Abstract

This paper summarizes the activities and achievements of the IAG Special Study Group (SSG) 3.167: "Regional Land and Marine Geoid Modelling", which was established by the XXIth General Assembly of IAG held in Boulder, Colorado, USA, July 3-14, 1995. The objectives of the SSG 3.167 reflects the duality between past and future and it consolidates what it has already been achieved, and works towards addressing open and new questions. The current state of knowledge in regional geoid modelling refers to: (a) theoretical models related to Boundary Value Problem (BVP) (e.g., how to include terrain and non-linear effects); (b) data reductions and data preparations; (c) modelling procedures for land and marine geoids; (d) accurate regional-scale marine geoid solution and their contribution to sea surface topography and other related oceanographic studies; and (e) validation procedures regarding the quality of the geoid product. Looking to open issues we could mention: (a) new efficient ways of working with heterogeneous data; (b) the impact of GPS - heights not only to validation procedures but also to common adjustments with geoid heights; (c) the study of compatibility of neighbouring datums through geoid determination; (d) the contribution of oceanography to synthetic geoid modelling and (e) new solutions of the global BVP, which can lead to better theoretical geoid models.

In terms of applications, and in the frame of the above mentioned main tasks, considerable work has been carried out in regional land and marine geoid modelling applying successfully efficient spectral and stochastic algorithms, as well as several new alternatives, and using large amounts of terrestrial and airborne gravity data, satellite altimetry data from recent and most accurate missions, and new global reference models.

1.  INTRODUCTION AND BACKGROUND

The modelling of the geoid in a regional scale is a traditional part of the activities of Section III (Determination of the gravity field) of IAG, and much has been achieved in this area, both as regards approximation and numerical methods and in results. That the interest of geoid modelling continues is due not only to its significance to practical geodetic surveying tasks and the needs of scientific investigations in other fields, but also because there remain unmet and new challenges within the topic itself, arising from new theoretical methods, new data sources, and new computational possibilities.

One of the reasons for the establishment of SSG 3.167 was, between others, the need of  theoretical research in the frame of the BVPs in the direction of computing regional-scale geoid solutions of high accuracy and resolution. Significant research was carried out in this topic during the life of our Study Group by some of its members and other individuals and since this research is still going on interesting results are expected both in terms of methodological procedures and in results as well. The open part of this kind of research is one of the major reasons that we strongly suggest the continuation of this SSG for the next four years.

The availability of vast amounts of terrestrial, airborne and satellite data sets, related to the gravity field, has also substantially contributed to the precise geoid determinations in different scales. Although there are difficulties in working across the land/sea divide (see paragraph 3), these data sets, e.g., from satellite altimetry and sea and land gravimetry gave the possibility to elaborate large data grids in the computers and to compute in one run geoid heights and other gravity field quantities over land/sea areas. This was also one of the main tasks of our group and many of its members concentrated their efforts on this target. More details for related specific accomplishments are given in paragraph 3.

During the past decade, spectral methods have been competing very favourably against the classical ones, showing almost the same level of accuracy but much higher efficiency. These methods and the fast algorithms (e.g., Fast Fourier Transform - FFT, Fast Hartley Transform - FHT) developed for computations using large gridded data sets, were improved in terms of three-dimensional computations, spherical approximation procedures, spectral computations in non-uniform grids. On the other hand, multiple-input output spectral relationships were developed to combine heterogeneous terrestrial, airborne and satellite altimetry data. Based on these methods significant progress was made in the study of isotropic and non-isotropic power spectral density functions, and the introduction of parametric models, especially for power spectrum estimation. Other methodologies were also developed for gravity field modelling, like wavelets and spectral algorithms in inverse problems, but these mainly belong to IAG Section IV and only some review papers will be referenced in paragraph 3. The traditional stochastic methods based on least-squares collocation procedures, were mainly used, the last years, to the common adjustment of different height sets and to the treatment of the residuals between gravimetric geoid heights and GPS-derived corresponding heights.

2.  SSG 3.167 - MEMBERS, TASKS AND GOALS

SSG 3.167 had twenty one regular members, including the president and eight corresponding members. The SSG started its activities after Boulder (July 3-14, 1995) under the chairmanship of Herman van Gysen. After the sad circumstance of Herman's death (February 19, 1998) I took over the chair of the SSG according to the relevant decision of the IAG Executive Committee. The names of the members of the SSG and countries are given on the following list:

PRESIDENT:

Herman van Gysen    (Canada)  from July 1995 to February 1998

Ilias N. Tziavos   (Greece) from February 1998 - today

MEMBERS:

O. Andersen (Denmark)

M. Kuhn (Germany)

R. Barzaghi (Italy)

J. Li (Canada)

D. Behrend (Germany)

C. Merry (South Africa)

W. Featherstone (Australia)

D. Milbert (USA)

R. Hipkin (United Kingdom)

E. de Min (The Netherlands)

Z. Jiang (France)

G. Papp (Hungary)

A.H.W. Kearsley  (Australia)

B. Shaofeng (China)

P. Knudsen (Denmark)

G.C. Tsuei (Taiwan)

J. Krynski (Poland)

M. Vermeer (Finland)

CORRESPONDING MEMBERS:

D. Blitzkow  (Brazil)

M. Pearse (N. Zealand)

M. Bouziane (Algeria)

M. Satomura (Japan)

H. Denker (Germany)

M.Sideris (Canada)

R. Forsberg (Denmark)

W. Wiezak (Poland)

After the meeting in Trieste (September 7-12, 1998) the following colleagues started to be informed on the activities of the SSG 3.167, acting, unofficially, as corresponding members: R. Haagmans (The Netherlands), Y. Fukuda (Japan) and V.D. Andritsanos (Greece).

The input of most of the above members in the frame of a "position paper" sent to the first President of the SSG together with the recommendations for further research resulted in the formation of the tasks and goals of SSG 3.167 which are outlined in the Objectives and Programme (http://tziavos@olimpia.topo.auth.gr) and are given below:

1. Extent of the various elements on regional geoid modelling; data reductions and data preparation (including data gridding and block averaging).

2. The use of theoretical models in regional geoid modelling with respect to terrain and non-linear effects.

3.The use of numerical techniques and the possibilities to prescribe or recommend the extent of a standard procedure.

4. Substantive differences between the modelling procedures for land and marine geoids and the difficulties in working across the land/sea divide.

5. Validation procedures and measures of quality of the geoid product.

6. Availability of regional geoids (maps, gridded heights, function coefficients, data compression techniques).

Looking to open questions the following questions present themselves:

1. What is the best way of working with heterogeneous data?

2. Are GPS-derived geoid heights forever to be relegated to a validation-only role? Are there new techniques for a common adjustment of GPS and geoid heights? What is the impact of GPS in studying the compatibility of neighbouring datums through geoid determination?

3. Are there new solutions of the GBVP that hold the promise of better theoretical geoid models?

4. Are there new approximation and numerical techniques that hold the promise of a closer representation or more efficient computation?

5. What is the contribution of an accurate regional-scale marine geoid solution on sea surface topography studies?

6. Are there lessons that geodesists can learn from the oceanographers' technique of 'synthetic' geoid modelling?

Specific accomplishments and suggestions for future research work related, mainly, to the above mentioned open questions are given in the next section. The members of the SSG 3.167 met informally during several international symposia held in the period of 1995 to 1999. More specifically, during the last one and half year we had two informal meetings in Budapest (March 1998) and Trieste (September 1998) in the frame of IAG Symposia. Although the Study Group, as a unit, was not engaged in any service activity, various members served or are still serving on national and international committees. Several members also have contributed to national and international geodetic agencies, industry and universities by providing them with softwares and different data sets.

 3. SPECIFIC ACCOMPLISHMENTS
The members of the Study Group concentrated their efforts mainly on tasks 1, 3, 4, 5, 6 tabulated in paragraph 2. Significant research work has been also carried out in the frame of the so called "open questions" (see paragraph 2) defined when establishing the main objectives of the Study Group. Although much progress has been made answering almost all of these questions, significant research is necessary to be done in the future in the frame of some of these topics, mentioned in the sequel as question 1, 2, etc. Some work was also done on theoretical problems (see Task 2) related to regional geoid or quasi-geoid modelling not only by members of the SSG 3.167 but also from colleagues who had a good connection with the group or have been acted as corresponding members of it. BVPs in different scales and the mixed altimetry-gravimetry problem investigating the choice of the best norm and the linearization of errors inherent in standard procedures were studied in the frame of gravity field modelling in general and in regional land and marine geoid approximation in particular (see, e.g., Sanso, 1997; Sanso and Rummel, 1997; Martinec and Grafarend, 1997; Martinec, 1998; Lehman, 1999; Holota, 1996, 1998, 1999; Vanicek et al., 1995; Vanicek and Featherstone, 1998; Zhang and Featherstone, 1997).

