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Glossary
Base: A reference station operated in static
mode.
Baseline: A three-dimensional vector con-
necting the base to the rover. The baseline
length is the vector modulus.
DGPS: Differential GPS. A technique where-
by data from a receiver at a known location is
used to correct the data from a receiver at an
unknown location. Differential corrections
can be applied in real-time or by post-pro-
cessing. Since most of the errors in GPS are
common to users in a wide area, the DGPS-
corrected solution is significantly more accu-
rate than a normal autonomous solution.
Direct IP: (IP=Internet Protocol) A way of ac-
quiring base data (corrections) from the In-
ternet via GPRS. When setting Direct IP in a
receiver, you must specify the IP address of
the corrections provider.
Fixed: Position solution status achieved by a
receiver operating successfully in RTK mode.
Position accuracy is in the order of one cen-
timeter.
Float: Intermediate position solution status
obtained in a receiver attempting to operate
in RTK mode. Position accuracy is also inter-
mediate as it is only in the order of a few
decimeters.
GNSS: Global Navigation Satellite System.
GPS, GLONASS and the future Galileo are
each a GNSS.
GPRS: General Packet Radio Service. A mo-
bile data service available to cell phone us-
ers. GPRS data transfer is typically charged
per megabyte of transferred data, while data
communication via traditional circuit switch-
ing is billed per minute of connection time,
independent of whether the user has actually
transferred data or he has been in an idle
state.
GPS: Global Positioning System. Passive,
satellite-based navigation system operated by
the Department of Defense of the USA. Its
primary mission is to provide passive global
positioning/navigation for land-, sea-, and air-
based operations.
GSM: Global System for Mobile communica-
tions. The most popular standard for mobile
phones in the world.
HRMS: Horizontal Root Mean Square. A sta-
tistical measure of the scatter of horizontal
computed positions about a “best fit” posi-
tion solution. It gives you a good indication of
how well the unit performs.
Initialization: • A process used at power-on to
help a GPS receiver more easily determine its
own location. The solution is of the GPS stan-
dalone type (accuracy is a few meters).
• For an RTK rover, once GPS initialization is
achieved, a process through which the receiv-
er can solve integer ambiguity from which it
can deliver a fixed solution with centimeter
accuracy.
NTRIP: Networked Transport of RTCM via In-
ternet Protocol. A protocol used by GNSS ser-
vice providers to deliver corrections from
their networks of reference stations. When
setting NTRIP in a receiver, you must specify
the mount point (an IP address) of the NTRIP
provider as well as your personal user profile.
PDOP: Position Dilution of Precision. This
number describes the geometry of the GPS
constellation. The lower this number, the bet-
ter the geometry of the constellation and the
better the quality of the position solution.
Rover: The mobile unit that you carry with
you during your field operations.
RTCM: Radio Technical Commission for Mar-
itime services. RTCM standards are used in-
ternationally for Differential Global
Navigation Satellite Systems and Electronic
Chart Systems.
RTK: Real Time Kinematic. An algorithm run
in a receiver that allows its position to be de-
termined in real time, with centimeter accu-
racy.
UHF: Ultra High Frequency band. Magellan
radio modems use this frequency band.
VRMS: Vertical Root Mean Square. A statisti-
cal measure of the scatter of vertical comput-
ed positions about a “best fit” position
solution. It gives you a good indication of how
well the unit performs.
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