Hardware og software
Navigation hardware
The navigation unit uses a GPS receiver
optimised for car navigation. A Dead
Reckoning Unit is used to supply position
data when the GPS receiver is unable to
supply valid position data. An optional
RDS differential receiver can be added to
apply correction signals for improved ac-
curacy.
avigation Unit
Dead Reckoning
Unit
Corr. data
RDS Receiver
Astec
OEM-4000
( optional )
And Gate
GPS Receiver
U-Blox
Sirf Technology
TX
TX
The Dead reckoning unit takes over when
signal conditions are unreliable, for in-
stance when driving through a tunnel.
The differential correction signal reduces
the position error from worst-case 25 me-
ters to approximate 5 meters.
The SiRFstar Architectures
SiRF has incorporated the full complexity of GPS technology into its SiRFstar™
architectures, SiRFstarI and SiRFstarII. While both these architectures deliver
features specifically aimed at the consumer GPS market, SiRF’s GPS product
families based on these architectures each address a different kind of GPS-
enabled product.
Common to both SiRFstar architectures are a number of technologies aimed at
overcoming the technical challenges of applying GPS to consumer applications.
These SiRF technologies include the following:
SnapLock™ acquisition offers a satellite re-acquisition time of about one-
tenth of a second - as much as 20 times faster than other solutions. This capa-
bility is critical to establishing accurate positioning in urban canyon-type envi-
ronments where satellite visibility is intermittent.
SnapStart™ technology, which enables a GPS receiver to obtain a position
fix at the push of a button (less than 2 seconds), instead of the 15+ seconds,
required by traditional receivers.
SingleSat™ positioning mode which lets SiRFstar-enabled auto navigation
systems continue to update positioning information when only a single satel-
lite’s signal is detectable. Other GPS solutions require three or more satellite
signals to update a position.
Dual Multipath Rejection capability reduces multipath errors significantly.
Multipath errors caused by reflected signals are a major problem in urban areas
FoliageLock™ reception lets SiRFstar-enabled receivers maintain contact
with satellites while under dense foliage, thus providing reliable location
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