The transit system, 1977: performance, plans and potential

Abstract

The precision of the Transit System is described since the introduction of the software improvements in 1975. The surveyor’s rather than the navigator's use of Transit is emphasized. The differences between the basic elements of (1) the classical surveying technique, and (2) the Doppler technique are contrasted. It is necessary to consider the geopotential model as part of the Doppler datum definition. Geopotential model changes create positional shifts which vary from point to point. Datum transformations on a global scale, then, are much more complicated than the recent literature indicates. Current techniques for minimizing correlated errors, principally drag, are discussed, as are immediate extensions to sub-metre precision. A major software change in the Transit orbit generation computation is planned for late 1979. A new satellite is currently in limited production. Implications for users of the system are described.