For Task 1, progress was made by the optimization of techniques for computing direct and indirect effects of the topography on geoid and gravity. Formulas in spherical approximations and in the frequency domain were developed and techniques were proposed based on kernels' modification in order to overcome singularity problems apparent in computations in very dense and mountainous terrains (Petrovic, 1996; Liu et al., 1997; Rosza, 1998; Toth, 1998; Tziavos and Andritsanos, 1998; Tsoulis, 1998; Dahl and Forsberg, 1999; Nahavandchi and Sjoberg, 1998a; Nahavandchi, 1999); very promising results were reported recently by Tsoulis (1999). The effects of density variations on terrain corrections and geoid determinations were studies by Tziavos et al. (1996), Kuhtreiber (1998), Martinec (1998). Denker and Tziavos (1998) studied the Molodensky correction terms, with emphasis on the use of different terrain reduction techniques. Maximum effects of the Molodensky series terms are 10 cm in mountainous areas and 1 cm for highland areas. The theory of height systems is discussed in several publications with regard to the combination with GPS ellipsoidal heights (Grafarend et al., 1996; Lelgemann and Petrovic, 1997; Grafarend and Okeke, 1998; Nahavandchi and Sjoberg, 1998b). The unification of different neighbouring or local height system is also investigated by several authors, as well as the contribution of gravimetric geoid solutions and GPS in the connection of neighbouring datums (Khafid, 1998; Pan and Sjoberg, 1998).

Several objectives of SSG 3.167 (see tasks 3, 4, 5, 6), which cover also the topics of Questions 1, 2, 4, 5 are directly connected with the analysis, processing and combination of large data sets available from (a) satellite altimetry of the high resolution geodetic missions of Geosat and ERS-1 and the most recent and accurate missions of TOPEX/Poseidon and ERS-2, (b) airborne gravimetry, (c) sea and terrestrial gravimetry, (d) GPS, (e) gravity gradients, (f) deflections of the vertical and (g) high resolution Digital Terrain Models (DTMs) and Digital Depth Models (DDMs). The optimal combinations of one or more of these data sources with a high degree and order geopotential model according to the well known remove-restore technique contribute to the high resolution and accuracy regional-scale geoid or quasi-geoid determinations (see, e.g., Denker and Torge, 1998; Torge and Denker, 1998; Ihde et al., 1998; Vermeer, 1998). Denker and Torge (1998) were evaluated the new revised version of the European Geoid EGG97 by a number of GPS/levelling data sets. The residuals showed medium to long wavelength features of a few cm/100 km and a few dm/1000 km. The long wavelength errors can be modelled by a trend and signal component using least squares collocation with an appropriate covariance function, as it is proposed by Denker (1998), Forsberg (1998), Kotsakis and Sideris (1998) and Duquenne (1999), while results from a combination of gravimetric geoid heights with heights from GPS/levelling and a geopotential model were carried out by Seeber and Torge (1997), Seeber et al. (1997), Duquenne (1996, 1999), Ihde et al. (1998). Interesting results were also reported by Milbert (1995), Sideris and She (1995), Pagiatakis (1996), Blitzkow et al. (1995, 1997) and Veronneau (1997a) with regard to the improvement of continental-scale and high resolution geoid height models. Various tests on geoid/quasi-geoid on GPS benchmarks confirmed the above mentioned accuracy levels and some authors, within the residuals, studied additionally, several systematic effects (Behrend et al., 1995; Verhoef et al., 1996; Jiang, 1996; Barbarella et al., 1998; Toth et al., 1998; Tsuei et al., 1998; Fukuda et al., 1997; Kenyeres, 1997; Duquenne, 1998; Ollikainen, 1998; Tziavos et al., 1998; Veronneau, 1997b; Basic et al., 1999). In Featherstone et al. (1998), Featherstone and Sideris (1998), Forsberg and Featherstone (1998), Vanicek and Featherstone (1998), Tziavos et al. (1998), Toth et al. (1998) the effects of different kernels modification and the limited cap-size on geoid height determination were extensively discussed.

Much progress was also made in terms of the improvement of methods widely used in physical geodesy during the last decade, as, e.g., the spectral techniques and the fast algorithms (FFT, FHT) developed for computing efficiently geoid and other components related to the gravity field, as well as terrain effects, on the surface of the earth and on level surfaces (Sideris, 1995; Tziavos, 1995; Denker et al., 1997; Forsberg, 1998; ). The outperformance of the 1D-FFT over the other spectral techniques in local and regional-scale geoid/quasi-geoid computations has been discussed by several authors (see, e.g., Sideris, 1995; Tziavos, 1995; Sideris and She, 1995; Li, 1996; Li and Sideris, 1997; Min, 1996a; 1996b). The use of Input/Output system theory (IOST) algorithms in the frequency domain were also used the last few years to combine heterogeneous data for regional geoid modelling in the frequency domain such overcoming one of the main advantages of the spectral methods (e.g., Sanso and Sideris, 1997; Sideris, 1995a; 1995b; Li, 1996; Tziavos et al., 1998b; 1998c; 1998d; 1998e; Kotsakis and Sideris, 1998). The IOST methods, very similar to least squares collocation method in the frequency domain, contributed also to error propagation studies and to the optimal treatment of noise-to-signal ratios of the different input data sets to the combination procedures, as was pointed out by Sideris (1995b), Tziavos et al. (1997), Tziavos et al. (1998c, 1998d). Refinements were performed by several authors in classical integral, least-squares collocation based methods, point mass representation algorithms and combinations of them, and the modified algorithms heve been used in geoid computation exapmles (see, e.g., Arabelos and Tscherning, 1998; Min, 1995; Tscherning et al., 1998; Vermeer, 1998).

Special emphasis was put on the combination of marine gravity data with altimeter sea surface heights, either using spectral or stochastic methods. The implication of altimeter derived gravity anomalies in such procedures available from global data bases (Andersen and Knudsen, 1998; Andersen et al., 1998; Sandwell and Smith, 1997) helped to fill gaps in sea areas, and contributed substantially to high accuracy and resolution marine geoid modelling. Hwang and Parsons (1997), Hwang (1998), Zhang (1998) were carried out promising results as regards of marine geoid and gravity computations over extended test areas using multi-resolution satellite altimetry and shipborne gravimetry. Kirby (1996) proposed a new spectral method for the optimal combination of altimeter heights with sea gravimetry and Behrend (1999) documented the above mentioned combination strategy based on the remove restore technique. Relevant results and marine geoid solutions on a regional scale were published by different authors (see, e.g., Hipkin, 1995; Olgiati et al., 1995; Li, 1996; Tziavos et al., 1996b; 1998b, 1998c, 1998d, 1998e; Rodriguez and Sevilla, 1999). Andersen and Knudsen (1999) discussed the role of satellite altimetry in gravity field modelling in coastal areas, combining marine, land, satellite and airborne observations. They also discussed the computation problems at the boundary (see/land) and proposed the use of an appropriate covariance function to enhance the spatial resolution. Hipkin (1999) performed an interesting analysis on the modelling of gravity, geoid and sea surface topography in coastal and self areas pointing out problems and possibilities.

Regional-scale geoid computations were presented by Milbert (1995), Milbert and Smith (1996), Smith and Milbert (1997), Smith and Small (1999), who gave also promising comparison results on GPS/levelling/tide benchmarks. Merry (1998) has been presented an interesting paper on a regional quasi-geoid determination for the South-Western Cape in South Africa and discussed the crucial role of such a geoid solution in transforming GPS-derived heights to normal heights. Papp et al. (1998) studied the geophysical dimension of a regional geoid approximation determining a lithospheric geoid solution for Hungary, Strykowski (1996) studied interesting inverse gravity models related to geophysical fields, Toth (1998), Toth et al. (1998) investigated correlations of regional gravimetric geoids with upper crust densities and other geophysical parameters.

National-scale geoid computations have been published by many authors and almost all these contributions are included in the Proceeding issues of IGeS (Bulletins No 4 and No 7) and Finnish Geodetic Institute and in the IAG and EGS Proceedings edited by (Tziavos and Vermeer, 1996; Sanso and Rummel, 1997; Segawa et al., 1997; Vermeer and Adam, 1998; Forsberg et al., 1998). Last, but definitely not least, it is worth mentioning here the interesting review paper by Vermeer (1998), who thoroughly studied the geoid/quasi-geoid as a final product and gave several other dimensions of it related to economic and ideological arguments.

As it is apparent from the analysis given in section 3, Members of the SSG and other colleagues, during the last four years, worked towards to address in its different targets and to identify the key issues of the open problems that remain to be tackled. Many important refinements have been made to the methods used to regional land and marine geoid modelling, and interesting results were reported in different publications. It is expected that further improvements and new applications will develop as a result of the research already done. It is suggested that special attention be paid and further investigation be done with respect to some of the open questions mentioned before:

- Theoretical and numerical work in land/sea regional geoid/quasi-geoid computations and mainly in applications at the boundary and self seas taking advantage from oceanographic information.

- The impact of GPS in studying the compatibility of neighbouring datums through regional geoid/quasi-geoid determination.

- Modelling of medium and long wavelength errors in regional geoid computations by the future dedicated gravity field missions (CHAMP, GRACE, GOCE, etc.).

- More accurate sea surface topography determinations by marine combined geoid solutions.

On the whole, it is recommended the work of SSG 3.167 to be continued for the next four years. The rich bibliography given below will provide the basis for tackling the new goals outlined above.

New geoids in the world. Special Issue of the International Association Geodesy, International Geoid Service (IGeS) Bulletin No 4, Bureau Gravimetrique International Bulletin d' Information No 77, 1995.

