AN/BRN-7 Computer Program Specification. Volume VII. Propagation Prediction Subprogram Design.
Abstract
In order for a submarine to successfully determine its current position from the phase information received, it must know the phase velocity of the incoming wave along the path, and the path length. To obtain a more accurate estimate of submarine position, one must consider a number of effects (magnetic, day/night (diurnal), ground conductivity, and variations in radius of the earth) that cause position to deviate from that calculated using constant velocity over an assumed perfect sphere. The OMEGA Navigation System is based on measurement of the phase of several transmitters operating in the 10-14 kHz electromagnetic spectrum. It has been established that the 8 proposed OMEGA transmitters will cover the earth with signal levels adequate to permit that phase measurement. It is also accepted that signals in this spectrum propagate through a waveguide made up of two concentric spheres--one sphere the earth, the other the ionosphere. Under ideal conditions a simple phase measurement would suffice to locate a receiving station precisely. However, the walls of the waveguide are not perfect and are affected by several parameters, specifically the effect of the sun on the ionosphere; earth's magnetic field; ground conductivity, and others. These imperfections in the waveguide walls cause changes in the propagation of the electromagnetic signal, the phase velocity, which reduce the accuracy of the phase measurement.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 12, 1973
- Accession Number
- ADA047912