Appendix E

**Definitions**

**Accuracy -** The degree of conformance between the estimated or
measured position and/or velocity of a platform at a given time and its
true position or velocity. Radionavigation system accuracy is usually
presented as a statistical measure of system error and is specified as:

• Predictable - The accuracy of a radionavigation system's position
solution with respect to the charted solution. Both the position
solution and the chart must be based upon the same geodetic datum.
(Note: Appendix B discusses chart reference systems and the risks
inherent in using charts in conjunction with radionavigation systems.)

• Repeatable - The accuracy with which a user can return to a position
whose coordinates have been measured at a previous time with the same
navigation system.

• Relative - The accuracy with which a user can measure position
relative to that of another user of the same navigation system at the
same time.

**Air Traffic Control (ATC) - **A service operated by appropriate
authority to promote the safe and efficient flow of air traffic.

**Approach Reference Datum -** A point at a specified height above the
runway centerline and the threshold. The height of the MLS approach
reference datum is 15 meters (50 ft). A tolerance of plus 3 meters (10
ft) is permitted.

**Area Navigation (RNAV) -** Application of the navigation process
providing the capability to establish and maintain a flight path on any
arbitrarily chosen course that remains within the coverage area of
navigation sources being used.

**Automatic Dependent Surveillance (ADS) -** A function in which
aircraft transmit position and altitude data derived from onboard
systems via a datalink for use by air traffic control, other aircraft,
and certain airport surface vehicles.

**Availability -** The availability of a navigation system is the
percentage of time that the services of the system 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 navigation signals transmitted from
external sources are available for use. Availability is a function of
both the physical characteristics of the environment and the technical
capabilities of the transmitter facilities.

**Block II/IIA -** The satellites that form the initial GPS
constellation at FOC.

**Cellular Triangulation -** A method of location determination using
the cellular phone system where the control channel signals from a
mobile phone are captured by two or more fixed base stations and
processed according to an algorithm to determine the location of the
mobile receiver.

**Circular Error Probable (CEP) -** In a circular normal distribution
(the magnitudes of the two one-dimensional input errors are equal and
the angle of cut is 90o), circular error probable is the radius of the
circle containing 50 percent of the individual measurements being made,
or the radius of the circle inside of which there is a 50 percent
probability of being located.

**Coastal Confluence Zone (CCZ) **- Harbor entrance to 50 nautical miles
offshore or the edge of the continental shelf (100 fathom curve),
whichever is greater.

**Common-use Systems **- Systems used by both civil and military
sectors.

**Conterminous U.S. **- Forty-eight adjoining states and the District of
Columbia.

**Continuity **- The continuity of a system is the ability of the total
system (comprising all elements necessary to maintain aircraft position
within the defined airspace) to perform its function without
interruption during the intended operation. More specifically,
continuity is the probability that the specified system performance will
be maintained for the duration of a phase of operation, presuming that
the system was available at the beginning of that phase of operation.

**Coordinate Conversion - **The conversion of position coordinates from
one type to another within the same datum or geodetic reference system,
e.g., from geodetic coordinates (latitudes and longitudes) to Universal
Transverse Mercator (UTM) system (x,y).

**Coordinated Universal Time (UTC) -** UTC, an atomic time scale, is the
basis for civil time. It is occasionally adjusted by one-second
increments to ensure that the difference between the uniform time scale,
defined by atomic clocks, does not differ from the earth's rotation by
more than 0.9 seconds.

**Coverage -** The coverage provided by a radionavigation system is that
surface area or space volume in which the signals are adequate to permit
the user to determine position to a specified level of accuracy.
Coverage is influenced by system geometry, signal power levels, receiver
sensitivity, atmospheric noise conditions, and other factors which
affect signal availability.

**Datum Transformation** - The change of position coordinates from one
geodetic datum or reference system to another datum or reference system,
e.g., from European Datum 1950 to WGS 84.

**Deception (electromagnetic)** - Deliberate radiation, reradiation,
alternation, suppression, absorption, denial, enhancement, or reflection
of electromagnetic spectrum in any manner intended to convey misleading
information.

**Differential **- A technique used to improve radionavigation system
accuracy by determining positioning error at a known location and
subsequently transmitting the determined error, or corrective factors,
to users of the same radionavigation system, operating in the same area.

**Distance Root Mean Square (drms) -** The root-mean-square value of the
distances from the true location point of the position fixes in a
collection of measurements. As used in this document, 2 drms is the
radius of a circle that contains at least 95 percent of all possible
fixes that can be obtained with a system at any one place. Actually, the
percentage of fixes contained within 2 drms varies between approximately
95.5 percent and 98.2 percent, depending on the degree of ellipticity of
the error distribution.

**En Route **- A phase of navigation covering operations between a point
of departure and termination of a mission. For airborne missions the en
route phase of navigation has two subcategories, en route domestic and
en route oceanic.

**En Route Domestic **- The phase of flight between departure and
arrival terminal phases, with departure and arrival points within the
conterminous United States.

