1AOGS 2012, Singapore, Aug 13-17, 2012

Surveying co-located GNSS/VLBI/SLR Stations In

China

Xiuqiang Gong, Yunzhong Shen, Junping Chen, Bin Wu

Shanghai Astronomical Observatory

Tongji University

Email: xqgong@shao.ac.cn

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Content

Introduction

Surveying campaign

Data processing

Results and discussion

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Local tie

Local ties are necessary for establishment of ITRF

The Crustal Movement Observation

(CMONOC)Network of China

2000 GNSS stations,4 SLR stations and 7 VLBI stations

Local-ties missing and inconsistant

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GPS reference point

Measure the instrument height using calliper accurately

The ARP to RP(Antenna Phase Center)Phase center correction

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VLBI\SLR Reference PointDefined as intersection of the telescope axis or

invariant point when orientated. The constant distance from RP to the feed horn of the telescope is needed.

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SLR

VLBI

SLR/VLBI

Local ties of CMONOC

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Collecting data: control network

GNSS control network align vectors into the global frame. provide starting points for terrestrial control network

Terrestrial control network:get control points for SLR/VLBI

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Collecting data of circle

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Collecting data: Survey Methodology

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Data processing

GPS:Use Bernese5.2 and Gamit 10.35 to solve the

short baseline

Collect the coordinates of GNSS station of

ITRF2008

Non-constrain adjustment of GPS network

Combined terrestrial measurement adjustment:

Disatance

Direction

Vertical angle

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Model of 3D adjustment

2 2 2 /1000.ijS ij ij ij ij ijv S N E U a bS

Distance observation:in the station local coordinate frame

Where and mean Additive and Multiplication Constantba

2

0

tan'

'0

ij

ijiij N

ER

Direction observation:

2 2 2 2' ' ' tan ' '2ij

ij ij ij ij ij ij ij

KU E N V E N

R

Vertical angle observation：

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observational equations

j

j

j

ii

ij

ij

ij

Z

Y

X

LRBR

N

E

U

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Transfer the coordinates from the station local coordinate frame NEU to space reference system XYZ

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Results and comparison

Vector ∆X ∆Y ∆Z ∆N ∆E ∆U

CHAN-SLR -0.0015 -0.0067 -0.0128-0.0061 0.0052 -0.0121

GUAO-VLBI -0.0039 0.0059 -0.0036 -0.0065 0.0041 0.0016

SHAO-SLR -0.0014 -0.0040 -0.0006 0.0009 0.0032 0.0026

SHAO-VLBI 0.0059 -0.0048 -0.00120.0023 -0.0026 -0.0069

BJFS-SLR -0.0021 0.0060 0.0078 0.0020 -0.0007 0.0098

KUNM-SLR -0.0337 0.1197 -0.0029 0.0551 0.0063 0.1113

WUHN-SLR -0.0070 -0.0257 0.0279 -0.0344 -0.0168 0.0035

Comparison of our result with the ITRF2008 solution Value( in m)

The difference of Kunming is more than 10cm ， perhaps the instruments has been moved, or the SLR coordinate in ITRF2008 is not correct since it has few even none laser observations in these years.

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Results and comparison

Vector ∆X ∆Y ∆Z ∆N ∆E ∆U

GPS(SHAO)-VLBI 0.0100 -0.0174 -0.0102 0.0016 0.0005 -0.0224

GPS(WUHN)-SLR 0.0025 0.0089 0.0056 0.0012 -0.0059 0.0089

GPS(BJFS)-SLR 0.0004 0.0004 0.0045 -0.0035 -0.0005 -0.0027

Comparison of our results with IGN’S in 2003(value in m)

1 The two sets of results of BJFS site are in perfect agreement with the difference less than 5mm

2 The Wuhn site also has a good agreement since the distance is 13km.

3 The difference in Shanghai is huge especially in the height coordinate up to -2.24.

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Results and comparison

Comparison of the baseline difference between ITFR2008 and ITRF2000(value in m)

Vector ∆X ∆Y ∆Z ∆N ∆E ∆U

GPS-VLBI 0.0031 -0.0110 -0.0145 -0.0067 0.0030 -0.0169

Compare the results in ITRF2008 product and ITRF2000 ， the difference in U direction is up to -1.69. Considering this ， the differences of IGN’s result and our result are only 5.5mm.

Being a conclusion, we discover the fact that from 2003 up to 2011,the VLBI RP has descended about 2cm relative to the GPS RP in Shanghai where the two techniques are set in one courtyard.

So it is necessary that the co-location sites especially including VLBI telescope in China should be periodically re-measured on a regular basis.

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Thank you for your attention!