GPSGPS

GPS Original Design

Started development in the late 1960s as NAVY/USAF project to replace Doppler positioning systemAim: Real-time positioning to < 10 meters, capable of being used on fast moving vehicles.Limit civilian (non-authorized) users to 100 meter positioning through the use of Selective Availability (SA).

GPS Design

Innovations:Use multiple satellites (originally 21,now 28)All satellites transmit at same frequencySignals encoded with unique code bi-phase ,quadrature code generated by pseudo-(designated by PRN, PR number): spectrum transmission.Dual frequency band transmission:L1 ~1.5 GHz, L2 ~1.25 GHz

3.1 GPS GPS

GPSPC/APC/A2mPC/A2PSK

GPSf0=10.23MHzGPS

GPSCarrierL1L2Ranging CodeC/AL1P(Y)L1L2P1P2 MessageGPS

GPS f010.23MHz

GPS

L1 154f0 = 1575.43MHz19.03cmL2 120f0 = 1227.60MHz24.42cmL5 115f0 = 1176.45MHz25.48cm

GPS2000~2010 1996GPSIGEBIGEB19971998GPSGPSGPSORDOperational Requirements DocumentGPS19991GPS200052SAGPS

GPS

GPS

10-11

FMAMPM

GPS

SiL1(t)AP(Pi(t) Di(t))cos(L1t1)Ac(Ci(t) Di(t))sin(L1t1) SiL2(t)BP(Pi(t) Di(t))cos(L2t2)APACBPL1(1575.42MHz)L2(1227.6 MHz)Pi(t) Gi(t)Di(t)iGPSPC/ADL1L2L1L212iGPSL1L2SiL1(t) SiL2(t)

2.

11

2+1-1+1+1

GPS1L L11575.42M 19.03cm L21227.6M 24.42cmL GPS2

PRN Pseudo Random Noise01/nn12

Pseudo Random Noise CodeReceiver PRNSatellite PRNTime Difference

GPSu(t)GPSu(t) u(t)u(t)R(t) 0u(t)u(t)R(t) =1

3

D2C/AP50bit/sC/APDP (S/N)(S/N)f/FFff/FDC/AP

GPS

1GPSGPSGPSmLPaLPa LPXLPaLPbGPS

2.GPSGPSC/APY1C/A GOLD102Nu=210-1=1023tu=1/f1=0.97752s, f1f01011.023 MHz,293.1mTu= Nutu=1ms1.023Mbit/s299.792Km;C/A300KmC/A10235020.5s10012.9m

C/A

2PPC/A24 Nu2.351014tu=1/f0=0.097752s29.3mTu= Nutu 267(38)10.23Mbit/s P267P3876.19 10121532PPC/APPC/A1/101/1000.29mP

P

C/AC/APPC/A1C/AP

Combined signal

Combined signal

In the combined signal, P-code is written 90 degrees out of phase with the C/A code (quadrature). Also has half the power but this is not critical to operation of system.Although, all satellites transmit at the same frequency the code differences allow them to be separated. It also means that you can track satellites knowing only the C/A code and the Y-code (as we have at the moment).

3Da.b.1500bit50bit/s30sc.5d.1030bit300e.123452545

3.2 GPSGPS

1500bit5300bit50bits30s25125min

TLM Telemetry Word11~89~22232425~30HOW Hand Over Word2ZCAP

13~10WN GPS GPS1980-1-6L2 10C/A01P(Y)N URATGD

AODC

a0a1a2

233~10GPS AODE

453~10GPS12.525)

3.3 GPSWGS84

1234WGS84

GPS-X-iZ-k

GPS-

t

GPS-

GPS-

GPS-

GPS

GPS-* 2004 1 15 0 0 0.00000000P 1 5945.509635 15759.608404 20698.949374 324.533285P 2 1141.101111 22665.359989 14690.489309 -257.156064P 3 -10344.447068 24021.826531 -3968.233325 77.825932P 4 22798.349665 -6520.820872 12310.795279 -43.522805P 5 -12628.924903 -23445.674881 -1192.036791 13.422888P 6 -13958.380086 -7542.103497 21489.237683 -2.952584P 7 18939.291158 -12511.028058 -13257.166627 635.667094P 8 26246.825668 -918.226411 -5165.342142 383.670428

GPS-t

GPSXkYkZk

3.4 GPSGPSGPSGPS

Third Component of GPS: User SegmentUser segment comprises receivers that have been designed to decode signals transmitted from satellites for purposes of determining position, velocity or time. Receiver must perform the following tasks: select one or more satellites in view acquire GPS signals measure and track signal recover navigational data

GPS1GPS234**5XYZ

PTKGPSL1L1L2

L1L2C/APYL1L2 L1C/AL1C/AL1/L2C/APL1/L2C/AP/YGPS

GPS

2GPS-LNA

GPS-

LNA

10MHzTCXO

GP2015

GP2021

ARM7

TX/RX

GPS/GPSL11575.42MHzC/A

GPS

1GPSGPSGPS1)

GPS GPS

GPS

GPS

2)

GPSGPS20000km-50~-180dB-30dBGPS

2GPSLGPS GPS

GPS

GPSGPSGPS4CA

GPSRAM12v

GPSGPSGPSGPS1.PDOP

2.GPS

RINEXGPS

3.

RTKRTDGPS4.GPSGPS

WGS-845.GPS

6.GISGPSGPSGPS

GPSDGPSLADGPSWADGPS