Airborne Attitude Determination and Ground

Target Location Using GPS Information and

Vision Technique

Shan-Chih Hsieh, Luke K.Wang, Yean-Nong Yang†,Fei-Bin Hsaio*, Fan-Jen Tsai

Dept. of Electrical Engineering,National Kaohsiung University of Applied Sciences†Dept. of Electronic Engineering, National I-Lan Institute of Technology

*Institute of Aeronautics and Astronautics, National Cheng Kung University

OVERVIEW

1.INTRODUCTION

2.THE GPS SYSTEM

3.THE GPS-VISION SYSTEM

4.SIMULATION

5.SUMMARY

1.INTRODUCTION

•Sensor fusion method(vision+GPS+INS,or gyros)

•Vision-based navigation

•Focus of expansion(FOE)

•Attitude determination

GPS

Wabba problem

Least-squares

•Rotation representation

2.1The Homogeneous Transformation

CZCYCX

CTb

bTe

Z

Y

X

{b}:body coordinate

{e}:ECEF

{C}:camera coordinate

{C} -----> {e}

(2.1-1)

10000

0

0

Z

YeRb

X

eTb

For our case,

(2.1-2)

bRe: attitude of aircraft with respect to {e}

[X0 Y0 Z0]T :origin of the body frame.

2.2The Kinematic Equation

Quaternion: q = [q0 q1 q2 q3 ]T

Kinematics: qq

2

1(2.2-1)

0

0

0

0

123

132

231

321

www

www

www

www

q <--->R(q)

.

)(2)(2

)(2)(2

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3

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1

2

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2

3

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03021

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2

3

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qqqqqqqqqqqq

qqqqqqqqqqqq

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qR

{b}

GPS antenna

{C}

Earth

Target

{e}

Figure 1.The illustration of the imaging geometry and target location

3.THE GPS-VISION SYSTEMSystem: (1)a GPS pseudorange receiver

(2)a CCD camera

3.1The Monocular Vision System

Perspective projection:C

C

Z

Xfi 0

C

C

Z

Yfj 0

3.2The Kalman Filter Formulation

kkk dxfx )(1

kkk vxhZ )(

whereTT

kPosT

kqT

kw

kx

1011111

State:

Linearization:kkkk dxFx 1

kkkk vxHZ

where.

33430330

340

123

132

231

321

22

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11

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012

103

230

321

I

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I

x

f(x)F

qqq

qqq

qqq

qqq

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131231

0 0

0)(TT

TT

HH

HHf

x

xhH

3.3The Problem Formulation for Identification of Target Location

Q:Given (1)a sequence of noisy measurement of ground target (2)a sequence of time-tagged GPS measurement of aircraft

body coordinate

Solve:(1)WGS-84 coordinate of ground target

(2)aircraft’s attitude

4.SIMULATION

Aircraft maneuver:

pitch rate=0.001 grad.

Translate with constant velocity

measurement noise covariance: diag[10 m2 0.01 pixel2]

Ground target:stationary with an unknown WGS-84 coordinate

Target loci in image plane

The estimated attitude

The estimated target location

The estimated errors of ground target location

5.SUMMARY

Key features:

•Using only a single GPS pseudorange receiver to compute attitude

•Simultaneous determination of both ground target location and aircraft’s attitude

•Using EKF

Future Work

•Using Unscented Kalman Filter

•Using Particle Filter

•Using sophisticated camera model instead of pinhole model

Comments and Suggestions: