beidou status

Satellite Navigation Seminar > TUM > 14 May 2013

Slide 1

From China with Love*) The BeiDou Navigation System

O. Montenbruck(1), P. Steigenberger(2), A. Hauschild(1)

(1)DLR/GSOC, Oberpfaffenhofen (2)TUM/IAPG, Munich

*) a modern spy story?


Slide 2

Contents

System Overview

End User Equipment

Tracking Network

Data Analysis

Orbit and Clock Determination

Navigation Message

Code Biases and Positioning


Slide 3

Space Segment

DongFangHong-3 (DFH-3) bus

1.8 x 2,2 x 2.5 m3

17 m width, 27 m2

1.5 - 2 t dry mass

Orbits

MEO (12h53m; 13 rev in 7d)

GEO

IGSO (i=55)

Chinese and European Rb clocks

Laser retroreflector

2-way time transfer system (GEO)

C-band communication (GEO)


Slide 4

Constellation Status (Dec. 2012)

# Satellite Int. Sat. ID PRN Notes

1 M1 2007-011A C30 Suspected clock problems (Hauschild et al. 2012)

2 G2 2009-018A n/a Inactive; uncontrolled

3 G1 2010-001A C01 140.0 E

4 G3 2010-024A C03 110.5 (from 84.0 between Nov 7 and 22, 2012)

5 G4 2010-057A C04 160.0 E

6 I1 2010-036A C06 ~120 E

7 I2 2010-068A C07 ~120 E

8 I3 2011-013A C08 ~120 E

9 I4 2011-038A C09 ~95 E

10 I5 2011-073A C10 ~95 E

11 G5 2012-008A C05 58.75 E

12 M3 2012-018A C11

13 M4 2012-018B C12

14 M5 2012-050A C13

15 M6 2012-050B C14

16 G6 2012-059A C02 80.0E


Slide 5

Ground Tracks

BeiDou-capable monitoring stations (MGEX/CONGO/others)

1 May 2013


Slide 6

Signals

B1I/Q & B2I: BPSK(2), 2046 chips

B2Q & B3I/Q : BPSK(10), 10230 chips

B1I: Open Service ICD

B2I, B3I: known code generator structure

from high-gain antennas; inferred codes

L5 L2 L1 B1 B3 B2

E5a E5b E6 E2-L1-E1

GPS Galileo COMPASS

1176.450 MHz 1278.750 MHz 1575.420 MHz 1561.098 MHz 1268.520 MHz

1207.14 MHz 1227.60 MHz 1176.450 MHz f

(Thlert et al. 2010) (Stanford Univ.)


Slide 7

End User Equipment

Unicore UR240/260 (B1,B2,(B3))

Trimble NetR9 (B1,B2,B3) Septentrio AsteRx3 (B1,B2) Javad TriumphVS (B1,B2)

ComNav M300 (B1,B2)


Slide 8

Tracking Network (MGEX, CONGO, others)


Slide 9

Signal Strength

GMSD station (Trimble NetR9 and choke ring antenna) (GPS Solut (2013) 17:211222)

Wuhan (Unicore UB240 CORS) (Shi et al., GPS Solutions 17:103, 2013)


Slide 10

Code Noise and Multipath (Chennai)

Trimble NetR9 and

Zephyr antenna

Boresight angle

dependent multipath!?

(IGS WS 2012)


Slide 11

Triple-Carrier Combination

BeiDou (GEO)

QZSS

Difference of two ionosphere-free linear combinations

(GPS Solut (2013) 17:211222)


Slide 12

Phase Noise (Triple-Frequency Combination)

3F ~ 2.5 1F

(GPS Solut (2013) 17:211222)


Slide 13

BeiDou-Only Relative Positioning (Extra-Widelaning)

Curtin Univ. Perth (8 m Baseline)

(GPS Solut (2013) 17:211222)


Slide 14

Orbit Determination

(Only) 6 stations (spring 2012)

Bernese S/W

1-2 dm accuracy for IGSOs, 0.5-1 m for GEOs

SLR residuals 15-30 cm

Steigenberger et al. (2013) Orbit and clock

analysis of Compass GEO and IGSO

satellites, Journal of Geodesy

DOI 10.1007/s00190-013-0625-4


Slide 15

Clock Performance

Clock performance fully competitive with normal GNSS Rb clocks (but less than Rb-IIF and GAL-PHM)

(GPS Solut (2013) 17:211222)


Slide 16

Navigation Message D1 (MEO, IGSO)


Slide 17

Navigation Message D2 (GEO)


Slide 18

Broadcast Ephemeris Model

0

)sin(

)cos(

)()( ur

ur

i

z

y

x

xz RR

0

)sin(

)cos(

)()()5())(( 0 ur

ur

itt

z

y

x

xzxwz RRRR

D1 (MEO, IGSO)

D2 (GEO)

GM and differ

from GPS /

Galileo

Inclination w.r.t.

intermediate plane


Slide 19

Age of Data

MEOs

IGSOs

Uplink stations

only in China!?