Techniques for local geoid determination. Proceedings, (Ilias N. Tziavos and Martin Vermeer eds.), Session G7 European Geophysical Society, XXI General Assembly, The Hague, The Netherlands, 6-10 May, 1996, publ. 96:2, Finnish Geodetic Institute, 1996.

Geodetic boundary value problems in view of the one centimeter geoid., (Fernando Sanso and Reiner Rummel eds.), Lecture Notes, 592 pp, Springer, 1997.

Gravity, Geoid and Marine Geodesy. Proceedings, (J. Segawa, H. Fujimoto and S. Okubo eds.), Tokyo, Japan, September 30 - October 5, 1996,  IAG Symposia vol. 117, publ. Springer, 1997.

The Earth Gravity Model EGM96: Testing procedures at IGeS. International Geoid Service (IGeS) Bulletin No 7, 1997.

Second Continental Workshop on the Geoid in Europe. Proceedings (Martin Vermeer and Jozsef Adam eds.), Budapest, Hungary, March 10-14, 1998, publ. 98:4, Finnish Geodetic Institute, 1998.

Geodesy on the Move - Gravity, Geoid, Geodynamics, and Antarctica, Proceedings (R. Forsberg, M. Feissel, R. Dietrich eds.), IAG Scientific Assembly, Rio de Janeiro, Sept. 3-9,  1997, IAG Symposia vol. 119, Springer, 1998.

Abd-Elmotaal, H. A.: Detailed gravimetric geoid for the Egyptian south-western desert. Phys. Chem. Earth, 23(1), 77-80, 1998.

Abd-Elmotaal, H. A.: Gravity reduction techniques and their comparisons applied to the gravity field in Egypt. Finnish Geodetic Institute Report 98:4, pp. 177-183. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Abd-Elmotaal, H.A.: An efficient technique for the computation of the gravimetric quantities from geopotential earth models. In: R. Forsberg et al. (Eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 182-187, Springer, 1998.

Abd-Elmotaal, H.A., N. Kuhtreiber: Improving the geoid by adapting the reference field. Phys. Chem. Earth (A), 24(1), 53-60, 1999.

Adjaout, A., M. Sarrailh: A new gravity map, a new marine geoid around Japan and the detection of the Kuroshio current. Journal of Geodesy, 71(12), 725-735, 1997.

Ahmad-Berger, Z., A.H.W. Kearsley: Geoid height optimization via sequential least squares method. In J. Segawa et al. (Eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 629-636, Springer, 1997.

Al Bayari, O., G. Bitelli, C. Bonini, A. Capra, D. Dominici, E. Ercolani, S. Gandolfi, A. Pellegrinelli, M. Unguendoli, L. Vittuari: A local geoid in the south-eastern Po Valley (ITALY). Finnish Geodetic Institute Report 96:2, pp. 157-164. Proceedings, Session G7, EGS XXI Gen. Assembly, The Hague, The Netherlands, 6-10 May, 1996.

Albertella, A., R. Barzaghi, F. Sanso, G.Sona: Geopotential models validation at EGS. IGeS Bulletin no 6, pp. 135-150, 1997.

Albertella, A., F. Sacerdote: Spectral analysis of block averaged data in geopotential global model determination. Journal of Geodesy, 70(3), 166-175, 1995.

Andersen, O., P. Knudsen: Global marine gravity field from the ERS-1 and Geosat geodetic mission altimetry. JGR, 103(C4), 8129-8137, 1998.

Andersen, O., P. Knudsen, S. Kenyon, R. Trimmer: Recent improvements in the KMS global marine gravity field. Proceed. 2nd Joint Meeting of the Int. Gravity Commission and the Int. Geoid Commission, Trieste, 7-12 Sept. 1998, in print.

Andersen, O., P. Knudsen: The role of satellite altimetry in gravity field modelling in coastal areas. Proceed. XXIV EGS Gen. Assembly, The Hague, 19-23 April, 1999, in print.

Andritsanos, V.D., D. Arabelos, S.D. Spatalas, I.N. Tziavos: Mean sea level studies in the Aegean Sea. Proceed. XXIV EGS Gen. Assembly, The Hague, 19-23 April, 1999, in print.

Arabelos, D., C. C. Tscherning: Gravity field recovery from airborne gradiometer data using collocation and taking into account correlated errors. Phys. Chem. Earth (A), 24(1), 19-26, 1999.

Arabelos, D., C.C. Tscherning: Calibration of satellite gradiometer data aided by ground gravity data. Journal of Geodesy, 72(11), 617-625, 1998.

Arabelos, D., C.C. Tscherning: Comparison of recent geopotential models with surface, airborne and satellite data in different areas of the earth.

Arabelos, D., C.C. Tscherning: The use of least square collocation method in the global gravity field modelling. Phys. Chem. Earth, 23(1), 1-12, 1998.

Arabelos, D., I.N. Tziavos (1996). Combination of ERS-1 and TOPEX altimetry for precise geoid and gravity recovery in the Mediterranean Sea. Geophys. J. Int., 125, 285-302.

Arabelos, D., I.N. Tziavos: Gravity-field improvement in the Mediterranean Sea by estimating the bottom topography using collocation. Journal of Geodesy, 72(3), 136-143, 1998.

Arabelos, D., C.C. Tscherning: Collocation with finite covariance functions. IGeS Bulletin no 5, pp. 117-135, 1996.

Arabelos, D., S. Spatalas, I. N. Tziavos, M. Sevilla, J. Catalao: Geoid and tidal studies in the Mediterranean Sea. Finnish Geodetic Institute Report 96:2, pp. 175-180. Proceedings, Session G7, EGS XXI Gen. Assembly, The Hague, The Netherlands, 6-10 May, 1996.

Ayhan, M.E.: Updating and computing the geoid using two dimensional fast Hartley transform and fast T transform. Journal of Geodesy, 71(6), 362-369, 1997.

Auzinger, T., W.-D. Schuh: High-degree spherical harmonic analysis combining gridded and random distributed data sets. Phys. Chem. Earth, 23(1), 19-24, 1998.

Banerjee, P., G.R. Foulger, Satyaprakash, C.P. Dabrai: Geoid undulation modelling and interpretation at Ladak, NW Himalaya using GPS and levelling data. Journal of Geodesy, 73(2), 79-86, 1999.

Barbarela, M., R. Barzaghi, D. Dominici, M. Fiani, S. Gandolfi, G. Sona: A comparison between Italgeo '95 and GPS/Levelling data along the coasts of Italy. Phys. Chem. Earth, 23(1), 81-86, 1998.

Barzaghi, R., A. Borghi: The definition of a regional geopotential model for precise gravity field modelling. IGeS Bulletin no 7, pp. 52-67, 1995.

Barzaghi, R., M. A. Brovelli, G. Sona, A. Manzino, D. Sguerso: The new Italian quasigeoid: ITALGEO95. Finnish Geodetic Institute Report 96:2, pp. 111-120. Proceedings, Session G7, EGS XXI Gen. Assembly, The Hague, The Netherlands, 6-10 May, 1996.

Barzaghi, R., M.A. Brovelli, G. Sona, A. Manzino, D. Sguerso: The new Italian quasigeoid: ITALGEO95.  IAG, Bulletin d' Information no 77, IGeS Bulletin no 4, pp. 137-152, 1995.

Basic, T., M. Brkic, H. Sunkel: A new, more accurate geoid for Croatia. Phys. Chem. Earth (A), 24(1), 67-72, 1999.

Behrend, D., H. Denker, W. Torge: Gravity field determination in the German Bight (North Sea). Pres. Paper, XXI IUGG General Assembly, Boulder, Colorado, U.S.A., July 2-14, 1995.

Behrend, D.: Untersuchungen zur Schwerefeldbestimmung in den europ_ischen Randmeeren. Wiss. Arb. D. Fachr. Verm.wesen d. Univ. Hannover (Diss.), Nr. 229, 1999.

Belikov, M.V., E. Groten: An attempt to construct the precise gravimetric geoid in Germany. Allg. Verm.nachr., 305-309, 1995.

Benaim, E. H., A. M. Swassi, M. Sevilla: The first Northern Moroccan gravimetric geoid. Phys. Chem. Earth, 23(1), 65-70, 1998.

Berrocoso, M., J. Garate, J. Martin, A. Fernandez, G. Moreu, B. Jigena: Improving the local geoid with GPS. Finish Geodetic Institute Report 96:2, pp. 91-96. Proceedings, Session G7, EGS XXI Gen. Assembly, The Hague, The Netherlands, 6-10 May, 1996.

Birardi, G., D. Santarsiero, D. Tufillaro, L. Surace: Setting-up local "mapping geoids" with the aid of GPS/LEV traverses. Applications to the geoids of Sardinia and Calabria. Journal of Geodesy, 70(1-2), 98-109, 1995.

Blais, J.A.R.: Spectrum estimation using maximum entropy and multiresolution considerations. Journal of Geodesy, 70(6), 349-356, 1995.

Blitzkov, D.: NASA(GSFC) / NIMA Model evaluation. IGeS Bulletin no 6, pp. 47-70, 1997.

Blitzkow, D., J.D. Fairhead, M.C. Lobianco: A preliminary gravimetric geoid for South America. IAG, Bulletin d' Information no 77, IGeS Bulletin no 4, pp. 53-66, 1995.

