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Volume 52 Supplement 10

Special Issue: Application of GPS and other space geodetic techniques to Earth Sciences (1)

Low-cost densification of permanent GPS networks for natural hazard mitigation: First tests on GSI’s GEONET network


Researchers from The University of New South Wales (UNSW), Australia, and from the Geographical Survey Institute (GSI), Japan, have commenced a joint project to develop, deploy and test an innovative hardware/software system design for an automatic, continuously-operated ground deformation monitoring system based on low-cost GPS receiver technology. Conventional continuously-operated GPS (CGPS) networks, such as the one established in Japan by GSI to precisely measure earth surface movement, are very expensive. The high cost being primarily due to the fact that dual-frequency receivers are used. Japan’s nationwide GEONET network is the world’s largest, numbering nearly 1000 receiver stations, with an average station spacing of the order of 30 km. In order to densify such CGPS networks (important when high spatial resolution for the monitoring of the deformation phenomenon is required), and to promote the use of the CGPS technique in lesser developed countries, a significantly cheaper system architecture is needed. The proposed design is an integrated, dual-mode network consisting of low-cost, single-frequency GPS receivers across the area of interest, surrounded by a sparser network of dual-frequency GPS receivers. Initial tests of data collected at selected stations in the GEONET network have already shown that through enhanced data processing algorithms a CGPS network containing both single-frequency and dual-frequency receivers would be able to deliver better than centimetre level accuracies, at considerably lower cost than present systems based exclusively on dual-frequency instrumentation. This paper reports the results of the first field test of this new CGPS system design, in the Tsukuba area of Japan, in August 1999. The test network consisted of: (a) several stations of the GEONET network surrounding (b) an inner network of four single-frequency Canadian Marconi GPS receivers installed by UNSW researchers. The data from both the GEONET and the UNSW receivers were processed using a specially modified version of the Bernese GPS Software Package. The software first processes the GEONET GPS station data in order to generate empirical corrections which are then applied to the double-differenced data of the GPS baselines located within the test area enclosed by the dual-frequency CGPS stations. These corrections have the effect of improving baseline solution accuracy by up to an order of magnitude, even for baselines ranging up to 100 km in length. The baselines connecting the inner network to the surrounding GEONET stations are processed in a number of modes, including 24 hr files (as is the standard practice for geodynamic applications) and hourly data files (as in volcano deformation monitoring applications). The results indicate that single-frequency-with-correction processing can achieve accuracies of better than 5 mm in the horizontal components and 3 cm in height, while the dual-frequency results can achieve accuracies better than 2 mm in the horizontal components and 6 mm in height. In the authors’ opinion, for certain geodynamic applications there are no significant differences between the single-frequency-with-correction results and the dual-frequency results, especially for the horizontal components.


  1. Chen, H. Y., C. Rizos, and S. Han, Rapid static medium-range GPS positioning techniques for geodynamic applications, 4th International Symp. on Satellite Navigation Technology and Applications, Brisbane, Australia, 20–23 July, paper 49, 12 pp., 1999.

  2. Ge, L., S. Han, and C. Rizos, Interpolation of GPS results incorporating geophysical and InSAR information, Pres. International Symposium on GPS—Application to Earth Sciences and Interaction with Other Space Geodetic Techniques, Tsukuba, Japan, 18–22 October, 1999.

  3. Han, S., Carrier phase-based long-range GPS kinematic positioning, Ph.D. Dissertation, UNISURV S-49, School of Geomatic Engineering, The University of New South Wales, Sydney, Australia, 185 pp., 1997.

  4. Han, S. and C. Rizos, GPS network design and error mitigation for realtime continuous array monitoring systems, 9th Int. Tech. Meeting of the Satellite Division of the U.S. Inst. of Navigation GPS ION ’96, Kansas City, Missouri, 17–20 September, 1827–1836, 1996.

  5. Rizos, C., S. Han, and H.-Y. Chen, Carrier phase-based, medium-range, GPS rapid static positioning in support of geodetic applications: algorithms and experimental results, Spatial Information Science and Technology Symp., Wuhan, P.R. China, 13–16 December, 7–16, 1998.

  6. Wu, J. T., Weighted differential GPS method for reducing ephemeris error, Manuscripta Geodaetica, 20, 1–7, 1994.

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Correspondence to Chris Rizos.

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Rizos, C., Han, S., Ge, L. et al. Low-cost densification of permanent GPS networks for natural hazard mitigation: First tests on GSI’s GEONET network. Earth Planet Sp 52, 867–871 (2000).

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  • Geographical Survey Institute
  • Average Station Spacing
  • GEONET Station
  • Centimetre Level Accuracy
  • Geodynamic Application