Appendix 3 Par 1 1 APPENDIX 3. GLOSSARY
1. Availability. The availability of the overall system or a particular sensor is the percentage of time that the services of the system/sensor are usable. Availability is an indication of the ability of the system to provide usable service within the specified coverage area. Signal availability is the percentage of time that navigational signals transmitted from the satellites or ground stations are available for use.
2. Area Calibration. Area calibration is a procedure where time measurement correction factors are input into the Loran-C system to reduce the effect of propagation anomalies.
3. Barometric altitude. Altitude in the earth’s atmosphere above mean standard sea level pressure datum plane, measured by a pressure (barometric) altimeter and corrected for local barometric pressure setting.
4. Differential GPS. A technique used to improve GPS system accuracy by determining positioning error from the GPS satellites at a known fixed location and subsequently transmitting the determined error, or corrective factors, to GPS users operating in the same area.
5. Distance Root Mean Square (DRMS). The root-mean-square value of the distances between the measured and true location in a collection of measurements. The two dimensional circular error distribution, where 95 percent of the position solutions must lie within the defined radius of the circle, is represented by two times the DRMS (2DRMS).
6. En Route Operations. The phase of navigation covering operations between departure and termination phases. The en route phase of navigation has two subcategories: en route domestic and en route oceanic/remote.
7. En Route Domestic. The phase of flight between departure and arrival terminal phases, with departure and arrival points within the U.S. National Airspace System (NAS).
8. En Route Oceanic and Remote. The phase of flight between the departure and arrival terminal phases, with an extended flight path over an ocean.
9. Flight Technical Error (FTE). Navigation error introduced by the pilot’s (or autopilot’s) capability to utilize displayed guidance information to track the desired flight path.
10. Geometric Dilution of Precision (GDOP). A measure of the satellite geometric effects that degrade a user’s position determination.
11. GPS Equipment Classes A(), B(), and C(). GPS equipment is categorized into the following classes (ref. TSO-C129):
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a. Class A(). Equipment incorporating both the GPS sensor and navigation capability. This equipment incorporates Receiver Autonomous Integrity Monitoring (RAIM).
Class A1 equipment includes en route, terminal, and non-precision approach navigation capability. Class A2 equipment includes en route and terminal navigation capability only.
b. Class B(). Equipment consisting of a GPS sensor that provides data to an integrated navigation system (i.e., flight management system, multi-sensor navigation system, etc.). Class B1 equipment includes RAIM and provides en route, terminal, and non-precision approach capability. Class B2 equipment includes RAIM and provides en route and terminal capability only. Class B3 equipment requires the integrated navigation system to provide a level of GPS integrity equivalent to RAIM and provides en route, terminal, and non-precision approach capability. Class B4 equipment requires the integrated navigation system to provide a level of GPS integrity equivalent to RAIM and provides en route and terminal capability only.
c. Class C(). Equipment consisting of a GPS sensor that provides data to an integrated navigation system (i.e., flight management system, multi-sensor navigation system, etc.), which provides enhanced guidance to an autopilot or flight director in order to reduce flight technical error. Installation of Class C() equipment is limited to aircraft approved under 14 CFR part 121 or equivalent criteria. Class C1 equipment includes RAIM and provides en route, terminal, and non-precision approach capability. Class C2 equipment includes RAIM and provides en route and terminal capability only. Class C3 equipment needs the integrated navigation system to provide a level of GPS integrity equivalent to RAIM and provides en route, terminal, and non-precision approach capability. Class C4 equipment requires the integrated navigation system to provide a level of GPS integrity equivalent to RAIM and provides en route and terminal capability only.
12. Horizontal Dilution of Precision (HDOP). The satellite geometric effects which perturb a user’s horizontal error (east and north). Combination of east dilution of precision and north dilution of precision.
13. Integrity. The probability that the system will provide accurate navigation as specified or timely warnings to users when navigation data from a particular sensor should not be used for navigation.
14. Mask Angle. A fixed elevation angle referenced to the user’s horizon below which GPS satellites are ignored by the receiver software. The mask angle is driven by the receiver antenna characteristics, the strength of the transmitted signal at low elevations, receiver sensitivity and acceptable low elevation errors.
15. Non-Precision Approach Operations. Those flight phases conducted on charted nonprecision Instrument Approach Procedures (IAP’s) commencing at the initial approach fix and concluding at the missed approach point or the missed approach holding fix, as appropriate.
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16. Operating Modes. Multi-sensor equipment modes associated with various phases of flight: i.e., oceanic, en route, terminal, and non-precision approach.
17. Precipitation Static (P-Static). P-static is electromagnetic noise generated by the dissipation of an electrical charge from an aircraft into the atmosphere. The aircraft becomes charged by flight through particles suspended in the atmosphere such as dust, ice, rain, or snow.
Unprotected aircraft may create so much noise that the Loran-C or Omega/VLF sensor can no longer detect the transmitted signal.
18. Pressure Altitude. Altitude in the earth’s atmosphere above mean standard sea level pressure datum plane, measured by a pressure (barometric) altimeter set to standard pressure
(29.92 inches of mercury).
19. Receiver Autonomous Integrity Monitoring (RAIM). A technique whereby a civil GPS receiver/processor determines the integrity of the GPS navigation signals using only GPS signals or GPS signals augmented with altitude. This determination is achieved by a consistency check among redundant measurements. At least one satellite in addition to those required for navigation must be in view for the receiver to perform the RAIM function.
20. Stand-Alone Navigation System. Stand-alone equipment is equipment that is not combined with other navigation sensors or navigation systems. Stand-alone GPS equipment can, however, include other augmentation features such as altimeter smoothing, clock coasting, etc.
21. Standard Positioning Service (SPS). The standard specified level of positioning, velocity and timing accuracy that is available, without qualifications or restrictions, to any user of the GPS system on a continuous worldwide basis. The navigation service associated with SPS is specified to be 100 meters 2 DRMS horizontal error. 2 DRMS is defined to represent 95 percent.
22. Supplemental Air Navigation System. An FAA-approved navigation system that can be used for navigation provided an alternate navigation system, which meets all of the regulatory requirements for the route of flight, is also installed on the aircraft.
23. Terminal Area Operations. Those flight phases conducted on charted Standard Instrument Departures (SID’s), on Standard Terminal Arrivals (STAR’s), or other flight operations between the last en route fix/waypoint and an initial approach fix/waypoint.
24. Time Difference (TD). The elapsed time, in microseconds, measured at the receiver, between the arrival of a set of pulses from one Loran-C station’s signal to the arrival of a set of pulses from another Loran-C stations signal.
25. Track Angle Error. Track angle error is the difference between the desired track and actual track (magnetic or true).
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26. Triad. The collective name given to the three stations from a Loran-C chain from which navigational information is being derived.