Blitzkow, D., M.C.B. Lobianco, J.D. Fairhead: Data coverage improvement for geoid computation in South America. In J. Segawa et al. (Eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 523-531, Springer, 1997.

Biltzkow, D.: Toward 10' resolution geoid for South America: a comparison study. Phys. Chem. Earth (A), 24(1), 33-40, 1999.

Bouman, J., R. Koop: Regularization in gradiometric analysis. Phys. Chem. Earth, 23(1), 41-46, 1998.

Bouziane, M.: The new Algerian quasi-geoid 96 computed using spherical FFT. IGeS Bulletin no 5, pp. 40-56, 1996.

Bursa, M., J. Kouba, A. Muller, K. Radej, S. A. True, V. Vatrt, M. Vojtiskova: Accuracy estimates of EGM96 geoid with emphasis on central Europe, Scandinavia and Baltic region. Finnish Geodetic Institute Report 98:4, pp. 81-85. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Bursa, M., K. Radej, Z. Sima, S.A. True, V. Vatrt: Tests for accuracy of recent geopotential models. IGeS Bulletin no 6, pp. 167-188, 1997.

Catalao, J.C., M.J. Sevilla: Geoid studies in the north-east Atlantic. In: R. Forsberg et al. (Eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 269-274, Springer, 1998.

Chen, J., J. Li, J. Ning, D. Chao: testing and evaluation of the GSFC/DMA EGM in China. IGeS Bulletin no 6, pp. 189-202, 1997.

Chen, Junyong: Accuracy evaluation of the height anomaly prediction by means of gravity data in a height anomaly control network. IAG, Bulletin d' Information no 77, IGeS Bulletin no 4, pp. 67-76, 1995.

Chuanding, Z., L. Zhonglian, W. Xiaoping: Truncation error formulae for the disturbing gravity vector. Journal of Geodesy, 72(3), 119-123, 1998.

Colic, K., B. Pribicevic, D. Svehla: First cm-geoid in the Republic of Croatia- the capital city Zagreb pilot project. Finnish Geodetic Institute Report 98:4, pp. 245-249. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Dahl, O. C., R. Forsberg: Different ways to handle topography in practical geoid determination. Phys. Chem. Earth (A), 24(1),  41-46, 1999.

Dahl, O.C., R. Forsberg: Geoid models around Sognefjord using depth data. Journal of Geodesy, 72(9), 547-556, 1998.

Daho, S.A.B., S. Kahlouche: The gravimetric geoid in Algeria: first results. In: R. Forsberg et al. (Eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 262-268, Springer, 1998.

De Santis, A., J.M. Torta: Spherical cap harmonic analysis: a comment on its proper use for local gravity field representation. Journal of Geodesy, 71(9), 526-532, 1997.

Denker, H., D. Beherend, W. Torge: The European gravimetric quasigeoid EGG95. IAG, Bulletin d' Information no 77, IGeS Bulletin no 4, pp. 3-12, 1995.

Denker, H., D. Behrend, W. Torge: A new European gravimetric geoid model (EGG95). pres. paper, XXI IUGG General Assembly, Boulder, Colorado, U.S.A., July 2-14, 1995.

Denker, H., D. Behrend, W. Torge: The European gravimetric quasigeoid. In J. Segawa et al. (Eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 532-539, Springer, 1997.

Denker, H., I.N. Tziavos: Investigation of the Molodensky series terms for terrain reduced gravity field data. Proceed. 2nd Joint Meeting of the Int. Gravity Commission and the Int. Geoid Commission, Trieste, 7-12 Sept. 1998, in print.

Denker, H., W. Torge: The European gravimetric quasigeoid EGG97 - an IAG supported continental enterprise. In: R. Forsberg et al. (Eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 249-254, Springer, 1998.

Denker, H.: Evaluation and improvement of the EGG97 quasigeoid model for Europe by GPS and levelling data. Finnish Geodetic Institute Report 98:4, pp. 53-61. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Denker, H.: Evaluation of the NASA/GSFC and NIMA joint geopotential models for Europe. IGeS Bulletin no 6, pp. 83-102, 1997.

Denker, H.: Stand und Aussichten der Geoidmodellierung in Europa. Zeitschrift f_r Vermessungswesen 121, 264-277, 1996.

Dermanis, A.: Generalized inverses of nonlinear mappings and the nonlinear geodetic datum problem. Journal of Geodesy, 72(2), 71-100, 1998.

Doerflinger, E., Z. Jiang, H. Duquenne, R. Bayer: Determination of the quasi-geoid in a mountainous area example of the Eastern Pyrenees (France). In J. Segawa et al. (Eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 643-650, Springer, 1997.

Doufexopoulou, M.G., V. N. Pagounis: Investigation of tectonic traces upon the regional geoid without the use of gravity. Finnish Geodetic Institute Report 98:4, pp. 153-159. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Doufexopoulou, M.G., R. Korakitis: On the gravimetric inverse problem in geodetic gravity field estimation. Journal of Geodesy, 71(6), 311-319, 1997.

Duquenne, H., Z. Jiang: The geoid in the Southern Alps of France. IAG, Bulletin d' Information no 77, IGeS Bulletin no 4, pp. 115-130, 1995.

Duquenne, H., M. Sarrailh: Improvement of gravimetric geoid determination in the French Alps. Finnish Geodetic Institute Report 96:2, pp. 71-76. Proceedings, Session G7, EGS XXI Gen. Assembly, The Hague, The Netherlands, 6-10 May, 1996.

Duquenne, H.: Comparison and combination of a gravimetric quasigeoid with a levelled GPS data set by statistical analysis. Phys. Chem. Earth (A), 24(1), 79-83, 1999.

Duquenne, H.: QGF98, a new solution for the quasigeoid in France. Finnish Geodetic Institute Report 98:4, pp. 251-255. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Dusatko, D., P. Koppecki, V. Vatrt: Quasigeoid of the central Europe from the multinational data. IGeS Bulletin no 6, pp. 165-166, 1997.

Eissfeller, B.: Upward continuation of Markov type anomalous gravity potential models. Journal of Geodesy, 70(9), 539-545, 1995.

Erker, E.: The geoid in Austria- one decade of application. Finnish Geodetic Institute Report 98:4, pp. 239-240. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Fan, H.: On an Earth ellipsoid best-fitted to the Earth surface. Journal of Geodesy, 72(9), 511-515, 1998.

Featherstone, W., J. Olliver: Evaluation of the DMA/GSFC geopotential models over the British isles. IGeS Bulletin no 6, pp. 131-134, 1997.

Featherstone, W.E., J.D. Evans, J.G. Olliver: A Meissl-modified Vanicek and Kleusberg kernel to reduce the truncation error in gravimetric geoid computations. Journal of Geodesy, 72(3), 154-160, 1998.

Featherstone, W.E., J.F. Kirby, K.F. Zhang, A.H.W. Kearsley, J.R. Gilliland: The quest for a new Australian gravimetric geoid. In J. Segawa et al. (Eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 581-588, Springer, 1997.

Featherstone, W.E., J.G. Olliver: A method to validate gravimetric-geoid computation software based on Stokes's integral formula. Journal of Geodesy, 71(9), 571-576, 1997.

Featherstone, W.E., M.G. Sideris: Modified kernels in spectral geoid determination - first results from Western Australia. In: R. Forsberg et al. (Eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 188-193, Springer, 1998.

Fenoglio, L., E. Groten: Mean sea level determination in small ocean basins from altimetry and tide gauge data. Manuscripta Geodaetica, 20(6), 394-407, 1995.

Font, G., M.C. Pacino, D. Blitzkow, C. Tocho: A preliminary geoid model for Argentina. In: R. Forsberg et al. (Eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 255-261, Springer, 1998.

Forsberg, R., J. Kaminskis, D. Solheim: Geoid of the Nordic and Baltic region from gravimetry and satellite altimetry. In J. Segawa et al. (Eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 540-547, Springer, 1997.

Forsberg, R., J.M. Brozena: Airborne geoid measurements in the arctic ocean. In J. Segawa et al. (Eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 139-146, Springer, 1997.

Forsberg, R., K. Hehl, L. Bastos, A. Giskehaug, U. Meyer: Development of an airborne geoid mapping system for coastal oceanography (AGMASCO). In J. Segawa et al. (Eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 163-170, Springer, 1997.

Forsberg, R.: Comparison of EGM models in the nordic region and Greenland. IGeS Bulletin no 6, pp. 115-120, 1997.

Forsberg, R.: Geoid computations in the Nordic and Baltic area. IAG, Bulletin d' Information no 77, IGeS Bulletin no 4, pp. 105-114, 1995.

Forsberg, R., W. Featherstone.: Geoid and cap. In: R. Forsberg et al. (Eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 18-23, Springer, 1998.

Forsberg, R.: Geoid tailoring to GPS - with examples of a 1-cm geoid of Denmark. Finish Geodetic Institute Report 98:4, pp. 191-197. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Forsberg, R.: The use of spectral techniques in gravity field modelling: trends and perspectives. Phys. Chem. Earth, 23(1), 31-40, 1998.

Fukuda, Y., J. Kuroda, Y. Takabatake, J. Itoh, M. Murakami: Improvement of JGEOID93 by the geoidal heights derived from GPS/levelling survey. In J. Segawa et al. (Eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 589-596, Springer, 1997.