Slide 20

Broadcast Orbit Accuracy SLR Residuals

Note: no antenna offset correction applied


Slide 21

Group Delays

)/(

DCB)/(

DCB

2B3

2B1B1

satrcvB3

B3B22B2

2B1B1

satrcvB2

B3B1B1satrcv

B1

ffITtctcP

ffITtctcP

ITtctcP

TGD1

?

Broadcast clock refers to B3 signal (not ionosphere-free B1/B2)!

Potential incompatibility of broadcast and precise clock products

Knowledge of DCBB2-B3 required for dual-frequency positioning

D1 SF1

TGD2 !


Slide 22

Differential Code Bias Determination

-15.0

-10.0

-5.0

0.0

5.0

10.0

15.0

C01 C02 C03 C04 C05 C06 C07 C08 C09 C10 C11 C12 C13 C14

DC

B B

1-B

3 [ns]

SIN1

CHEN

KZN2

CUTA

GMSD

TGD1-mean

-15.0

-10.0

-5.0

0.0

5.0

10.0

15.0

C01 C02 C03 C04 C05 C06 C07 C08 C09 C10 C11 C12 C13 C14

DC

B B

2-B

3 [

ns]

SING1 CHEN0

KZN23 CUTA1

GMSD1 TGD2-mean

DCB =

mean code difference after

GIM ionosphere correction


Slide 23

Single-Point Positioning with Broadcast Ephemeris

Single-frequency observations corrected with global ionosphere map

Best performance for B1-only positioning (TGDs?)

Station

(ID, Receiver)

GPS

L1

GPS

L1/L2

BDS

B1

BDS

B2

BDS

B3

BDS

B1/B2

BDS

B1/B3

PDOP

BDS

Singapore

(SIN1,NetR9)

E

N

U

3D

0.70 m

0.87 m

1.71 m

2.04 m

0.85m

0.59 m

2.04 m

2.29 m

0.78 m

0.98 m

2.16 m

2.50 m

0.89 m

1.35 m

3.50 m

3.86 m

0.90 m

1.22 m

3.52 m

3.83 m

1.36 m

0.93 m

2.34 m

2.86 m

1.14 m

1.13 m

3.13 m

3.52 m

1.9

Tanegashima

(GMSD,NetR9)

E

N

U

3D

0.86 m

1.24 m

3.09 m

3.44 m

0.80 m

0.99 m

2.01 m

2.38 m

0.90 m

1.28 m

3.06 m

3.44 m

1.03 m

1.78 m

3.98 m

4.48 m

1.07 m

1.59 m

3.90 m

4.34 m

1.43 m

1.57 m

4.32 m

4.81 m

1.66 m

1.89 m

3.95 m

4.68 m

2.6


Slide 24

Ionosphere Model

Standard model (all Satellites)

Provides TEC at ionospheric pierce point (in geographic long/lat)

Klobuchar-like model parameters (03, 03)

Updated 6x per day

Best accuracy for North Asia, GPS model preferrable for global use

SBAS data (GEO satellites)

Real-time ionospheric range delays (at B1)

6-min updates

Ionosphere Grid long 70..145 long, 10..55 and 7.552.5 latitude

Data confined to China mainland


Slide 25

Summary and Outlook

BeiDou is 3rd system to offer a (regional) standalone navigation service

User equipment readily available but limited amount of monitoring stations

Promising initial analysis and test results

Competitive system: 3 frequencies, good clocks, good broadcast ephemerides

ICD update should address dual-frequency use

IGS (MGEX) needs to incorporate BeiDou into product chain

Key spacecraft data (attitude, phase center) missing for precise processing

(When) will BeiDou switch to new GPS/GAL-like signals at L1/E1?

Will B3I remain unencrypted?

beidou status

Documents

beidou navigation system

f gps solut

b3 trimble netr9 b1

baseline gps solut

b2 javad triumphvs b1

b2 comnav m300 b1

gps solutions

choke ring antenna gps