An attempt is made to summarize arguments for defining geodetic coordinates in the four-dimensional sense, in a manner that will permit their use without undue complexity over extended periods of time for geophysical and geodynamic purposes. Such arguments cannot be isolated from the consideration of techniques for position determination with the highest possible precision for other purposes that are potentially beneficial for the global community, in view of the capital expense involved. The types of observations that offer the most promise in the achievement of these goals are also a factor in the development. A simple system of reference that fulfills the basic requirements of geodetic determinations of this type is described in the context of inter-relations between the geometric and dynamic characteristics of the earth. System requirements for the implementation of such a scheme are outlined. There is disagreement on whether geodesy can contribute any data of significance in the short term, apart from that for studies of gross effects in local regions, toward understanding earthquake mechanisms. However, the overall cost-benefit-oriented geodetic requirements, calling for determinations of the highest precision, appear to warrant the maintenance of a worldwide geodetic network and associated measuring systems in a manner that would also permit the determination of those time variations in geodetic coordinates with global relevance. A historical perspective makes it mandatory that such a scheme be initiated in the next decade, in view of the favorable portents for a significant improvement in the measuring precision.
Determination of the 30-year creep trend on the Ismetpaşa segment of the North Anatolian Fault using an old geodetic network