Grafarend, E.W., A.A. Ardalan: Wo-an estimate in the Finnish height Datum N60, epoch 1993.4, from twenty five GPS points of the Baltic Sea level project. Journal of Geodesy, 71, 673-679, 1996.

Grafarend, E.W., F. Okeke: Transformation of conformal coordinates of type mercator from a global datum (WGS 84) to a Local Datum (Regional, National). Marine Geodesy, 21(3), 169-180, 1998.

Groten, E.: High precision geoid evaluation for Germany - geoid and quasigeoid. Acta Geod. Geoph. Hung. 31, 293-303, 1996.

Groten, E.: New altimetric results obtained for Baltic and Mediterranean Sea. In J. Segawa et al. (Eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 392-399, Springer, 1997.

Heck, B.: Formulation and linearization of boundary value problems: from observables to a mathematical model. In F. Sanso and R. Rummel (Eds.), Geodetic boundary value problems in view of the one centimeter geoid., Lecture Notes, pp 121-160, Springer, 1997.

Hefty, J., L. Husar, J. Melicher, M. Mojzes, J. B. Rogowski, A. Pachuta: Application of astronomical positioning for local geoid determination. Finnish Geodetic Institute Report 96:2, pp. 145-148. Proceedings, Session G7, EGS XXI Gen. Assembly, The Hague, The Netherlands, 6-10 May, 1996.

Heiland, R., B. Hofmann-Wellenhof, G. Kienast, N. Kuhtreiber: Recomputation of the Austrian astrogeodetic geoid. Finnish Geodetic Institute Report 98:4, pp. 235-238. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Higgins, M., R. Forsberg, A.H.W. Kearsley: The effects of varying cap-sizes on geoid computation - experiences with fft and ring integration. In: R. Forsberg et al. (Eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 201-206, Springer, 1998.

Hipkin, R.: Geoid models for Great Britain and the North Sea. IAG, Bulletin d' Information no 77, IGeS Bulletin no 4, pp. 131-136, 1995.

Hipkin, R.: Modelling gravity and sea surface topography in coastal areas. Proceed. XXIV EGS Gen. Assembly, The Hague, 19-23 April, 1999, in print.

Holota, P.: Geoid, Cauchy's problem and displacement. In J. Segawa et al. (Eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 368-375, Springer, 1997.

Holota, P.: Variational methods and subsidiary conditions for geoid determination. Finnish Geodetic Institute Report 98:4, pp. 99-105. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Holota, P.: Variational methods for quasigeoid determination. Finish Geodetic Institute Report 96:2, pp. 9-22. Proceedings, Session G7, EGS XXI Gen. Assembly, The Hague, The Netherlands, 6-10 May, 1996.

Holota, P.: Variational methods in geoid determination and function bases. Phys. Chem. Earth (A), 24(1), 3-14, 1999.

Hwang, C. and B. Parsons: Gravity anomalies derived from Seasat, Geosat, ERS-1 and TOPEX/POSEIDON altimetry and ship gravity: a case study over the Reykjanes Ridge. Geophys. Geophys. J. Int., 122, 551-568, 1995.

Hwang, C.: A method for computing the coefficients in the product-sum formula of associated Legendre functions. Journal of Geodesy, 70(1-2), 110-116, 1995.

Hwang, C.: Analysis of some systematic errors affecting altimeter-derived sea surface gradient with application to geoid determination over Taiwan. Journal of Geodesy, 71(2), 113-130, 1997.

Hwang, C.: Inverse Vening Meinesz formula and deflection-geoid formula: applications to the predictions of gravity and geoid over the south China Sea. Journal of Geodesy, 72(5), 304-312, 1998.

Ihde, J., U. Schirmer, F. Toppe: Geoid modelling without point masses. Finnish Geodetic Institute Report 98:4, pp. 199-204. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Ivan, M., M. J. Sevilla: Local Quasi-geoid and downward continuation by integrated harmonic series. Application to Dobrudja area-Romania. Finnish Geodetic Institute Report 98:4, pp. 128-136. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Jekeli, C.: An analysis of vertical deflections derived from high-degree spherical harmonic models. Journal of Geodesy, 73(1), 1-22, 1999.

Jekeli, C.: Spherical harmonic analysis, aliasing, and filtering. Journal of Geodesy, 70(4), 214-223, 1995.

Jiancheng, L., C. Dingbo, N. Jinsheng: Spherical cap harmonic expansion for local gravity field representation. Manuscripta Geodaetica, 20(4), 265-277, 1995.

Jiang Z., H. Duquenne: On the combined adjustment of a gravimetrically determined geoid and GPS levelling stations. Journal of Geodesy, 70(8), 505-514, 1995.

Jiang, Z., G. Balmino, H. Duquenne: On the numerical approximation of the errors in a GPS aided gravimetric geoid determination. Finnish Geodetic Institute Report 96:2, pp. 57-66. Proceedings, Session G7, EGS XXI Gen. Assembly, The Hague, The Netherlands, 6-10 May, 1996.

Jiang, Z., H. Duquenne: On fast integration in geoid determination. Journal of Geodesy, 71(2), 59-69, 1997.

Jiang, Z.: Geoid determination in France. In J. Segawa et al. (Eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 486-493, Springer, 1997.

Jiang, Z.: Geoid prediction using GPS levelling points and digital terrain model- a new French geoid determination G96-01. Finnish Geodetic Institute Report 96:2, pp. 121-128. Proceedings, Session G7, EGS XXI Gen. Assembly, The Hague, The Netherlands, 6-10 May, 1996.

Kahar, J., A. Kasenda, K. Prijatna: The Indonesian geoid model 1996. In J. Segawa et al. (Eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 613-620, Springer, 1997.

Kahlouche, S., M.I. Kariche, S.A.B. Daho: Comparison between altimetric and gravimetric geoid in the south-west Mediterranean basin. In: R. Forsberg et al. (Eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 281-287, Springer, 1998.

Kakkuri, J.: Discussion on geodetic measuring techniques to determine the sea surface topography for unification of European Vertical Datums. Finnish Geodetic Institute Report 98:4, pp. 41-46. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Kaminskis, J., R. Forsberg: A new detailed geoid for Latvia. In J. Segawa et al. (Eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 621-628, Springer, 1997.

Kaminskis, J., R. Forsberg: The geoid determination in Latvia from gravity and satellite altimetry. Finnish Geodetic Institute Report 96:2, pp. 149-156. Proceedings, Session G7, EGS XXI Gen. Assembly, The Hague, The Netherlands, 6-10 May, 1996.

Kearsley, A.H.W., R. Forsberg, A. Olesen, L. Bastos, K. Hehl, U. Meyer: Airborne gravimetry used in precise geoid computations by ring integration. Journal of Geodesy, 72(10), 600-605, 1998.

Keller, W.: Collocation in reproducing Kernel Hilbert spaces of a multiscale analysis. Phys. Chem. Earth, 23(1), 25-30, 1998.

Keller, W.: Geoid computation by collocation in scaling spaces. In: R. Forsberg et al. (Eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 176-181, Springer, 1998.

Keller, W.: On a scalar fixed altimetry-gravimetry boundary value problem. Journal of Geodesy, 70(8), 459-469, 1995.

Keller, W.: Wavelet-vaguelette decomposition as a tool in local geoid determination. Phys. Chem. Earth (A), 24(1), 15-18, 1999.

Kenyeres, A., G. Virag: Testing of recent geoid models with GPS/levelling in Hungary. Finnish Geodetic Institute Report 98:4, pp. 217-223. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Kenyeres, A.: A strategy for GPS heighting: the Hungarian solution. In J. Segawa et al. (Eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 651-658, Springer, 1997.

Kenyeres, A.: Completion of the nationwide GPS-gravimetric geoid solution for Hungary. Phys. Chem. Earth (A), 24(1), 85-90, 1999.

Kenyeres, S.: Determination and use of the geoid in Hungary. Finnish Geodetic Institute Report 96:2, pp. 81-90. Proceedings, Session G7, EGS XXI Gen. Assembly, The Hague, The Netherlands, 6-10 May, 1996.

Kirby, J.F., R. Forsberg: A comparison of techniques for the integration of satellite altimeter and surface gravity data for geoid determination. In: R. Forsberg et al. (Eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 207-212, Springer, 1998.

Kirby, J.F.: The development and application of a new algorithm for ocean geoid recovery. Ph. D. Thesis, University of Edinburgh, 1996.

Klees, R.: Boundary value problems and approximation of integral equations by finite elements. Manuscripta Geodaetica, 20(5), 345-361, 1995.

Knudsen, P., O. Andersen: Improved recovery of the global marine gravity field from the GEOSAT and the ERS-1 Geodetic Mission altimetry. In J. Segawa et al. (eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 429-436, Springer, 1997.

Korth, K., R. Dietrich, G. Reitmayr, V. Damm: Regional geoid improvement based on surface gravity data. In: R. Forsberg et al. (Eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 523-528, Springer, 1998.

Kotsakis, C., M.G. Sideris: Application of multiresolution filtering in geoid determination. In: R. Forsberg et al. (Eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 170-175, Springer, 1998.

Kotsakis, C., M.G. Sideris: On the adjustment of combined GPS/Levelling/Geoid networks. Presented at the IV Hotine-Marussi Symposium on Mathematical Geodesy, Trento, Italy, Sept. 14-17, 1998. Accepted for publication in Journal of Geodesy.

