Results of Recent Experiments with Differential OMEGA

Abstract

Evaluation tests of the DIFFERENTIAL OMEGA mode of electronic navigation associated with an original procedure for transmission and application of skywave corrections (SWC) by automatic means have recently been conducted at land-based locations and on board ships at sea. The procedure under review, which is capable of an accuracy better than 1 centicycle (CEC) in the transmission of SWCs by a single station is quite simple and cheap up to a distance of 400 n.m. The system has been designed to permit up to eight such transmitters being included in one frequency range (total bandwidth 1.2. Khz). With the chain of transmitters thus constituted up to 5,000 km of ocean coast may be covered at little cost. Tests have been carried out using a SWC transmitter with a coverage of 400 n.m. and a mobile receiver unit comprised of a conventional OMEGA receiver, a differential OMEGA receiver, and a TORAN radiolocation receiver with a position location capability better than 50 meters for calibration purposes. All these were digitized instruments and their outputs were, in addition, simultaneously recorded on paper tape (analog presentation) and punched tape (teleprinter ASR 33). A comprehensive program was used to translate the data thus collected to geographical coordinates, and to compute errors in terms of OMEGA phase discrepancies, and also in terms of distance and azimuth with respect to the reference position given by TORAN readings. Recordings have been made ashore over distances of from 5 to 300 km, in addition to two experimental campaigns at sea. A total of over 10,000 measurement points have been logged over a 3 deg × 3 deg area having its center at 46 N × 3 W. Results have fully substantiated what was expected of the system in its present configuration.