**En Route Oceanic **- The phase of flight between the departure and
arrival terminal phases, with an extended flight path over an ocean.

**Fault Detection and Exclusion (FDE) **- Fault detection and exclusion
is a receiver processing scheme that autonomously provides integrity
monitoring for the position solution, using redundant range
measurements. The FDE consists of two distinct parts: fault detection
and fault exclusion. The fault detection part detects the presence of an
unacceptably large position error for a given mode of flight. Upon the
detection, fault exclusion follows and excludes the source of the
unacceptably large position error, thereby allowing navigation to return
to normal performance without an interruption in service.

**Flight Technical Error (FTE) **- The contribution of the pilot in
using the presented information to control aircraft position.

**Free Flight -** A safe and efficient flight operating capability under
instrument flight rules in which the operators have the freedom to
select their path and speed in real time. Air traffic restrictions are
only imposed to ensure separation, to preclude exceeding airport
capacity, to prevent unauthorized flight through special use airspace,
and to ensure safety of flight. Restrictions are limited in extent and
duration to correct the identified problem.

**Full Operational Capability (FOC) - **A system dependent state which
occurs when the particular system is able to provide all of the services
for which it was designed.

**Geocentric **- Relative to the Earth as a center, measured from the
center of mass of the Earth.

**Geodesy - **The science related to the determination of the size and
shape of the Earth by such direct measurements as triangulation, GPS
positioning, leveling, and gravimetric observations.

**Geometric Dilution Of Precision (GDOP) -** All geometric factors that
degrade the accuracy of position fixes derived from
externally-referenced navigation systems.

**Global Navigation Satellite System (GNSS)** **-** The GNSS is a
world-wide position and time determination system, that includes one or
more satellite constellations, aircraft receivers, and system integrity
monitoring, augmented as necessary to support the required navigation
performance for the actual phase of operation.

**Inclination - **One of the orbital elements (parameters) that
specifies the orientation of an orbit. Inclination is the angle between
the orbital plane and a reference plane, the plane of the celestial
equator for geocentric orbits and the ecliptic for heliocentric orbits.

**Initial Operational Capability (IOC) -** A system dependent state
which occurs when the particular system is able to provide a
predetermined subset of the services for which it was designed.

**Integrity -** Integrity is the ability of a system to provide timely
warnings to users when the system should not be used for navigation.

**Interference (electromagnetic)** **-** Any electromagnetic disturbance
that interrupts, obstructs, or otherwise degrades or limits the
performance of user equipment.

**Intrusion (electromagnetic)** **-** Intentional insertion of
electromagnetic energy into transmission paths with the objective to
deceive or confuse the user.

**Jamming (electromagnetic)** **-** The deliberate radiation,
reradiation, or reflection of electromagnetic energy for the purpose of
preventing or reducing the effective use of a signal.

**Multipath -** The propagation phenomenon that results in signals
reaching the receiving antenna by two or more paths. When two or more
signals arrive simultaneously, wave interference results. The received
signal fades if the wave interference is time varying or if one of the
terminals is in motion.

**Nanosecond (ns) -** One billionth of a second.

**National Airspace System (NAS) -** The NAS includes U.S. airspace; air
navigation facilities, equipment and services; airports or landing
areas; aeronautical charts, information and service; rules, regulations
and procedures; technical information; and labor and material used to
control and/or manage flight activities in airspace under the
jurisdiction of the U.S. System components shared jointly with the
military are included.

**National Command Authority (NCA) -** The NCA is the President or the
Secretary of Defense, with the approval of the President. The term NCA
is used to signify constitutional authority to direct the Armed Forces
in their execution of military action. Both movement of troops and
execution of military action must be directed by the NCA; by law, no one
else in the chain of command has the authority to take such action.

**Nautical Mile (nm) -** A unit of distance used principally in
navigation. The International Nautical Mile is 1,852 meters long.

**Navigation -** The process of planning, recording, and controlling the
movement of a craft or vehicle from one place to another.

**Navigation System Error (NSE) - **The NSE is the error attributable to
the navigation system in use. It includes the navigation sensor error,
receiver error, and path definition error. NSE combines with Flight
Technical Error (FTE) to produce the Total System Error.

**Nonprecision Approach -** A standard instrument approach procedure in
which no electronic glide slope is provided (e.g., VOR, TACAN, Loran-C,
or NDB).

**Position Dilution of Precision -** A scalar measure representing the
contribution of the GPS satellite configuration geometry to the accuracy
in three-dimensional position.

**Precise Time -** A time requirement accurate to within 10
milliseconds.

**Precision Approach -** A standard instrument approach procedure using
a ground-based system in which an electronic glide slope is provided
(e.g., ILS).

**Primary Means Air Navigation System -** A navigation system approved
for a given operation or phase of flight that must meet accuracy and
integrity requirements, but need not meet full availability and
continuity of service requirements. Safety is achieved by limiting
flights to specific time periods and through appropriate procedural
restrictions. There is no requirement to have a sole-means navigation
system on board to support a primary-means system.

