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Residual
— in the context of measurement, the residual is the misclosure between the calculated
measurements, using the position solution and actual measurements.
RMS — root-mean-square, a probability level of 68%. This is true only for 1-D Gaussian distributions. For 2-
D or 3-D Gaussian Distribution, the percentage of the values distributed inside a circle (or sphere),
with a radius equal to the RMS value depends on distribution shape.
Roll — to move by turning on an axis or to rotate about its axis lengthwise, as an aircraft in flight.
Route — a planned course of travel, usually composed of more than one navigation leg.
Rover Receiver — the GPS receiver which does not know its position and needs to receive measurements from
a reference station to calculate differential GPS positions. (The terms rover and remote are
interchangeable.)
RT-10 — NovAtel's Double Differencing Technology for real-time kinematic (RTK) carrier phase floating
ambiguity resolution.
RTCA — Radio Technical Commission for Aeronautics, an organization which developed and defined a
message format for differential positioning.
RTCM — Radio Technical Commission for Maritime Services, an organization which developed and defined
the SC-104 message format for differential positioning.
RTK — real-time kinematic, a type of differential positioning based on observations of carrier phase. In this
document it is also used with reference to RT-20 and RT-10.
Satellite Constellation — The arrangement in space of a set of satellites. In the case of GPS, the fully
operational constellation is composed of six orbital planes, each containing four satellites.
GLONASS has three orbital planes containing eight satellites each.
Satellite elevation — the angle of the satellite above the horizon.
Selected waypoint — the waypoint currently selected to be the point toward which the vessel is travelling.
Also called "to" waypoint, destination or destination waypoint.
Selective Availability (SA) — the method used by the United States Department of Defence to control access
to the full accuracy achievable by civilian GPS equipment (generally by introducing timing and
ephemeris errors).
Sequential receiver — a GPS receiver in which the number of satellite signals to be tracked exceeds the
number of available hardware channels. Sequential receivers periodically reassign hardware
channels to particular satellite signals in a predetermined sequence.
Sidereal Day — the rotation period of the earth, and is equal to a calendar day minus four minutes
Space Segment — The portion of the GPS or GLONASS system that is located in space, that is, the GPS or
GLONASS satellites and any ancillary spacecraft that provide GPS or GLONASS augmentation
information (i.e., differential corrections, integrity messages, etc.)
Spherical Error Probable (SEP) — the radius of a sphere, centered at your true location, that contains 50
percent of the individual three-dimensional position measurements made using a particular
navigation system.
Spheroid — sometimes known as ellipsoid; a perfect mathematical figure which very closely approximates
the geoid. Used as a surface of reference for geodetic surveys. The geoid, affected by local gravity
disturbances, is irregular.
Standard Positioning Service (SPS) — a positioning service made available by the United States Department
of Defence which will be available to all GPS civilian users on a continuous, worldwide basis
(typically using C/A Code).
Static Positioning— Location determination accomplished with a stationary receiver. This allows the use of
various averaging or differential techniques.
GPS/GLONASS Receiver User Manual Rev 1
I GPS/GLONASS Glossary of Terms
121
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