With the increasing application of the Navy Navigation Satellite System (NNSS) to both land surveying and offshore drill rig and platform positioning, a need has arisen for a comparison of the performance and cost of standard satellite positioning techniques versus translocation positioning techniques using satellites. Translocation positioning is a technique by which two satellite receivers are used at separate sites to quickly establish one of the site's position when the other site's position is well known. This paper provides data to help the NNSS user decide which technique is best suited for his application.
Data is presented from two tests performed in Southern California which made use of both dual channel and single channel satellite receivers. Conclusions are drawn from these results as to the accuracies and cost effectiveness of the two positioning techniques. In particular, cost effective trade offs between single and dual channel satellite receivers are presented for possible applications such as drill rig or platform positioning, benchmark studies, land survey studies and monument placing.
For the past three years, the Navy Navigation Satellite System (NNSS) has been used extensively as a navigation and positioning source for the commercial offshore industry. A need has arisen for data comparing different positioning techniques and their respective accuracies and costs. This paper describes two tests whose results provide the user with information leading to this end. Specifically, data will be presented comparing accuracies and costs of standard satellite positioning and translocation positioning.
A brief description of the NNSS will be presented along with a description of the test equipment and test procedure. From results of the data taken on this equipment on days 263 through 269 of calendar year 1971 several conclusions on accuracy and cost will be drawn.
Previously published literature contains several excellent reports describing the NNSS (References 1 and 2), hence the description given here will be brief.
The NNSS is a world-wide, all weather system from which accurate position fixes can be obtained using the data transmitted from five orbiting satellites which are supported by four tracking stations, two injection stations, the U. S. Naval Observatory, and a computing center. Since the user is passive, any number of navigational installations can exist with no interference between them.
The navigation satellites are placed in circular, polar orbits about earth at an altitude of approximately 600 nautical miles. The orbital planes of the satellites have a common point along the earth's rotational axis. Each satellite orbits the earth approximately every 107 minutes. The geometrical placement of the orbiting satellite allows an earth bound observer to cross directly under each satellite orbit twice daily. Typically, the observer receives data from the satellite twice each time he is near an orbit because the satellites appear to traverse longitudinally as the earth rotates. The earth rotates 27 degrees longitudinally per satellite pass. At the equator, about 20 fixes daily are possible. Realistically, about 12 good quality fixes daily can be realized.
