The MOPS specifies availability which satisfies false alert probability and missed alert probability as well. To verify this, it is necessary to perform simulation on the relation of position vs time, using 24 GPS satellites and 3 SBAS satellites over 12 hours in increment of 5 min (144 data) at 2,353 points (338,832 points-time in total) in Northern Hemisphere. [1] (2.5.9.2 Availability Test, Appendix B) The results obtained from the simulation using our Receiver are shown below:

Firstly, the results of availability simulations for failure detection and exclusion of failed satellite where integrity is guaranteed by FD/FDE are shown in Table 5 and 6 depending on SA presence/absence and navigation modes.

　

Table 5.　Results of availability simulation for FD

Table 6.　Results of availability simulation for FDE

　

Secondly, the results of availability simulations for failure detection at the time of precision approach mode where integrity is guaranteed by WAAS are shown in Table 7.

　

Table 7.　Results of availability simulation for FD on PA

　

8.　CONCLUSION

　

We have successfully completed the development of the prototype GPS/WAAS Receiver. This proves that the MOPS is effective technical standard in development of GPS/WAAS receiver from both viewpoints of software and hardware.

We are currently performing the verification work using a simulator. In parallel, we are evaluating receiving performance using actual satellites in orbit. Unfortunately, the only satellite that is available in Japan is POR as mentioned in clause 6 and thus the ionospheric correction cannot be used at all. Further to say, the number of satellites that can feed the fast and long-term correction is roughly a half of those which are in view in Japan. Under the circumstances and in order to overcome these short-comings, we have the plan for the future receiving experiments:

　

1)　Position-fixing experiments using the correction provided by ENRI;

2)　Position-fixing experiments using POR and AOR-W in thc United States;

3)　Position-fixing experiments using MTSAT.

　

ACKNOWLEDGEMENTS

　

The Authors would like to thank Nippon Foundation, Japan Civil Aviation Promotion Foundation, Japan Civil Aviation Bureau and ENRI, for the support of development of our prototype GPS/WAAS Receiver.

　

REFERENCE

　

[1]　Minimum Operational Performance Standards for Global Positioning System/Wide Area Augmentation System Airborne Equipment, RTCA/DO-229A,RTCA Inc., 1998/06

　

[2]　Lee,Y.C., “Example Fault Detection and Exclusion Algorithm”, RTCA Paper No.595-95/SC-159-683

　

[3]　Pakinson,B.W. and Axelrad,P.A., ”Autonomous GPS Integrity Monitoring Using the Pseudorange Residual,”NAVIGATION, Journal of The Institute of Navigation, Vol.35,No.2, Summer 1988,pp.255-74

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