**Radiodetermination -** The determination of position, or the obtaining
of information relating to positions, by means of the propagation
properties of radio waves.

**Radiolocation -** Radiodetermination used for purposes other than
those of radionavigation.

**Radionavigation - **The determination of position, or the obtaining of
information relating to position, for the purposes of navigation by
means of the propagation properties of radio waves.

**Receiver Autonomous Integrity Monitoring (RAIM) -** A technique
whereby a GPS receiver/processor determines the integrity of the GPS
navigation signals without reference to external systems other than to
the GPS satellite signals themselves or to an independent input of
altitude information. This determination is achieved by a consistency
check among redundant pseudorange measurements.

**Reliability -** The probability of performing a specified function
without failure under given conditions for a specified period of time.

**Required Navigation Performance -** A statement of the navigation
performance accuracy necessary for operation within a defined airspace,
including the operating parameters of the navigation systems used within
that airspace.

**RHO (Ranging Mode) -** A mode of operation of a radionavigation system
in which the times for the radio signals to travel from each
transmitting station to the receiver are measured rather than their
differences (as in the hyperbolic mode).

**Roadside Beacons -** A system using infrared or radio waves to
communicate between transceivers placed at roadsides and the in-vehicle
transceivers for navigation and route guidance functions.

**Sigma -** See Standard Deviation.

**Sole Means Air Navigation System -** A sole-means navigation system
approved for a given operation or phase of flight must allow the
aircraft to meet, for that operation or phase of flight, all four
navigation system performance requirements: accuracy, integrity,
availability, and continuity of service. Note\--This definition does not
exclude the carriage of other navigation systems. Any sole-means
navigation system could include one (stand-alone installation) or
several sensors, possibly of different types (multi-sensor
installation).

**Spherical Error Probable (SEP) -** The radius of a sphere within which
there is a 50 percent probability of locating a point or being located.
SEP is the three-dimensional analogue of CEP.

**Standard Deviation (sigma) -** A measure of the dispersion of random
errors about the mean value. If a large number of measurements or
observations of the same quantity are made, the standard deviation is
the square root of the sum of the squares of deviations from the mean
value divided by the number of observations less one.

**Statute Mile -** A unit of distance on land in English-speaking
countries equal to 5,280 feet or 1,760 yards.

**Supplemental Air Navigation System -** A navigation system that may
only be used in conjunction with a primary- or sole-means navigation
system. Approval for supplemental means for a given phase of flight
requires that a primary-means navigation system for that phase of flight
must also be on board. Amongst the navigation system performance
requirements for a given operation or phase of flight, a
supplemental-means navigation system must meet the accuracy and
integrity requirements for that operation or phase of flight; there is
no requirement to meet availability and continuity requirements.
Note\--Operationally, while accuracy and integrity requirements are
being met, a supplemental-means system can be used without any
cross-check with the primary-means system. Any navigation system
approved for supplemental means could involve one (stand-alone
installation) or several sensors, possibly of different types
(multi-sensor installation).

**Surveillance -** The observation of an area or space for the purpose
of determining the position and movements of craft or vehicles in that
area or space.

**Surveying - **The act of making observations to determine the size and
shape, the absolute and/or relative position of points on, above, or
below the Earth's surface, the length and direction of a line, the
Earth's gravity field, length of the day, etc.

**Terminal -** A phase of navigation covering operations required to
initiate or terminate a planned mission or function at appropriate
facilities. For airborne missions, the terminal phase is used to
describe airspace in which approach control service or airport traffic
control service is provided.

**Terminal Area -** A general term used to describe airspace in which
approach control service or airport traffic control service is provided.

**Theta -** Bearing or direction to a fixed point to define a line of
position.

**Time Interval -** The duration of a segment of time without reference
to where the time interval begins or ends.

**TOPEX/POSEIDON -** TOPographic EXperiment/POSEIDON mission, a joint
U.S./French oceanic mapping mission launched in August 1992.

**Total System Error (TSE) -** The TSE comprises both the aircraft and
its navigation system tracking errors. It is the difference between true
position and desired position. This error is equal to the vector sum of
the path steering error, path definition error, and position estimation
error.

**Universal Transverse Mercator (UTM) Grid -** A rectangular grid of
east-west and north-south lines, with linear scale of 0.9996 along the
central meridian, and based on the Transverse Mercator projection;
mostly used on military maps and charts from 84oN and 80^o^S latitudes.

**Vehicle Location Monitoring -** A service provided to maintain the
orderly and safe movement of platforms or vehicles. It encompasses the
systematic observation of airspace, surface and subsurface areas by
electronic, visual or other means to locate, identify, and control the
movement of platforms or vehicles.

**World Geodetic System (WGS) -** A consistent set of constants and
parameters describing the Earth's geometric and physical size and shape,
gravity potential and field, and theoretical normal gravity.