AvMap GeoPilot II Plus - Manual (Page 84)

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used. Ranges from 00 (lowest) to 99 (highest). A scale for indicating the strength of the signal and
the likelihood of the lock on the signal being lost.
TCA - TERMINAL CONTROL AREA - Class B airspace.
TPA - TRAFFIC PATTERN ALTITUDE - The Altitude required when entering the traffic pattern.
TrACK - The historical movement over the ground.
TrACKS & roUTeS - Recommended and established routes for ships at sea, including traffic
separation schemes, deep water routes.
TrUe norTh - Geographic north, located at the earth’s north pole.
TTG - TIME TO GO - The estimated time needed to reach your destination, based on your current
speed and the distance to destination.
TWr - TOWER FREQUENCY - The radio frequency for contacting the tower.
UnICom - UNICOM FREQUENCY - Used for general traffic advisories. Provides airport information
for non controlled airports.
UTC - UNIVERSAL TIME - The current time at the Prime Meridian. Abbreviated as UT or UTC. Also
ref. to as Zulu time (Z)
USer ComPACT flASh - The Geopilot II Plus uses the optional User COMPACT FLASH to save
user data: it is a convenient medium to store and retrieve your information.
USer WAYPoInT - Place on the chart identified by its coordinates and displayed on the screen
with a reference symbol .
UTm - Universal Transverse Mercator - Metric Grid system used on most large and intermediate
scale land topographic charts and maps.
vdoP - (Vertical Dilution Of Precision)
vnAv - Vertical Navigation - The actual path of the aircraft descending to a final destination.
Provides descent point, Altitude and rate information.
vorTAC - A navaid that provides a VOR, DME and TACAN at one site.
WAAS - Wide Area Augmentation System - The Federal Aviation Administration (FAA), in
cooperation with other DOT organizations and DOD, is augmenting the GPS/SPS with a
satellite-based augmentation system, the WAAS. It will provide a signal-in-space to WAAS users
to support en route through precision approach navigation. After achieving initial operational
capability, the WAAS will then be incrementally improved over the next years to expand the area
of coverage, increase the availability of precision approaches, increase signal redundancy and
reduce operational restrictions.
WAYPoInT - Any point to which one intends to navigate. A sequence of Waypoints makes up a
Flight Plan.
WGS84 - World Geodetic System 1984 Coordinates System or Datum developed by the Defense
Mapping Agency (DMA).
xTe - Cross Track Error - The perpendicular distance between the present position and the course
line. Given as a distance right or left of course when facing the destination. Displayed in NAV as
XTE or on the CDI as a deflection.
‘+’ - Shows more detail in a smaller area.
‘-’ - Shows a wider area with less details.
APPendIx b - mAP dATUm
A map datum is a mathematical description of the earth or a part of the earth and is based on the
ellipsoid or the arc of an ellipsoid that most closely represents the area being described. In addition,
the datum is centered at a specific location (the datum origin). A datum may describe a small
part of the earth, such as California or Iceland or may describe the entire earth, such as WGS84,
depending on which ellipsoid or ellipsoidal arc is selected.
Since datums use different ellipsoids and origins, the LAT/LON coordinates of the same position
differs from one datum to another. The difference may be slight or great, depending on the datums
involved, but will affect the apparent accuracy of the positioning information provided by a GPS
receiver. GPS (and all of the Geopilot II Plus cartridges) use the WGS84 datum, which is the model
of the earth that is the closest possible average of the planet as a whole. Your chart datum is usually