u-blox ANTARIS 4, Руководство по системной интеграции

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your position is our focus
4.6.5 Degraded Navigation
ed navigation de Degrad vi use less than 4 satellites.
4.6.5.1 2D Navigatio
If the GPS receiver only s 3 satellite calculate a sition, the vigation a u a con altitude
ke u e missi e),
the altitude is kept cons
Note The ANTAR GPS Techn gy does not lculate any lution with numbe f SVs le 3 SV.
ANTARIS
®
4 Timing Receivers can calculate timing solution with only one SV.
Note s during acquisition, the initial altitude is set to 500m. To
change the tial altitude u UBX – CFG onfig) - NAV2 (Navigatio 2) mess .
4.6.5.2 Dead Reckon g/ extrapo ing position g
plemented extra r does no longer achieve a position fix
with a sufficient position accuracy or DOP value (can be configured in UBX-CFG-NAV2). It keeps a fix track
(heading i til the Dead Reckoning Timeout is reached. The position is
extrapolated but it’s indicated as “NoFix” (except for NMEA V2.1).
Note For sensor based Dead Reckoning GPS solutions, u-blox offers Dead Reckoning enabled GPS modules
racy position solutions for automotive applications at places
with poor or no GPS coverage. This technology relies on additional inputs from a turn rate sensor
(gyro) and a speed sensor (odometer or wheel tick).
T bit information less accurate than the information retrieved
f ng available, (e.g. while the ephemeris
s the
With almanac navigation enabl
il the ephemeris is fully retrieved. By disabling
almanac navigation, the receiver does not use the almanac for navigation, but will always wait to collect the
With an almanac only solution the position will only have an accuracy of a few kilometers. Normal GPS
performance requires at least 4 satellites included in the navigation solution, which have ephemeris information
available.
Almanac navigation allows much faster start up, as there is no need to wait for the completion of the ephemeris
download (>18s). This is useful whenever an inaccurate position is better than no position (e.g. emergency or
security devices).
Note The almanac information is NOT used for calculating a position, if valid ephemeris information is
present, regardless of the setting of this flag. But the almanac information is needed to acquire the
SV when there is no ephemeris data available.
scribes all na
n
gation modes, which
ha s to po na lgorithm ses stant
to ma p for th ng fourth satellite. When losing a satellite after a successful 3D fix (min. 4 SV availabl
tant to the last known altitude. This is called a 2D fix.
IS
®
4 olo ca so a r o ss than
Only
If the receiver makes initial 2D LSQ fixe
ini se (C n age
in lat in
The im polation algorithm kicks in as soon as the receive
s equal to the last calculated heading) un
(LEA-4R/TIM-4R). They allow high accu
4.6.6 Almanac Navigation
he satellite or retrieved from an almanac is much
a startup period, only almanac infor rom the ephemeris. If duri mation is
receiver still is able to navigate based on alman till is being downloaded) ac orbits.
ed, when a new satellite rises and its reception just has started, the receiver might
use an almanac to use this satellite in the navigation solution unt
entire ephemeris information before including a satellite in the navigation solution.
GPS Modules - System Integration Manual (SIM) (incl. Reference Design) Receiver Description
GPS.G4-MS4-05007-A1 Page 99