
cancellation method, which includes the traditional GPS/inertia
navigation system (INS) integrated method used as the high-
frequency filter, and the low-frequency filter is based on least
squares support vector machine. The high- and low-frequency
dual filters are constructed to suppress and eliminate high-order
error. In verifying our dual-rate hybrid filtering method, POS
flight experiments were conducted in November and October up
to December in 2015, with results showing that the high-order
position accuracy of high-precision POS (0.01°/h gyro drift) is
better than 0.006 m, and the proposed method has a better
performance compared with other methods.
Index Terms— Global positioning system (GPS)/inertia
navigation system (INS), high-order error, motion compensation,
position and orientation system (POS), synthetic aperture
radar (SAR).
I. INT RODUCTION
S
YNTHETIC aperture radar (SAR) is an active remote
sensing equipment, which can be observed on the ground
at any time of the day in any weather conditions, and has the
ability of penetrating some observation objects. These features
give SAR its unique advantages in the military and civilian
applications, which is an important development direction of
airborne earth observation system [1]. SAR imaging requires
the antenna phase center (APC) of the state of motion for
uniform linear motion; however, the flight platform is affected
Manuscript received August 4, 2017; revised January 2, 2018; accepted
March 7, 2018. This work was supported in part by the National Nature
Science Foundation of China under Grant 61573040, Grant 61421063,
Grant 61571030, Grant 61473020, and Grant 61661136007, in part by the
National High Technology Research and Development Program of China
(863 Program) under Grant 2015AA124001 and Grant 2015AA124002, in part
by the Most Major Scientific Equipment Special of China under Grant
2012YQ160185, and in part by the Beijing Science and Technology Plan under
Grant D161100005816001 and Grant D171100006217003. (Corresponding
authors: Zhuangsheng Zhu; Xiangyang Zhou.)
The authors are with the Science and Technology on Inertial Laboratory,
Key Laboratory of Fundamental Science for National Defense—Novel Inertial
Instrument and Navigation System Technology, Beihang University, Beijing
100191, China (e-mail: zszhu@buaa.edu.cn; xyzhou@buaa.edu.cn).
Color versions of one or more of the figures in this paper are available
online at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/TGRS.2018.2815079
by external environment (such as air turbulence), internal
environment (such as engine vibration), and navigation flight
control system errors, which can lead to a complex, mul-
timode, and nonideal motion of the flight platform. As a
result, APC has motion errors that cause SAR imaging to
blur, defocus, deform, and even fail to obtain image [2], [3].
Therefore, in order to obtain high-resolution SAR images,
the consistency among time domain, spatial domain, and
spectral domain must be solved. The compensation of high-
precision motion error is to eliminate the motion error of APC
as much as possible [4], [5].
The SAR’s APC position and attitude information are given
directly by inertial measurement technology, and it is an
effective technical means to realize motion error compen-
sation [6], [7]. In the early stage, the navigation data of
the main inertial navigation system were directly used, but
it was far away from the APC, so the motion state of the
APC could not be measured realistically. Therefore, a special
inertial measurement unit (IMU) is developed, which can be
placed directly behind the SAR’s antenna, and the motion
error of APC can be measured more accurately. In addition,
the inertial measurement technology has accumulated error in
its inherent characteristics; therefore, it is now widely used
by motion compensation scheme b ased on global positioning
system (GPS)/IMU integrated measurement solution ensuring
the long-term accuracy of the system. As a result, POS has
been developed and applied to the airborne earth observation
system.
From the overall architecture of POS, which cannot be
separated from GPS, it is necessary to use the location and
speed information of GPS to correct the accumulated error
of inertial system. However, in the course of aviation flight,
high-frequency/high-order errors of GPS are introduced by
many factors, for example, GPS multipath [8], electromagnetic
interference and large angle maneuver of aircraft can cause
anomalies and fluctuations of GPS measurement noise [9],
and ionosphere model errors and troposphere model errors
in GPS systems [12]; they can be suppressed and eliminated
by differential GPS (DGPS) or real-time kinematic (RTK),
but the average coverage of the DGPS or RTK is only
20 ∼ 50 km; and the high-frequency/high-order errors are
the inherent characteristic of GPS information.
In addition, the airborne SAR motion error compensation is
mainly concerned with the high-frequency error and the high-
order error in a short period of time within a few seconds
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