Oceaneering C-NavX1 User Manual page 100

Absolute Positioning is the ability of a GNSS receiver to produce positional values without another receiver f or
ref erence.
Accuracy is the degree of conformity of a measured or calculated quantity to a standard or true value. Accuracy
is theref ore related to the quality of the results.
Almanac is f ound in subf rame 5 of the Navigation Message. It is a data f ile that helps the receiver track and
lock-on to satellites as it contains a summary of orbital parameters f or all GPS satellites. The almanac can be
acquired f rom any GPS satellite.
Almanac Files an almanac f ile contains orbit inf ormation, clock corrections, and atmospheric delay parameters
f or all satellites tracked. It is transmitted to a receiver f rom a satellite and is used by mission planning sof tware.
Altitude is the vertical distance above the ellipsoid or geoid. It is always stored as height above ellipsoid in the
GNSS receiver but can be displayed as height above ellipsoid (HAE) or height above mean sea level (MSL).
Ambiguity is the unknown number of whole carrier wavelengths between satellite and receiver.
Antenna is a device used to collect and amplif y the electromagnetic GNSS signals broadcast by a satellite.
These electromagnetic waves are then converted into electrical currents that are decoded by the receiver. Patch
or Microstrip antennas are most commonly used in GNSS.
Antenna Phase Center (APC) is the point in an antenna where the GNSS signal f rom the satellites is received.
The height above ground of the APC must be measured accurately to ensure accurate GNSS readings. The
APC height can be calculated by adding the height to an easily measured point, such as the base of the antenna
mount, to the known distance between this point and the APC.
Antispoofing (A/S) is an encryption technique developed by the US Department of Def ense (DoD) that when
implemented, denies access to the P-Code by any unauthorized users. With Antispoofing on, the user will need
a DoD issued "key" in order to gain access to the P-Code.
Apogee is the point in the orbit of a satellite about the earth that is the greatest distance f rom the center of the
earth.
Autocorrelation in ref erence to code is a plot of the scalar product of the noise sequence with a delayed copy
of itself .
Autonomous positioning (GNSS) is a mode of operation in which a GNSS receiver computes position f ixes in
real time f rom satellite data alone, without ref erence to data supplied by a ref erence station or orbital clock
corrections. Autonomous positioning is typically the least precise positioning procedure a GNSS receiver can
perf orm, yielding position f ixes that are precise to 100 meters with Selective Availability on, and 30 meters with
S/A of f .
Average Deviation is a measure of variability in a data set but it is more robust than standard deviation. It is
not related to the bell-shaped curve. It is the average of the absolute deviations of the values f rom the mean.
The data values are subtracted f rom the mean p roducing a list of deviations f rom the mean. The deviations are
not squared like they are f or the standard deviation; the absolute values of the deviations are used.
Azimuth the azimuth of a line is its direction as given by the angle between the meridian and the line measured
in a clockwise direction f rom the north branch of the meridian.
Bad Packets ref er to the number of bad C-Nav Correction Service (CCS) packets received since the unit was
turned on.
Bandwidth is a measure of the width of the f requency spectrum of a signal expressed in Hertz.
CNAV-MAN-061
Revision B
C-NavX1 GNSS Receiver User Manual
DOC-TEM-28-NUM Rev A Uncontrolled copy when printed
C-Nav
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