Memorex RX 1 Smart Manual de instalación descargar pdf (Pagina 195)

Appendix E - Glossary | 193

REFERENCE ELLIPSOID

A mathematical description of the Earth’s ellipsoidal shape (see ELLIPSOID), which

is the reference frame for positioning computation.

REFERENCE GPS MONITOR

A GPS CDU whose precise (surveyed) position is known. It compares its own

GPS position solution to the surveyed position and generates correction values

as a function of the position coordinate differentials. The correction values are

transmitted to user GPS CDUs for use as corrections to their own GPS position

solu tions.

RESET

To return stored values to either the default value or zero in memory.

RHUMB LINE

The course of a vessel that keeps a constant compass direction, drawn as a line on

a chart or globe and cut ting across all meridians at the same angle. A rhumb line

is a straight line on a Mercator chart.

RHUMB LINE NAVIGATION

Navigation based on Rhumb Lines. See also GREAT CIRCLE NAVIGATION.

RMS

See ROOT MEAN SQUARED.

ROOT MEAN SQUARED (RMS)

A statistical measure of probability, stating that an expected event will happen

68% of the time. In terms of position update accuracy, 68 position updates out of

100 will be accurate to within specified system accuracy.

ROUTE

A route is a sequential list of waypoints describing a planned voyage. The active

route is the route used for the actual navigation of the vessel.

RTCM

Radio Technical Commission for Maritime Services.

S/A

See SELECTIVE AVAILABILITY

SATELLITE HEALTH

Go or no-go message for each satellite included in the almanac data. The

message states whether or not the measurements from those particular satellites

can be relied upon for accurate results.

SATELLITE SIGNAL

Transmitted electromagnetic energy from a GPS satellite whose time of arrival is

measured by the navigator to calculate the position of the navigator antenna.

SELECTIVE AVAILABILITY (S/A)

A system whereby the accuracy of GPS is reduced. S/A is controlled by the U.S.

Department of Defense.

SEMIMINOR AXIS

The distance from the center of the earth’s ellipse to the ellipse surface as

measured along the polar axis. It is identified symbolically with the letter B, and it

varies according to the reference datum used for position coordi nates.

SENSOR

A device that detects a change in a physical stimulus and turns it into a signal that

can be measured.

SET AND DRIFT

The direction and the speed of the water over ground (current).

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