R

Radio Direction Finder

A radio receiver that features a directional antenna and a visual null indicator for use in determining lines of position from radiobeacons at known positions

Radio Frequency (RF)

Radio frequency refers to a signal generated by a radio transmitter and sent out through an antenna. The frequency of the transmission is described in terms of the number of cycles per second or Hertz (Hz). A radio would be tuned to this frequency in order to receive the transmission. A radio signal is sometimes referred to by its initials, "RF"

RAIM

Receiver Autonomous Integrity Monitoring. A technique whereby the redundant information available at a GNSS receiver is autonomously processed to monitor the integrity of the navigation signals

Range

A fixed distance between two points, such as between a starting and an ending waypoint or a satellite and a GPS reciever

Ranging

A technique used to determine a line of position by calculating the distance between a receiver and a known reference point

Raster

Computer graphics term describing a predetermined pattern of line that provides uniform coverage of a display space

Real Time Kinematic (RTK)

The DGPS procedure whereby carrier phase corrections are transmitted in real time from a reference station to the user's roving receiver

Real-time differential GPS

A base station which computes, formats, and transmits corrections usually through some sort of data link (e.g. VHF radio or cellular telephone) with each new GPS observation. The roving unit requires some sort of data link receiving equipment to receive the transmitted GPS corrections and get them into the GPS receiver so they can be applied to its current observations

Real-Time Kinematic (RTK)

The DGPS procedure whereby carrier-phase corrections are transmitted in real time from a reference receiver to the user's receiver. RTK is often used for the carrier-phase integer ambiguity resolution approach

Receiver Autonomous Integrity Monitoring (RAIM)

A technique by which a GPS receiver system detects incorrect satellite signals by comparing solutions with different sets of satellites

Receiver-Independent Exchange (RINEX)

A set of standard definitions and formats to promote the free exchange of GPS data and facilities the use of data from any GPS receiver with any software package. The format includes definitions for time, phase, and range

Reference Station

A ground station at a known location used to derive differential corrections. The reference station receiver tracks all satellites in view, computes their pseudoranges, corrects these for errors, and then transmits the corrections to users

Relative Accuracy

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

Relative Positioning

The determination of relative positions between two or more receivers which are simultaneously tracking the same GPS signals

Relative Precision

Precision is defined as a measure of the tendency of a set of numbers to cluster about a number determined by the set (e.g. the mean). The usual measure is the standard deviation with respect to the mean. Relative precision denotes the tendency for the various components (X, Y, Z) between one station and other stations in the network to be clustered about the adjusted values

Reliability

The ability to perform a specific function without failure under specified conditions for a given length of time

Relief

Changes in terrain; elevations or depressions in the land

Relief shading

A technique for showing the ups and downs of the land portrayed on a topographic map. The process makes land look three-dimensional by the use of graded shadow effects. Traditionally, maps are shaded as though the light source is coming from the northwest

Rhumb Line

A line that passes through all meridians at the same angle. When drawn on a Mercator chart, the rhumb line is a straight line, because the Mercator chart is a distortion of a spherical globe on a flat surface. The rhumb line results in a longer course than a great circle route

RINEX

Receiver INdependent EXchange format. A set of standard definitions and formats to promote the free exchange of GPS data and facilities the use of data from any GPS receiver with any software package. The format includes definitions for time, phase, and range

RMS

Root Mean Square. The standard deviation of the error in the GPS location

RNP

Required Navigation Performance standards.

Rover

Any mobile GPS receiver collecting data during a field session. The receiver's position can be computed relative to another, stationary GPS receiver

RS232

The electronic voltage and timing interface definition for the connection of electronic equipment

RTCM

Radio Technical Commission for Maritime Services Commission set up to define a differential data link to relay GPS correction messages from a monitor station to a field user

RTK OTF

Real-Time Kinematic (RTK) On-The-Fly (OTF) positioning. A DGPS technique for high precision positioning of moving objects