ABSTRACT

The Transit Navigation Satellite System has been used principally for obtaining discrete position fixes while underway. Also, in most installations the satellite equipment has operated independently of other shipboard navigation sensors. This paper describes two new applications of the Transit System.

First is a unique fixed site survey technique, applicable to positioning of land stations or of offshore drill rigs. The technique employs the raw data gathered from several satellite passes to obtain a single, three-dimensional (latitude, longitude, height) position fix to an accuracy of 10 meters. As contrasted with conventional satellite techniques, this new approach requires fewer satellite passes (less time) to achieve a given level of accuracy, permits use of more of the available satellite passes, and eliminates the requirement for accurate knowledge of height above the reference datum. An extension of this technique, called three-dimensional translocation, permits determining relative positions to an accuracy of 5 meters over 100-200 mile ranges.

Second is a description of the Magnavox Model 100 Integrated Navigation System, which is now operating out of Singapore. The system combines outputs from a doppler sonar and a gyrocompass to provide continuous navigation, automatically updated by each satellite fix to an accuracy of 200. feet or better. The system initiates firing of seismic shots, and logs time, position, gravity reading, and magnetometer output at each shot point on IBM compatible magnetic tape. These and other system functions have been implemented in the 8,192 word computer normally provided for satellite navigation alone, thus avoiding the considerable expense of a larger machine. This paper emphasizes human factors of how the system is used and what performance has been obtained.

INTRODUCTION

The Model 100 Integrated Navigation System is covered in later sections of this paper; the first sections are devoted to fixed site survey by satellite.

New features and improvements have been added regularly to the computer programs available for use with the Magnavox satellite navigation equipment, the MX/702;hp, pictured in Figure 1. Particularly noteworthy have been:

  1. MAPS-69227, the first short doppler (24 second) satellite navigation program issued to all MX/702!hp users in August, 1969. (See Reference 1.)

  2. MAPS-70065, improved accuracy short doppler program issued in March, 1970.

  3. Built-in alert capability, allowing the navigation program also to compute alerts for any satellite, available in late 1970.

  4. Continuous dead reckoning capability, available in late 1970.

  5. Velocity north solution (4 × 4 program) available in early 1971.

  6. MAPS-N-70356, improved short doppler position fix program issued in February, 1971.

None of these improvements has required modification of the receiver equipment nor expansion of the computer.

All of the preceding list of programs have been directed primarily toward fulfilling shipboard requirements for accurate position fixes while underway. Many times, however, the equipment has been used to obtain the position of a fixed site, such as an offshore drill rig.

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