Kuhtreiber, N.: Precise geoid determination using a density variation model. Phys. Chem. Earth, 23(1), 59-64, 1998.

Kuhtreiber, N.: Using different digital terrain models for a precise Austrian geoid. In J. Segawa et al. (Eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 597-604, Springer, 1997.

Kuhtreiber, N.: Improved gravimetric geoid AGG97 of Austria. In  R. Forsberg et al. (eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 306-311, Springer, 1998.

Kumar, M., K. Burke: Realizing a global vertical datum with the use of geoid. Finnish Geodetic Institute Report 98:4, pp. 87-94. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Kusche, J., K.H. Ilk, S. Rudolph, M. Thalhammar: Application of spherical wavelets for regional gravity field recovery-a comparative study. In: R. Forsberg et al. (Eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 213-218, Springer, 1998.

Lacy de, M.C., C. Rodriguez Cadero, A.J. Jil, R. Barzaghi, F. Sanso: Quasigeoid computation in Jaen. IGeS Bulletin no 7, pp. 30-37, 1995.

Lehman, R.: Fast space-domain evaluation of geodetic surface integrals. Journal of Geodesy, 71(9), 533-540, 1997.

Lehman, R.: Information measures for global geopotential models. Journal of Geodesy, 70(6), 110-116, 1995.

Lehmann, R.: Studies on the altimetry-gravimetry problems for geoid determination. Phys. Chem. Earth (A), 24(1), 47-52, 1999.

Lelgeman, D., S. Petrovic: Bemerkungen ueber den Hoehenbegriff in der Geodaesie. Zeitschrift fuer Verm.wesen, 122, 503-509, 1997.

Li, Z., K.-P. Schwarz: Approximation of regional gravity fields from multi-scale data. In J. Segawa et al. (Eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 548-556, Springer, 1997.

Li, J., M.G. Sideris: Marine gravity and geoid determination by optimal combination of satellite altimetry and shipborne gravimetry data. Journal of Geodesy, 71(4), 209-216, 1997.

Li, J.: Detailed marine gravity field determination by combination of heterogeneous data. UCGE Report No 20102, M. Sc. Thesis, Dept. of Geomatics Eng., The Univ. of Calgary, Canada, 1996.

Li, Y.C., M.G. Sideris and K.-P. Schwarz: A numerical investigation on height anomaly prediction in mountainous areas. Bull. Geod., 69(3), 143-156, 1995.

Liu, Q.M., Y.C. Li, M.G. Sideris: Evaluation of deflections of the vertical on the sphere and the plane: a comparison of FFT techniques. Journal of Geodesy, 71(8), 461-468, 1997.

Lyszkowicz, A.: Tests of a new gravimetric geoid in GPS network. Finnish Geodetic Institute Report 96:2, pp. 77-80. Proceedings, Session G7, EGS XXI Gen. Assembly, The Hague, The Netherlands, 6-10 May, 1996.

Lyszkowicz, A.: The Polish gravimetric quasigeoid QUASI97b versus vertical reference system Kronstadt 86. Finnish Geodetic Institute Report 98:4, pp. 271-276. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Lyszkowicz, A., R. Forsberg: Gravimetric geoid for Poland area using spherical fft. IAG, Bulletin d' Information no 77, IGeS Bulletin no 4, pp. 153-162, 1995.

Lyszkowicz, A., A.A. Wahiba: The gravimetric geoid for Libya. In  R. Forsberg et al. (Eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 275-280, Springer, 1998.

Marson, I., M. Stoka, I. Velicogna, F. Coren, C. Zanolla: Gravity, geoid, isostasy and Moho depth in the Ross Sea, Antarctica. In J. Segawa et al. (Eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 351-359, Springer, 1997.

Marti, U., B. B_rki, H.-G. Kahle: National investigation in Switzerland. IAG, Bulletin d' Information no 77, IGeS Bulletin no 4, pp. 181-190 , 1995.

Marti, U.: The new geoid CHGEO97 of Switzerland. Finnish Geodetic Institute Report 98:4, pp. 281-287. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Martinec, Z., C. Matyska: On the solvability of the Stokes pseudo-boundary-value problem for geoid determination. Journal of Geodesy, 71(2), 103-112, 1997.

Martinec, Z., E.W. Grafarend: Construction of Green's function to the external Dirichlet boundary-value problem for the Laplace equation on an ellipsoid of revolution. Journal of Geodesy, 71(9), 562-570, 1997.

Martinec, Z., P. Vanicek, A. Mainville, M. Veronneau: The effect of lake water on geoidal height. Manuscripta Geodaetica, 20(3), 193-203, 1995.

Martinec, Z.: Boundary-value problems for gravimetric geoid determination of a precise geoid. Lecture notes in earth sciences, vol. 73, 223 pp., Springer, 1998.

Martinec, Z.: Construction of Green's function for the Stokes boundary-value problem with ellipsoidal corrections in the boundary condition. Journal of Geodesy, 72(7-8), 460-472, 1998.

Milbert, D.G.: Improvements of a high resolution geoid height model in the United States by GPS height on NAVD 88 benchmarks. IAG, Bulletin d' Information no 77, IGeS Bulletin no 4, pp. 13-36, 1995.

Milbert, D.G., D.A. Smith: Converting GPS height into NAVD88 elevation with the GEOID96 geoid height model. Proceedings, GIS/LIS '96 Annual Conference, Denver, 1997.

Min, Erik de: A comparison of Stokes' numerical integration and collocation, and a new combination technique. Bull. Geod., 69(4), 223-232, 1995.

Min, Erik de: The Netherlands geoid computation procedure. Finnish Geodetic Institute Report 96:2, pp. 35-40. Proceedings, Session G7, EGS XXI Gen. Assembly, The Hague, The Netherlands, 6-10 May, 1996a.

Min, Erik de: The new Netherlands geoid. Finnish Geodetic Institute Report 96:2, pp. 139-144. Proceedings, Session G7, EGS XXI Gen. Assembly, The Hague, The Netherlands, 6-10 May, 1996b.

Minchev, M., P. Gabenski: A note on the contemporary geoid investigations in Bulgaria. Finnish Geodetic Institute Report 98:4, pp. 241-244. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Mojzes, M., J. Janak: Gravimetric model of Slovak quasigeoid. Finnish Geodetic Institute Report 98:4, pp. 277-280. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Nahavandchi, H., L.E. Sjoberg: Terrain corrections to power H3 in gravimetric geoid determination. Journal of Geodesy, 72(3), 124-135, 1998a.

Nahavandchi, H., L.E. Sjoberg: Unification of vertical datums by GPS and gravimetric geoid models using modified Stokes formula. Marine Geodesy, 21(4), 261-274, 1998b.

Nahavandchi, H.: Terrain correction computations by spherical harmonics and integral formulas. Phys. Chem. Earth (A), 24(1), 73-78, 1999.

Nakane, K., Y. Kuroishi: Combined adjustment of GPS observations and geoid heights in Japan. In J. Segawa et al. (eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 637-642, Springer, 1997.

Neuman, M. Yu., J. Li, Q. Liu: Modification of Stokes and Vening-Meinesz formulas for the inner zone of arbitrary shape by minimization of upper bound truncation errors. Journal of Geodesy, 70(7), 410-418, 1995.

Nsombo, P.: Preliminary geoid over Zambia. Journal of Geodesy, 72(3), 144-153, 1998.

Olgiati, A., G. Balmino, M. Sarrailh: Gravity anomalies from satellite altimetry: comparison between computation via geoid heights and via deflections of the vertical. Bull. Geod., 69(4), 252-260, 1995.

Ollikainen, M.: GPS levelling results obtained in Finland. Finnish Geodetic Institute Report 98:4, pp. 205-210. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Pacino, M.C., G. Font, D. Blitzkow: Data processing for a geoid in Argentina. In  R. Forsberg et al. (eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 288-293, Springer, 1998.

Pagiatakis, S.D.: Towards a refined gravimetric geoid for Canada 1996-1999. IGeS Bulletin no 5, pp. 31-39, 1996.

Pan, M., L.E. Sjoberg: Unification of vertical datums by GPS and gravimetric geoid models with application to Fennoscandia. Journal of Geodesy, 72(2), 51-63, 1998.

Papp, G., J. Kalmaz, J. Juhasz: Determination and evaluation of the lithospheric geoid in the Pannonian basin, Hungary. Project report, 1998.

Paquet, P., Z. Jiang, M. Everaerts: A new Belgian geoid determination: BG96. In J. Segawa et al. (eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 605-612, Springer, 1997.

Parsons, B. A.: Strategy for the creation of a local geoidal model for the Sultanate of Oman. Finnish Geodetic Institute Report 96:2, pp. 169-174. Proceedings, Session G7, EGS XXI Gen. Assembly, The Hague, The Netherlands, 6-10 May, 1996.

Paunescu, C., C. Dina: Fitting of Romanian airport to the ETRF89 network on the WGS-84 ellipsoid. Finnish Geodetic Institute Report 98:4, pp. 211-215. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Pavlis, E. C.: On the Reference Frames Inherent in the Recent Geopotential Models. Finnish Geodetic Institute Report 98:4, pp. 29-40, 1998.

