MIAS, the Integration of MLS with DGPS/DLoran-C

Durk van Willigen and Elso P. M. Vlietstra

Abstract:	The proposed MLS-Integrated Approach System (MIAS) is a proposed hybridization of the Microwave Landing System with DGPS and DLoran-C. MIAS yields full 3-dimensional guidance during the approach phase of the flight, and additionally gives improved GPS and Loran-C integrity (RAIM). In the coming decades VOR/DME will be phased out as en-route navigation aid ill. This implies that from then on airborne DME equipment is needed in the approach phase only. A cost impairing fact, especially to the general aviator. However, with non- precision approaches, use of MIAS makes the on-board DME/P equipment obsolete. The already available GPS and Loran-C en-route ‘navigators’ can smoothly take over this DME/P task during such approaches, thereby reducing power, weight and cost. For precision- (CAT II/III) and also for compu- ted center line approaches, MIAS does in the DME-less mode and without GPS not fully meet the standard MLS specifications. However, GPS and Loran-C remain powerful additional navigational landing aids offer- ing increased integrity during precision approaches. MIAS applies GPS and Loran-C in the differ- ential mode. The yet unassigned MLS auxil- iary data words thereto transfer DGPS, DLoran-C and integrity data from the refer- ence station to the aircraft. The per- formance of this MLS data channel complies with the RTCM-104 SC requirements. The integration of DGPS with MLS offers a performance which exceeds the standard MLS specs for the window size at the threshold. The Along Track Error (ATE) is reduced from 30 meters (ti-DME/Pl to the lateral DGPS error which is less than 10 meters (-1. Further, the cooperation of two fully independent localization devices improves realibility, availability and integrity. MIAS offers in the general aviation mode, where it is based on MLS angles in conjunction with DLoran-C, at the decision height of 200 ft (CAT I with a 3 degrees GS), height-, X-track- and along-track errors of less than 5, 2 and 90 meters (95%), respectively. Whenever DGPS is available, the height- and the along-track errors further reduce to less than 2 and 10 meters, respectively.
Published in:	Proceedings of the 1992 National Technical Meeting of The Institute of Navigation January 27 - 29, 1992 Catamaran Resort Hotel San Diego, CA
Pages:	47 - 55
Cite this article:	van Willigen, Durk, Vlietstra, Elso P. M., "MIAS, the Integration of MLS with DGPS/DLoran-C," Proceedings of the 1992 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 1992, pp. 47-55.
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