Chapter 7 Summary, Conclusions, and Recommendations
7.3 Recommendations for Future Work
To further improve the geoid accuracy, there are several topics that need to be investigated in future work.
(1) New data for geoid modeling
The data used for the geoid computation has been increasing in recent years.
With regard to the local gravity data, more land, shipborne, and airborne gravity data measured over Taiwan and the surrounding seas will be acquired soon. We can further improve the geoid accuracy using these data. Besides the local gravity data, a high-resolution GGM, such as EGM06 coefficients, has been developed to degree 2190. It represents the earth potential more explicitly and provides more precise long-wavelength effects for geoid modeling. On the other hand, a 5-m resolution of the DEM over Taiwan is to be achieved by photogrammetry and LIDAR. This DEM is useful to refine the accuracy of the short-wavelength effects.
(2) 2D density model used in FFT and Gaussian quadrature
In chapter 4, a 2D density model was used only in the prism method. Its use in the FFT and Gaussian quadrature methods should be investigated.
(3) 3D density data
We considered only a 2D density when computing the RTM-derived effects.
Three-dimensional density data should fit in with the real topographic density variation
(4) Investigation of a more suitable covariance model
In this study, the Tscherning-Rapp degree variance model may not be suitable for the DWC of the direct geoid determination method. Other methods for constructing new covariance models should be investigated.
(5) Use of band-limited covariance function
The gravity data used in this study are from variety of sources. Unlike land gravity anomalies, most of the high-frequency gravity anomalies were removed from the original sources. Therefore, these gravity data are of limited spatial resolutions.
Therefore, a more rigorous method of geoid modeling than the method used in this study is to use band-limited covariance functions in LSC or band-limited kernel functions in the Stokes integral (Novak and Heck, 2002).
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Curriculum Vitae
Position:
Department of Civil Engineering National Chiao Tung University 1001 Ta Hsueh Road, Hsinchu 300 Taiwan
Phone: +886-3-5712121 ext 54990 Fax: +886-3-5716257
Email: [email protected] WWW: http://space.cv.nctu.edu.tw Date of Birth: December 20, 1977.
Place of birth: Tainan city, Taiwan.
Education:
BS, Dept of Surveying Engineering, National Cheng Kung University, June 2000.
MS, Dept of Civil Engineering, National Chiao Tung University, June 2002.
Major field of research:
Physical geodesy, Airborne gravimetry.
Publications:
Refereed journal papers
Hwang, C., C.S. Chen, J.T. Lee, C.G. Wang, L.H. Lee, Y.S. Hsiao, C.S. Cheng, and F.S. Ning (2002). Gravity survey on first-order benchmarks, Cadastre Survey, 21(1), pp.1-27. (in Chinese)
Hwang, C. and Y.S. Hsiao (2003). Orthometric correction from leveling, gravity, density and elevation data: a case study in Taiwan, Journal of Geodesy, 77, pp.
279-291.
Hwang, C., C.G. Wang, and Y.S. Hsiao (2003). Terrain correction computation using Gaussian quadrature: effect of innermost zone, Computers and Geosciences, 29 (10), pp. 1259-1268.
Hwang, C., Y.S. Hsiao, and T.L. Lin (2003). A digital elevation model of Taiwan and accuracy assessment, Cadastre Survey, 22 (2), pp.1-19. (in Chinese)
Hwang, C., Y.S. Hsiao, and H.C. Shih (2006) Data reduction in scalar airborne gravimetry: Theory, computer package and case study in Taiwan, Computers
Hwang, C., Y.S. Hsiao, C.C Lu, W.S. Wu, and Y.H. Tseng, (2007). Determination of Height of Northeast Asia’s Highest Peak (Mt. Jade) by direct leveling, Survey Review, 39 (303).
Hwang, C., Y.S. Hsiao, H.C. Shih, M. Yang, K.H., Chen, R. Forsberg, and A.V.
Olesen (2007b). Geodetic and geophysical results from a Taiwan airborne gravity survey: Data reduction and accuracy assessment, Journal of Geophysical Research, 112(B10), DOI:10.1029/2005JB004220.
Conference papers
Hwang, C., C.G. Wang, Y.S. Hsiao, T.C. Cheng, H.H. Wei, C.W. Lee, H.C. Yu, R.
Forsberg, and A.V. Olesen (2004). Absolute gravimetry and airborne gravimetry in Taiwan. Gravity, Geoid and Space Missions – GGSM2004, Porto, Portugal, August 30 – Sept. 3.
Hwang, C., C.G. Wang , Y.S. Hsiao, H.C. Shih, R. Forsberg, and A.V. Olesen (2005).
Results of airborne gravity survey in Taiwan, European Geosciences Union, General Assembly 2005, Vienna, Austria, 24 - 29 April.
Hwang, C., Y.S. Hsiao, H.C. Shih, C.G. Wang, R. Forsberg, and A.V. Olesen (2005).
Geodetic and geophysical results from a Taiwan airborne gravity survey, Dynamic Planet 2005, Cairns, Australia, 22-26 August.
Hsiao, Y.S., C. Hwang, and H.C. Shih (2006).Geoid modeling results over Taiwan using two different types of altimetry data, Western Pacific Geophysics Meeting, Beijing, China, 24-27 July.