Pearse, M.B., A.H.W. Kearsley: Analysis of EGM models in New Zealand. IGeS Bulletin no 6, pp. 203-212, 1997.

Peng, M., Y. Cai Li, M.G. Sideris: First results on the computation of terrain corrections by the 3D FFT method. Manuscripta Geodaetica, 20(6), 475-488, 1995.

Perdomo, R., C. Mondinally, D. Del Cogliano: Decimetric geoid for Buenos Aires province based on GPS and global models. In  R. Forsberg et al. (eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 294-299, Springer, 1998.

Petrovic, S.: Determination of the potential of homogeneous polyhedral bodies using line integrals. Journal of Geodesy, 71(1), 44-58 , 1996.

Petrovskaya, M. S., J. B. Zielinski: Application of spatial gradiometry for constructing quasigeoid models. Finnish Geodetic Institute Report 98:4, pp. 107-112. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Poitevin, Z. Jiang, M. Everaert: Le geoide gravim_trique en B_lgique: premiers resultats. IAG, Bulletin d' Information no 77, IGeS Bulletin no 4, pp. 77-104, 1995.

Rapp, R.H.: Separation between reference surfaces of selected vertical datums. Bull. Geod., 69(1), 26-31, 1995.

Rapp, R.H.: Global models for the 1cm geoid-Present status and near term prospects. In F. Sanso and R. Rummel (eds.), Geodetic boundary value problems in view of the one centimeter geoid. Lecture Notes, pp. 273-308, Springer, 1997.

Rapp, R.H.: Comparison of altimeter-derived and shipgravity anomalies in the vicinity of the gulf of California. Marine Geodesy, 21(4), 245-260, 1998.

Reinhart, E., B. Richter, H. Wilmes, E. Erker, D. Ruess, J. Kakkuri, J. Makinen, I. Marson, J. Sledzinski: UNIGRACE - A project for the unification of gravity systems in central Europe. Finnish Geodetic Institute Report 98:4, pp. 95-98. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Rentsch, M., M. Anzenhofer, Th. Gruber, K.-H. Neumayer: Maps of altimetric gravity based on ERS-1 geodetic phase data. In J. Segawa et al. (eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 408-414, Springer, 1997.

Ritter, S.: The nullfield method for the ellipsoidal Stokes problem. Journal of Geodesy, 72(2), 101-106, 1998.

Rozsa, Sz.: Determination of terrain correction in Hungary and the surrounding area. Finnish Geodetic Institute Report 98:4, pp. 185-189. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Romaides, A.J., R.W. Sands: Elevation determination using GPS and GEOID93: Getting the topography out of gravimetry. IGeS Bulletin no 5, pp. 88-106, 1996.

Rodriguez, G., M.J. Sevilla: Geoid model in the western Mediterranean Sea. Proceed. XXIV EGS Gen. Assembly, The Hague, 19-23 April, 1999, in print.

Rummel, R., M. van Gelderen: Meissl scheme-spectral characteristics of physical geodesy. Manuscripta Geodaetica, 20(5), 379-385, 1995.

Rummel, R.: Spherical spectral properties of the earth's gravitational potential and its first and second derivatives. In F. Sanso and R. Rummel (Eds.), Geodetic boundary value problems in view of the one centimeter geoid., Lecture Notes, pp 359-401, Springer, 1997.

Sandwell, D.T., W.H.F. Smith: Marine gravity anomaly from Geosat and ERS-1 satellite altimetry. JGR, 102(B5), 10039-10054, 1997.

Sanso, F., G. Sona: The theory of optimal linear estimation for continuous fields of measurements. Manuscripta Geodaetica, 20(3), 204-230, 1995.

Sanso, F., C. Sciarretta, F. Vespe. New IGeS formulas for the terrain corrections. IGeS Bulletin no 7, pp. 68-83, 1995.

Sanso, F.: The long road from measurements to boundary value problems in physical geodesy. Manuscripta Geodaetica, 20(5), 326-344, 1995.

Sanso, F. and M.G. Sideris: On the similarities and differences between system theory and least-squares collocation in physical geodesy. Bollettino di Geodesia e Scienze Affini, 2, 174-206, 1997.

Santis, A. de , J. M. Torta: Spherical cap harmonic analysis of local gravity field. Finnish Geodetic Institute Report 96:2, pp. 67-70. Proceedings, Session G7, EGS XXI Gen. Assembly, The Hague, The Netherlands, 6-10 May, 1996.

Schrama, E.J.O.: Satellite altimetry, ocean dynamics and the marine geoid. In F. Sanso and R. Rummel (eds.), Geodetic boundary value problems in view of the one centimeter geoid., Lecture Notes, pp. 405-452, Springer, 1997.

Schwarz, K.-P., Z. Li: An introduction to airborne gravimetry and its boundary value problems. In F. Sanso and R. Rummel (Eds.), Geodetic boundary value problems in view of the one centimeter geoid. Lecture Notes, pp. 312-355, Springer, 1997.

Seeber, G., W. Torge: Eine GPS/Geoid-Hoehenuebertragung zum Meerespegel in Helgoland. Z. F. Verm.wesen, 122, 445-457, 1997.

Seeber, G., W. Torge, H. Denker, H.-J. Goldan: Praezise Hoehenbestimmung des Helgolaender Pegels. Die Kueste, 59/97, 39-61, 1997.

Sevilla, M.: A new gravimetric geoid in the Iberian Peninsula. IAG, Bulletin d' Information no 77, IGeS Bulletin no 4, pp. 163-180, 1995.

Sevilla, M.J.: A high-resolution gravimetric geoid in the Strait of Gibraltar. Journal of Geodesy, 71(7), 402-410, 1997.

Shaofeng, B., W. Xiaoping: An improved prism integration for gravimetric terrain correction. Manuscripta Geodaetica, 20(6), 515-518, 1995.

Sharni, D., H. Papo, Y. Forrai: The geoid in Israel: Haifa pilot. Finnish Geodetic Institute Report 98:4, pp. 263-270. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Sideris, M.G.: FFT geoid computations in Canada. IAG, Bulletin d' Information no 77, IGeS Bulletin no 4, pp. 37-52, 1995.

Sideris, M.G.: Fourier geoid determination with irregular data. Journal of Geodesy, 70(1-2), 2-12, 1995.

Sideris, M.G.: On the use of heterogeneous noisy data in spectral gravity field modelling methods. Journal of Geodesy, 70(8), 470-479, 1995.

Sideris, M.G., B.B. She: A new, high-resolution geoid for Canada and part of the U.S. by the 1D-FFT method. Bull. Geod., 69(2), 92-108, 1995.

Sjoberg, L. E.: The atmospheric geoid and gravity corrections. Finnish Geodetic Institute Report 98:4, pp. 161-167. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Sjoberg, L.E., H. Nahavandchi: On the indirect effect in the Stokes-Helmert method of geoid determination. Journal of Geodesy, 73(1), 87-93, 1999.

Sjoberg, L.E.: On the quasigeoid to geoid separation. Manuscripta Geodaetica, 20(3), 182-192, 1995.

Sjoberg, L.E.: The exterior Airy/Heiskanen topographic-isostatic gravity potential anomaly and the effect of analytical continuation in Stokes' formula. Journal of Geodesy, 72(11), 654-662, 1998.

Smith, D.A., D.G. Milbert: Evaluation of preliminary models of the geopotential in the united states (Addendum: Evaluation of EGM96 model of the geopotential in the United States). IGeS Bulletin no 6, pp. 7-46, 1997.

Smith, D.A., H.J. Small: The CARIB97 high-resolution geoid height model for the Caribbean Sea. Journal of geodesy, 73(1), 1-9, 1999.

Sneeuw, N., R. Sun: Global spherical harmonic computation by two-dimensional Fourier methods. Journal of Geodesy, 70(4), 224-232, 1995.

Stewart, M.P., W.E. Featherstone, J.F. Kirby, M. Dumville: Comparison of Geosat and gravimetric geoid profiles in the North Sea. Marine Geodesy, 21(4), 319-330, 1998.

Strykowski, G., O. C. Dahl: The geoid as an equipotential surface in a sense of Newton's integral - ideas and examples. Finnish Geodetic Institute Report 98:4, pp. 113-116. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Strykowski, G., R. Forsberg: Operational merging of satellite, airborne and surface gravity data by draping techniques. In  R. Forsberg et al. (eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 243-248, Springer, 1998.

Strykowski, G.: Geoid and mass density-why and how? In  R. Forsberg et al. (eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 237-242, Springer, 1998.

Strykowski, G.: Borehole data and stochastic gravimetric inversion. Dissertation, Kort & Matrikelstyrelsen, Denmark, 1996.

Sun, W., L. E. Sjoberg: A new global topographic-isostatic model. Phys. Chem. Earth (A), 24(1), 27-32, 1999.

Sun, W., L. E. Sjoberg: Gravitational potential changes of a spherically symmetric earth model caused by a surface load. Phys. Chem. Earth, 23(1), 47-52, 1998.

Sun, W., P. Vanicek: On the discrete problem on downward continuation of Helmert's gravity. Finnish Geodetic Institute Report 96:2, pp. 29-34. Proceedings, Session G7, EGS XXI Gen. Assembly, The Hague, The Netherlands, 6-10 May, 1996.

