u-blox ANTARIS 4 - Assisted GPS; A-GPS; DGPS (Differential GPS)

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1.8 Assisted GPS / A-GPS
AssistedGPS,orA-GPS,isatechnologythatusesanassistanceservertocut downthetimeneededtodetermine
alocationusing
GPS.Itisusefulinurbanareas,whentheuserislocatedin"urbancanyons",underheavytree
cover,orevenindoors.Itisbecomingmorecommonandit'scommonlyassociatedwith
LocationBasedServices
(LBS)overcellularnetworks.Figure25depictsatypicalA-GPSsystem.
GPS Satellites
GPS
Receiver
Receiver
Mobile Device
Base
Station
Aidin g
Server
Assistance Server
Radiolink, e.g.GSM
With GPSReceiver
GPSSatellites
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Figure 25: Aiding Topology
1.9 DGPS (Differential GPS)
Differential GPS (DGPS) provides slightly better accuracy than a stand-alone GPS receiver. The correction data
fromareferencestationis transmittedtotheGPSreceiverin orderto eliminatePseudorangeerrors. Additional
hardwareisrequiredtoreceivethesedata.
 when the Selective Availability (SA) was discontinued in May
 2000. These days, the
applicationsofDGPSaretypicallylimitedtosurveying
DGPS lost significance
GPSModules-SystemIntegrationManual(SIM)(incl.ReferenceDesign) GPSFundamentals
GPS.G4-MS4-05007-A1
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