u-blox ANTARIS 4, Руководство по системной интеграции

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4.5.2 Warmstart Strategy
In Warmstart, the receiver reads the approximate time (from RTC clock), position and almanac information from
4.5.3 Hotstart Strategy
te time (from RTC clock), position, almanac and ephemeris
rts to navigate.
ith poor/limited sky view or does not have a
backup battery. Depending on the information provided, the receiver will perform the best possible startup
scenario.
Battery Backup RAM, assigns up to 12 channels with currently visible SVs and tries to acquire them. The
remaining channels will be assigned to non-visible SVs as the receiver may have been moved to another location
during off time.
Once sufficient SVs are found and ephemeris is decoded, the receiver starts to navigate.
In Hotstart, the receiver reads the approxima
information from Battery Backup RAM, assigns up to 12 channels with currently visible SVs and tries to acquire
them. The remaining channels will be assigned to non-visible SVs as the receiver may have been moved to
another location during off time.
Once sufficient SVs are found the receiver sta
4.5.4 Aiding / Assisted GPS (AGPS)
The ANTARIS
®
4 aiding feature allows supplying external information to improve Time To First Fix (TTFF). This is
particularly useful if a receiver is operated in an environment w
Acquisition
Sync/
Confirm
Tracking
best case typ:
6-12 secs
Start
Receiver First
Position
(TTFF)
Time
Ch
an
nel
s
S
ig
n
al
Leve
l
Aiding Data
received
Figure 74: GP n isition with Ai ng
ites can improve the TTFF in urban canyons (downloading the
ephemeris requires a direct line-of-sight to each satellite for at least 18s, which is difficult to achieve for the low
areas). If not only the ephemeris but also current time and
the almanac too) are downloaded to the receiver, the TTFF can be
S Sig al Acqu di
Providing ephemeris data for the visible satell
elevation satellites in urban or mountainous
approximate receiver position (and possibly
further reduced as the receiver can skip certain steps during the acquisition procedure.
The minimal TTFF of about 4s is achieved by providing precise hardware time synchronization.
GPS Modules - System Integration Manual (SIM) (incl. Reference Design) Receiver Description
GPS.G4-MS4-05007-A1 Page 90