Sun, W., P. Vanicek: On some problems of the downward continuation of the 5'x5' mean Helmert gravity anomalies. Journal of Geodesy, 72(7-8), 411-420, 1998.

S_nkel, H.: GBVP-Classical solutions and implementation. In  F. Sanso and R. Rummel (eds.), Geodetic boundary value problems in view of the one centimeter geoid. Lecture Notes, pp. 219-237, Springer, 1997.

Thong, N.C.: Explicit expression and regularization of the harmonic reproducing kernels for the earth's ellipsoid. Journal of Geodesy, 70(9), 553-538, 1995.

Torge, W., H. Denker: The European Geoid-Development over more than 100 years and present status. Finish Geodetic Institute Report 98:4, pp. 47-52. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Toth, J.: Topographic-isostatic models fitted to the geopotential. Finnish Geodetic Institute Report 98:4, pp. 117-123. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Toth, J., J. Adam, Sz. Rozsa, I.N. Tziavos and V. Andritsanos: Gravimetric geoid computations in Hungary and the surrounding area. Paper presented at the 2nd joint meeting of the Int. Gravity Commission (IGC) and the Int. Geoid Commission (IGeC), Trieste, Sept. 7-12, 1998.

Tscherning, C.C., F. Rubek, R. Forsberg: Combining airborne and ground gravity using collocation. In  R. Forsberg et al. (eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 18-23, Springer, 1998.

Tsuei, G.-C., D. Arabelos, I.N. Tziavos: Recent geoid computations in Taiwan. Geomatrics Research Australasia, 65, 43-58, 1996.

Tsoulis, D.V.: A combination method for computing terrain corrections. Phys. Chem. Earth, 23(1), 53-58, 1998.

Tsoulis, D.V.: Analytical and numerical methods in gravity field modelling of ideal and real masses. Dissertation, in print, 124 pp., Munich, 1999.

Tziavos, I. N., M. G. Sideris, H. Sunkel: The effect of surface density variations on terrain modelling- A case study in Austria. Finnish Geodetic Institute Report 96:2, pp. 99-110. Proceedings, Session G7, EGS XXI Gen. Assembly, The Hague, The Netherlands, 6-10 May, 1996a.

Tziavos, I. N., M. G. Sideris, J. Li: Optimal spectral combination of satellite altimetry and marine gravity data. Finnish Geodetic Institute Report 96:2, pp. 41-56. Proceedings, Session G7, EGS XXI Gen. Assembly, The Hague, The Netherlands, 6-10 May, 1996b.

Tziavos, I. N., V. D. Andritsanos: improvements in the computation of deflections of the vertical by FFT. Phys. Chem. Earth, 23(1), 71-76, 1998.

Tziavos, I. N., V. D. Andritsanos: Recent advances in terrain correction computations. Finnish Geodetic Institute Report 98:4, pp. 169-175. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Tziavos, I. N., V. D. Andritsanos: Recent geoid computations for the Hellenic area. Phys. Chem. Earth (A), 24(1), 91-95, 1999.

Tziavos, I.N., Jinwen Li, M.G. Sideris: A comparison of marine gravity field modelling methods using non-isotropic information. In  J. Segawa et al. (eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 400-407, Springer, 1997.

Tziavos, I.N., J. Adam, Gy. Toth, V. D. Andritsanos, Sz. Rozsa: Recent geoid computations in Hungary and the surrounding area. Finish Geodetic Institute Report 98:4, pp. 257-262. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998a.

Tziavos, I.N., M.G. Sideris and R. Forsberg: Combined satellite altimetry and shipborne gravimetry data processing. Marine Geodesy, 21, 299-317, 1998b.

Tziavos, I.N., R. Forsberg, M.G. Sideris: Marine gravity field modelling using shipborne gravity and geodetic mission altimetry data. Geomatrics Research Australasia, 69, 1-18, 1998c.

Tziavos, I.N., R. Forsberg, M.G. Sideris: Marine gravity field recovery by combining satellite altimetry and shipborne gravimetry. Paper presented at the 2nd joint meeting of the Int. Gravity Commission (IGC) and the Int. Geoid Commission (IGeC), Trieste, Sept. 7-12, 1998d.

Tziavos, I.N., R. Forsberg, M.G. Sideris, V.D. Andritsanos: A comparison of satellite altimetry methods for the recovery of gravity field quantities. In  R. Forsberg et al. (eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 150-155, Springer, 1998e.

Tziavos, I.N.: Comparisons of spectral techniques for geoid computations over large regions. Journal of Geodesy, 70(6), 357-373, 1995.

Tziavos, I.N.: Evaluation of the new GSFC/DMA geopotential models in the Hellenic area and the Mediterranean Sea. IGeS Bulletin no 6, pp. 151-164, 1997.

Yu, Z.C.: A universal formula of maximum likelihood estimation of variance-covariance components. Journal of Geodesy, 70(4), 233-240, 1995.

Vajda, P., P. Vanicek: Truncated geoid and gravity inversion for one point-mass anomaly. Journal of Geodesy, 73(2), 58-66, 1999.

Vanicek, P., M. Najafi, Z. Martinec, L. Harrie, L.E. Sjoberg: Higher-degree reference field in the generalised Stokes-Helmert scheme for geoid computation. Journal of Geodesy, 70(3), 176-182, 1995.

Vanicek, P., W.E. Featherstone: Performance of three types of Stokes's kernel in the combined solution for the geoid. Journal of Geodesy, 72(12), 684-697, 1998.

Vanicek, P., W. Sun, P. Ong, Z. Martinec, M. Najafi, P. Vajda, B. Ter Horst: Downward continuation of Helmert's gravity. Journal of Geodesy, 71(1), 21-34 , 1996.

Varga, P.: Temporal variation of second degree geopotential. Finnish Geodetic Institute Report 98:4, pp. 125-128. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Verhoef, H. M. E., H. M. de Heus: Subsidence analysis from integrated GPS- and precise levelling data. Finnish Geodetic Institute Report 96:2, pp. 129-136. Proceedings, Session G7, EGS XXI Gen. Assembly, The Hague, The Netherlands, 6-10 May, 1996.

Vermeer, M.: Mass point geopotential modelling using fast spectral techniques; historical overview, toolbox description, numerical experiment. Manuscripta Geodaetica, 20(5), 362-378, 1995.

Vermeer, M.: Regularization constraints in mass point grids and their relation to gravity field stochastics. Phys. Chem. Earth, 23(1), 13-18, 1998.

Vermeer, M.: The geoid as a product. Finnish Geodetic Institute Report 98:4, pp. 63-69. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Veronneau, M.: The GSD95 geoid model for Canada. In  J. Segawa et al. (eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 573-580, Springer, 1997a.

Veronneau, M.: Evaluation of NASA/NIMA earth geopotential model (EGM96) over Canada. IGeS Bulletin no 6, pp. 47-70, 1997b.

Volgyesi, L.: Geoid computations based on torsion balance measurements. Finnish Geodetic Institute Report 98:4, pp. 145-151. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Wang Y.M.: On the error of analytical downward continuation of the earth's external gravitational potential on and inside the earth's surface. Journal of Geodesy, 71(2), 70-82, 1997.

Wang, Y.M.: On the ellipsoidal corrections to gravity anomalies computed using the inverse Stokes integral. Journal of Geodesy, 73(1), 29-34, 1999.

Wenzel, G.: Ultra high degree geopotential model GPM3E97A to degree 1800 tailored to Europe. Finnish Geodetic Institute Report 98:4, pp. 71-80. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Wildermann E., M. Hoyer, G. Acuna: Towards a regional geoid determination in western Venezuela. In R. Forsberg et al. (eds.), Geodesy on the Move. IAG Symp. Proceed. vol. 119, pp. 300-305, Springer, 1998.

Zhang, C.: A general formula and its inverse formula for gravimetric transformations by use of convolution and deconvolution techniques, Journal of Geodesy, 70(1-2), 51-64, 1995.

Zhang, C.: Estimation of dynamic ocean topography in the Gulf Stream area using Hotine formula and altimetry data. Journal of Geodesy, 72(9), 499-510, 1998.

Zhang, C., J.A.R. Blais: Comparison of methods for marine gravity determination from satellite altimetry data in Labrador Sea. Bull. Geod., 69(3), 173-180, 1995.

Zhang, K, W. Featherstone, M. Stewart, A. Dodson: A new gravimetric geoid of Australia. Finnish Geodetic Institute Report 98:4, pp. 225-233. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Zhang, K., S. Bian, W. Shen: The singular integration of physical geodesy in the frequency domain. Manuscripta Geodaetica, 20(4), 241-247, 1995.

Zhang, K.: Altimetric gravity anomalies, their assessment and combination with local gravity field. Finnish Geodetic Institute Report 98:4, pp. 137-144. Proceedings of the 2nd Continental Workshop on the Geoid in Europe, Budapest, March 10-14, 1998.

Zhang, K.: On the determination of new Australian Geoid. Phys. Chem. Earth (A), 24(1), 61-66, 1999.

Zhang, K.F., W.E. Featherstone: A preliminary evaluation of the terrain effects of gravimetric geoid determination in Australia. In J. Segawa et al. (eds.), Gravity, Geoid and Marine Geodesy IAG Symp. Proceed. vol. 117, pp. 565-572, Springer, 1997.