Precise point positioning for the efficient and robust analy

精密单点定位最原始的论文,J. F. Zumberge,1997

JOURNAL OF GEOPHYSICAL

RESEARCH, VOL. 102, NO. B3, PAGES 5005-5017, MARCH 10, 1997

Precise point positioning for the efficient and robust analysis of GPS data from large networksJ. F. Zumberge, M. B. Heftin, D.C. Jefferson,M. M. Watkins,and F. H. WebbJet Propulsion Laboratory, California Institute of Technology,Pasadena

Abstract.

Networks of dozens to hundreds of permanently operating precision

Global Positioning System(GPS) receivers emerging spatialscales are at that range

from100to 10 km. To keep computational the burden associated the analysis withof such data economicallyfeasible, one approach is to first determine preciseGPS satellite positionsand clock correctionsfrom a globally distributed network of GPS receivers. Then, data from the local network are analyzed by estimating receiverspecific parameters with receiver-specificdata; satellite parameters are held fixed at their values determined in the global solution. This"precisepoint positioning" allows analysis of data from hundreds to thousandsof sites every day with 40Mfiop computers,with results comparable in quality to the simultaneousanalysis of all data. The referenceframesfor the global and network solutionscan be free of distortion imposed by erroneousfiducial constraintson any sites.Introduction

The Global PositioningSystem(GPS) has emergedin the 1990s as the space geodetic technique with the

The volume of GPS data is growing rapidly, and a means to analyze this volume in a consistent, robust,and economical manner is essential. In this article we

Heftin, 1995] plate-boundary deformation[Feiglet al., 1993], motion associated with earthquakes[Blewitt et al., 1993; Bock et al., 1993], and changingEarth orientation[Herring et al., 1991;Lindqwister al., 1992] etand rotation rate. More recent uses of GPS include

first discussthe computational burden associatedwith simultaneous virtues of accuracyand economy[e.g., processing GPS data in the 'contextof data volume and Yunck, 1995]. It has been applied to a variety of number of parameters estimated. We show that the geophysicalphenomena, including the motion of tec- computationalburden associated with the rigorousleast tonic plates[Larsonand Freymueller, 1995; Argusand squaresanalysisof data simultaneously from R receivers

scales with R3. To the extentthat globalparameters, that is, orbits of GPS satellites(expressed an Earthin fixed referenceframe) and satellite clocks,can be esti-

mated with a subset of the R receivers, then data from the others can be analyzed one at a time. Various analvolcanomonitoring[Webbet al., 1995], ground-based ysesof data from R= 49 receiversare used to quantify measurements atmospheric for[Busingeret al., 1996] the approximations involved in this technique, which and ionospheric[e.g., Wilsonet al., 1995]applications, we call"precisepoint positioning." The validity of the as well as atmosphere and ionosphere sounding[Mel- technique is also demonstrated based on data from over

bourne,1995] usinglow-Earth orbiters equippedwithreceivers.

GPS

102receivers 104stationdays. and

In heavily populated regionsof significantseismicac- Computational Burden tivity, deployment of dense networks of precisionGPS The two GPS data types,carrierphase(L) and pseureceiversis in progress. Already hundreds of receivers dorange(P), measurethe receiver-to-transmitter disare in operation in Japan and dozens in southern California. Networks suchas these allow the on-goingmea- tance with and without, respectively,an unknown bias. L is a much lessnoisy measurementthan P, which offsurement of the surface deformation field and are exsets the fact that it requires estimation of a bias term. pected to be valuable both in understandingthe complex systemof faults in the region and also in hazard Both data types exist at each of two frequencies,apmitigation. Additionally, space-basedarrays of GPS- proximately 1.2 and 1.6 GHz; this allows the formalinear combinationfor each, equipped receiversare expected over the next few years tion of the ionosphere-free which to first order is independentof the ionospheric to exploit the potential applications of GPS to climate, electron density. We assume in what follows that we weather, and the ionosphere.have formed this combinationand transmitter

for L and P.

A phase measurement at time t between receiver rCopyright 1997 by the American GeophysicalUnion.Paper number 96JB03860.x is modeled as

0148-0227/97/96 JB-03860509.005005

Lrxt+ Prxtb t+c t+ - , t+ C, t - z tm(O t) (1)+

精密单点定位最原始的论文,J. F. Zumberge,1997

5006

ZUMBERGE

ET AL.' PRECISE

POINT

POSITIONING

OF GPS DATA

where Prxt is the true range, brxt is the phase bias or

ambiguity,Zrt is the zenith tropospheric delay,m(Orxt) is the mappingfunction for elevationangleOrxtbetweenreceiver and transmitter, and OJrx is the phase windup t term to account for changesin the relative orientation

ters. It is approximately a factor of 2 slower than least squaresestimation using normal equations. The least squaresestimate of n parameters with ra measurementsrequires a number of arithmetic operations

of the receiving and transmittingantennas[Wu et al., 1993]. Receiverand transmitterclockcorrections areCrt and cxt, respectively. The term lYrx accounts for t

B (xn2m,

(5)

data noisein the measurement phaseto make (1) of an equality. A pseudorange measurementis similarlymodeled as

where the constant of proportionality dependson the choice of estimation algorithm but is of order unity

[Bierman,1977]. We neglect termsinvolving 3 and n nm because they are small comparedto n2m in this application.Thus (3), (4), and (5) give

Prxt - Prxt-}-Zrtm(Orxt) Crt - Cxtq-T]rxt, q-

(2)