GPS 10, GPS , GPS. (J PL ) Zumbeger. mm, cm ; ( Global RT K) [3 ]

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1 27 3 Vol. 27 No Geomatics and Information Science of Wuhan University J une 2002 : X(2002) :A GPS 1 2 (1,,430072) (2 GPS,129,430079) : ; IGS IGS,,, 15min, X Y Z 20cm : GPS ;; : P , GPS,, GPS, GPS,,,,,, ns,,,,, GPS? 1997, (J PL ) Zumbeger, mm, cm ; 8cm,20cm [1,2 ], Hatch J PL, 10cm ( Global RT K) [3 ], ITRF,, 1 GPS ( P ) cm, m, 10m ( P 3m), IGS,, dm cm ( GPS ), : ; cm ; ns ;, :

2 3 : GPS 235,, IGS 35cm, IGS, IGS,, ( IGS ), 1. 1,, : v j p ( i) = j ( i) + c t ( i) + j trop ( i) - v j ( i) P j ( i) + p (1) = j ( i) + c t ( i) + j trop ( i) + N j ( i) - j ( i) + (2), j ; i ; c ; t ( i) ; j trop ; p ; P j ( i) j ( i) i, 1. 2,, GPS, IGS, GPS,,,,, 1 1 / m Tab. 1 The Satellites Antenna Phase Center Offset in Satellite Fixed Reference Frame/ m X Y Z Block II/ IIA Block IIR , v j p ( i) v ( j i), ; ( i) ; N j ( i) (1) (2) : ( ),,,, 0. 5d V ( i) = AX( i) + L ( i) (3) 1d GPS, X( i) = [ x y z t trop N j ] T (4) ( < 100km),, A ; L ( i) ; X ( i) ; x y z ; t km, cm,,, ; trop ; N j 30cm, 5cm,, j = 1,2,, n , ;,, ;,, m 24h cm,, m, ; 24h cm, Saastamonen,,, ( > 1 000km) [4 ]

3 :, ; 15min,, 30s,IGS GPS 30s ; 2. 2,, , GPS, Blewitt P [5 ] GPS 1) Melbourne- W bbena : L 6 ( i) = 1 f 1 - f 2 ( f 1 L 1 ( i) - f 2 L 2 ( i) ) - 1 f 1 + f 2 ( f 1 P 1 ( i) + f 2 P 2 ( i) ) (5) b 6 ( i) = L 6 ( i) ( f 1 - f 2 ) / c (6), L 1 L 2, L 1 = 1 1, L 2 = 2 2 ; i ; f 1 f 2 L 1 L 2 ; P 1 P 2 P ; b 6 2) Geometry-free : (a) X (b) Y (c) Z 1 X Y Z Fig. 1 The Differences in X, Y, Z Components between the Results Computed with Smoothed Code Observations and ITRF Coordinates

4 3 : GPS 237 L 4 ( i) = L 1 ( i) - L 2 ( i) = I + 1 n 1-2 n 2 (7) P 4 ( i) = P 1 ( i) - P 2 ( i) (8), 1 2 L 1 L 2 ; n 1 n 2 L 1 L 2 Melbourne- W bbena,, Melbourne- W bbena RMS 0. 5 (43cm),,b 6 : < b 6 > i = < b 6 > i i ( b 6 ( i) - < b 6 > i - 1 ) 2 i = 2 i i (9) 2 b 6 ( i) - < b 6 > i i - 1 (10) b 6,,,, b 6,, b 6, b 6 L 1 L 2 : b 6 = n 1 - n 2 (11), n 1 n 2 L 1 L 2 Melbourne- W bbena b 6,, Geometry-free N, N,, 1 n 1-2 n 2 (a) X (b) Y (c) Z 2 X Y Z Fig. 2 Precise Point Positioning Solution Convergence in X, Y, Z Component

5 (11), n 1 n dm,, P,, cm ,,, 2. 3, IGS, IGS KO KB d,,,, P 1m, 0. 01, IGS KO KB ITRF, 1 X Y Z ; 2 X Y (a) X (b) Y (c) Z 3 X Y Z Fig. 3 The Differences in X, Y, Z Component of the Results Computed with Undifferenced Phase Observations and ITRF Coordinates

6 3 : GPS Fig. 4 The RMS of the Results Computed with Undifferenced Phase Observations Z ; 3 X Y Z 1, m,,,,,,,,,, 15min,, X Y Z 20cm, X Y Z m m m 4, 2 0cm 3,,,,, 3, P GPS,, GPS,,, X Y Z 20cm,,,,, ( ),, 1 Zumberge J F, Heflin M B,Jefferson D C,et al. Precise Point Positioning for the Efficient and Robust Analysis of GPS Data from Large Networks. Journal of Geophysical Research,1997,102(B3) : Zumberge J F,Watkins M M,Webb F H. Characteristics and Application of Precise GPS Clock Solution Every 30 Seconds. Navigation,1998,44(4) : Hatch R. Satellite Navigation Accuracy : Past, Present and Future. Proceeding of the 8th GNSS Workshop, Ko2 rea, Heroux P, Kouba J, Collins P,et al. GPS Carrier-phase Point Positioning with Precise Orbit Products. The Inter2 national Symposium on Kinematic Systems in Geodesy, Geomatics and Navigation,Calgary, Blewitt G. An Automatic Editing Algorithm for GPS Da2 ta. Geophysical Research Letters,1990,17(3) : :,,, : GPS ; GPS ; WADGPS ; GPS E- mail edu. cn

7 GPS Precise Point Positioning Using Undifferenced Phase Observation L IU Jingnan 1 Y E S hi rong 2 (1 Presidential Secretariat,Wuhan University,Luojia Hill,Wuhan,China,430079) (2 GPS Research Center,Wuhan University,129 Luoyu Road,Wuhan,China,430079) Abstract :To overcome t hese shortcomings in differential GPS positioning,a new technique called precise point positioning ( PPP) has been developed. In this approach,the IGS precise orbits and satellite clocks are used toget her wit h t he undifferenced dual-f requency pseudorange and carrier p hase observations of one single receiver for precise geodetic point positioning. It provides a very efficient tool to access the terrestrial reference frame or L EO s orbit determination. Also it is the key technique to realize the Global RT K and the internet- based differential GPS positioning in the future. This paper describes the approach of PPP in detail,and then discusses some problems in data processing. Finally,it analyzes the experimental results,which show that the initial time of PPP is about 15 minutes and the accuracy of single epoch positioning can be better than 20cm in X, Y and Z component s after initialization. Key words :GPS ;precise point positioning ( PPP) ;undifferenced carrier p hase positioning About the author :LIU Jingnan,professor,Ph. D supervisor,member of the Chinese Academy of Engineering. His major research orientations in2 clude space geodesy and geodynamics. His typical achievements are the theory and scheme high precision GPS data processing in China ;the comprehensive software of GPS satellite positioning processing ;the software of WADGPS data processing ;the crustal movement and deforma2 tion of Qingzang Plateau using GPS,etc. edu. cn,sci EI, 1. :, 2. :,,,,,,, 8 000,, ,,, ( ) E- mail ( ) 3. :, ( ) ;, ; ;,, ;, 4. ( ) (ChinaInfo),, 5.,, 6. :129, ( ), , (027) E- mail edu. cn ; http :/ / www. wtusm. edu. cn ;http :/ / chinainfo. gov. cn/ periodical