Rapid growth of geodetic information provided by the Global Positioning System (GPS) and stringent requirements for a precise geoid in ocean areas for ocean circulation models have spurred interest in geoid studies. As a result, the International Geoid Commission was formed to provide a focus for this important geoid research. Determination of the Geoid : Present and Future is the result of the first meeting of the Commission, held at the Instituto di Topografia, Fotogrammetria e Geofisica at the Politecnico di Milano, June 1990. Six major topics are presented: Global Geopotential Models: Present and Future; Role of Topography in Geoid Computations; the Geoid and the Global Positioning System; the State of Computation of National or Regional Geoids; Software and Data Improvements for Geoid Computations; and Recent Developments in the GEOMED (Determination of the Geoid in the Mediterranean) Project.

Zusammenfassung
Symposium No. 106, Milan, Italy, June 11-13, 1990

Inhalt
Welcome Address.- Global Geopotential Models: Present and Future.- OSU89A/B Potential Coefficient Models.- The Aliasing Effect in Coefficients Estimation.- Grim-4: A New Global Earth Gravity Model (Status Report).- Geoid Recovery at 0.5 Degree Resolution from Global Satellite Gradiometry Data Sets.- Compact Approximation of the Geoid Height on the Base of Modified High Resolution Global Geopotential Models.- An Improved Method to the Earth's Potential Coefficients Estimation.- The Role of Topography in Geoid Computations: The Marine Geoid.- Review of Geoid Prediction Methods in Mountainous Regions.- Estimation of the Gravity Field and Sea Surface Heights from Heterogeneous Data in the Central Mediterranean.- Altimetry Based Geoid Determination at the German Processing and Archiving Facility Within the ERS-1 Project.- The Determination of Oceanic Geoid Using Modified Hotine Integral.- A Strategy for Gross-Error Detection in Satellite Altimeter Data Applied in the Baltic-Sea Area for Enhanced Geoid and Gravity Determination.- Altimetry Rank Deficiency in Crossover Adjustment.- Practical Considerations in the Use of FFT Methods for Computing Terrain Effects.- Regularization by Digital Topography and by Estimating Crustal Parameters from Gravity Field Data: Example of Switzerland.- The Geoid and GPS.- Estimation of the Disturbing Potential Components and Comparison with GPS and Astrogeodetic Data.- GPS Control of the 1989 Gravimetric Quasigeoid for the Federal Republic of Germany.- Orthometric Heights Using GPS in Canada.- Determination of the Regional Geoid from Simulated GPS Measurements by the Aristoteles Solid-Earth Satellite.- Gravimetric and Astrogeodetic Measurements at GPS Locations in Karakorum.- GPS and Spirit Leveling Measurements in NE Italy.- State ofComputation of National or Regional Geoids.- Comparison of Geopotential Models in the Region of Hungary.- Test Computations for a Local Quasigeoid in Hungary Using FFT.- Derivation of the Most Reliable Geoid in the Area of Japan and Some Comments on the Variability of Sea Surface Topography.- ITALGEO '90: Progress Report June '90.- New Gravimetric Geoid for Canada: the UNB '90 Solution.- The Swiss Geoid Computation: A Status Report.- Estimation Models of Geoid in Nigeria Using Doppler Satellite Observations.- A New High-Resolution Geoid of the Nordic Area.- Geoid Evaluation in Australia: Status and Problems.- Free-Air Gravity Anomalies in Kenya.- Efforts Towards a Preliminary Gravimetric Geoid Computations in Poland Area.- The Gravimetric Geoid in Spain: First Results.- Finland: National Report.- Possible Improvements of the Existing European Geoid.- Theoretical Improvements in the Determination of the Geoid.- Nonspherical Boundary Value Problem by Pseudodifferential Operators.- A Global Geoid Computation by a Solution of the Bipotential Equation.- The Geoid and Its Computation from the Gravimetric Boundary Value Problem.- Some Integral Formulas for a Non-Spherical Earth.- Coerciveness and Geometry in the Linear Gravimetric Boundary Value Problem: Reduced Version.- Holes in Boundary and Out-of-Boundary Data.- The Boundary Equation Approach to the Geoid.- The Geoid, Green's Functions and the Gravimetric Boundary Value Problem for the Spheroid Earth.- Correlation of Strain Representations of the Potential Anomalies with the Geoid.- On the Joint Use of Seismic and Gradiometric Data in Identifying Density Anomalies.- Software and Data Improvement for Geoid Computations.- A New Direct Solution of the Transformation Problem of Cartesian into EllipsoidalCoordinates.- Stokes Formula Using Fast Fourier Techniques.- Simulation of Regional Gravity Field Recovery from Satellite Gravity Gradiometer Data Using Collocation and FFT.- The GEMT1 Variance-Covariance Matrix: Its Characteristics and Applications in Geoid Computations.- Some Accuracy Estimates of Local Geoids.- Numerical Behaviour of Covariance Matrices and Their Influence on Iterative Solution Techniques.- Fast Collocation.- Poster Session.- GEOMED: An International Project for the Determination of the Geoid in the Mediterranean.- Preprocessing of Altimetric and Gravimetric Data in the Mediterranean Area.- Data Collection, Data Validation and Statistics of Geophysically Relevant Data.- GEOMED: Gravimetry Data Validation: Status Report.- Analysis of GEOSAT Altimeter Data.- Use of Point Masses on Optimized Positions for the Approximation of the Gravity Field.- List of Participants.- Author Index.