The Glossary Of GPS(6)

The Glossary Of GPS Between Q-T

Quadrifilar Helix Antenna
A type of GPS antenna in which four spiraling elements form the receiving surface of the antenna. For GPS use, quadrifilar antennas are typically half-wavelength or quarter-wavelength size and encased in a plastic cylinder for durability.

RS-232
A serial input/output standard that allows for compatibility between data communication equipment made by various manufacturers.

Radio Technical Commission For Maritime Services (RTCM) Special Committee 104
A committee created for the purposes of establishing standards and guidance for interfacing between radio beacon-based data links and GPS receivers, and to provide standards for ground-based differential GPS stations.

RAIM
Receiver Autonomous Integrity Monitoring; A GPS receiver system that would allow the receiver to detect incorrect signals being transmitted by the satellites by comparing solutions with different sets of satellites.

Route
A group of waypoints entered into the GPS receiver in the sequence you desire to navigate them.

SA
See Selective Availability.

Search The Sky
A message shown when a GPS receiver is gathering satellite almanac data. This data tells the GPS receiver where to look for each GPS satellite.

Serial Communication
The sequential transmission of the signal elements of a group representing a character or other entity of data. The characters are transmitted in a sequence over a single line, rather than simultaneously over two or more lines, as in parallel transmission. The sequential elements may be transmitted with or without interruption.

See-Thru® Technology
A Garmin exclusive technology which allows the various Garmin fishfinders to hear both weak and strong signals simultaneously so as to identify fish returns under the toughest conditions: suspended in thermoclines or even hiding near structures.

Selective Availability (SA)
The random error, which the government can intentionally add to GPS signals, so that their accuracy for civilian use is degraded. SA is not currently in use.

SOG
See Speed Over Ground.

SONAR
A system using transmitted and reflected underwater sound waves to detect and locate submerged objects or measure the distance to the floor of a body of water. This technology is used in Garmin fishfinders and sounder products.

Space Segment
The satellite portion of the complete GPS system.

Speed Over Ground (SOG)
The actual speed the GPS unit is moving over the ground. This may differ from airspeed or nautical speed due to such things as head winds or sea conditions. For example, a plane that is going 120 knots into a 10-knot head wind will have a SOG of 110 knots.

Spread Spectrum
The received GPS signal is wide bandwidth and low power. The L-band signal is modulated with a pseudo-random noise code to spread the signal energy over a much wider bandwidth than the signal information bandwidth. This provides the ability to receive all satellites unambiguously and to give some resistance to noise and multipath.

Statute Mile
A unit of length equal to 5,280 feet or 1,760 yards (1,609 meters) used in the U.S. and some other English-speaking countries.

Straight-Line Navigation
The act of going from one waypoint to another in the most direct line and with no turns.

Time To First Fix (TTFF)
If you have not used your GPS unit for several months, the almanac data for the satellites may be out of date. The unit is capable of recollecting this information on its own, but the process can take several minutes. Time to First Fix (TTFF) is the time it takes a GPS receiver to find satellites after the user first turns it on (when the GPS receiver has lost memory or has been moved over 300 miles from its last location).

TracBack
The proprietary Garmin feature which takes your current track log and converts it into a route to guide you back to a starting position.

Track Up Orientation
Fixes the GPS receiver’s map display so the current track heading is at the top of the screen.

Track (TRK)
Your current direction of travel relative to a ground position (same as Course Over Ground).

Transducer
A device, much like a microphone, that converts input energy of one form into output energy of another. Fishfinders separate and enhance the information received from a transducer to show underwater objects.

Triangulation
A method of determining the location of an unknown point, as in GPS navigation, by using the laws of plane trigonometry.

TRK
See Track.

TRN
See Turn.

Troposphere
The lowest region of the atmosphere between the surface of the earth and the tropopause, characterized by decreasing temperature with increasing altitude. GPS signals travel through the troposphere (and other atmospheric layers).

True North
The direction of the north pole from your current position. Magnetic compasses indicate north differently due to the variation between true north and magnetic north. A GPS receiver can display headings referenced to true north or magnetic north.

TTFF
See Time To First Fix.

Turn (TRN)
The degrees which must be added to or subtracted from the current heading to reach the course to the intended waypoint.