The Realities Of Radio Positioning

ABSTRACT The field of radio positioning has grown from the simple rotatable antenna and AM receiver of the direction finder to a wide assortment of complex electronic systems with a correspondingly broad variety of performance and operational characteristics. The intelligent use of any specific radio positioning system must, therefore, 'require a reasonable understanding not only of its performance capabilities under jdea1 conditions, but also the constraints that determine its true effectiveness in the environment of actual operation. The cost and quality (cost effectiveness) of the positioning end product in the geophysical industry is a direct function of the quality of the numerous interfaces which should exist between the ultimate user and the service organizations providing the geophysical and positioning data. A review of available generic radio positioning systems serves to indicate the need for intelligent system selection and operation. A first order analysis of the interfaces which can exist throughout a routine geophysical mission points out numerous opportunities to improve the end product cost effectiveness by adequate mission definitions, thoughtful mission planning, and operational communications and control. Based upon a general appreciation for the operational mission problems, some specific areas are identified where timely attention and communications are most likely to reap positive benefits for all those associated with the survey. Finally, current trends indicate that radio positioning systems will provide increasingly satisfactory survey data over at least the near future. 1.0 INTRODUCTION Survey control for the vast majority of marine geophysical data collection missions is currently provided by a class of navigation systems which can be generically defined as radio positioning. While the low frequency end of these systems (10.2 KHZ) overlaps into the acoustical range and the high end (laser) reaches the visual, all share the common characteristic of producing positioning information based on measurement of electromagnetic signal propagation above the earth's surface, and wholly within the earth's atmospheric envelope. With radio positioning systems operating across such a wide frequency spectrum (distributed into discrete bands by international and national priorities) It Is obvious that even ideal performance characteristics will be quite diverse. In fact, the only generalization of ideal performance ‘the higher the frequency, the greater the accuracy’ can be a tenuous notion in the presence of the operating environment. Since radio positioning systems play such an important role in marine geophysical activities, a reasonable appreciation of their performance under operational conditions can lead to the production of an improved quality survey end product at reduced cost. Thus, the cost effectiveness of the overall geophysical mission can be significantly affected by the levels of understanding and attention afforded the positioning subsystem in the total mission system.