GPS satellite signals Each GPS satellite transmits signals on two frequencies called carriers: L1 =...
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Transcript of GPS satellite signals Each GPS satellite transmits signals on two frequencies called carriers: L1 =...
![Page 1: GPS satellite signals Each GPS satellite transmits signals on two frequencies called carriers: L1 = 1574.42 MHz sinusoidal : 19.05 centimeters L2 = 1227.60.](https://reader036.fdocuments.in/reader036/viewer/2022062309/5665b49d1a28abb57c92a983/html5/thumbnails/1.jpg)
GPS satellite signalsEach GPS satellite transmits signals on two frequencies called carriers:•L1 = 1574.42 MHz sinusoidal : 19.05 centimeters•L2 = 1227.60 MHz sinusoidal : 24.45 centimetersThe carrier PHASES are modulated by THREE pseudo-random binary codes •Coarse/acquisition code (C/A) : 1.023 MHz (293.1 meters) (L1 only)C/A random sequence repeats every millisecond•Precise code (P-code) : 10.23 MHz (29.31 meters) (L1 & L2)P-code sequence repeats every 266 days•Navigational code (50 Hz) (L1 & L2)
Cada satélite GPS transmite señales en dos frecuencias llamados portadores:•L1 = 1574.42 MHz sinusoidal: 19,05 centímetros•L2 = 1227.60 MHz sinusoidal: 24,45 centímetrosLas fases portadoras son moduladas por tres códigos binarios pseudo-aleatorios•Código Grueso / adquisición (C / A): 1.023 MHz (293,1 metros) (L1 solamente)•C / D secuencia aleatoria se repite cada milisegundo•Código precisa (código P): 10.23 MHz (29,31 metros) (L1 y L2)•Secuencia de código P se repite cada 266 díasCódigo de la Navegación (50 Hz) (L1 y L2)
Las señales de satélite GPS
![Page 2: GPS satellite signals Each GPS satellite transmits signals on two frequencies called carriers: L1 = 1574.42 MHz sinusoidal : 19.05 centimeters L2 = 1227.60.](https://reader036.fdocuments.in/reader036/viewer/2022062309/5665b49d1a28abb57c92a983/html5/thumbnails/2.jpg)
C(t) = C/A code (open to all users)P(t) = P-code (open to all users in peace time)D(t) = Navigation message
Note that P-code and C/A code modulate carrier frequencies 90 degrees out of phase (sine versus cosine)
Binary (0/1) P-code and C/A-code modulations can thus be separated from each other
P-code
Nav
Carriers
C/A code
Nav f1 + 90°
C (t) = C / A código (abierto a todos los usuarios)P (t) = P-código (abierto a todos los usuarios en tiempo de paz)D (t) = mensaje de navegación
Tenga en cuenta que el código P y C / D modulación de portadora código de frecuencias de 90 grados fuera de fase (sinusoidal frente coseno)
Binaria (0/1) de código P y modulaciones de código C / A de este modo se pueden separar el uno del otro
![Page 3: GPS satellite signals Each GPS satellite transmits signals on two frequencies called carriers: L1 = 1574.42 MHz sinusoidal : 19.05 centimeters L2 = 1227.60.](https://reader036.fdocuments.in/reader036/viewer/2022062309/5665b49d1a28abb57c92a983/html5/thumbnails/3.jpg)
P-code
Nav
Carriers
C/A code
Nav f1 + 90°
L1 and L2 phaseIs modulated byC/A, P-, and navBinary pseudorandom number codes
L1 y L2 faseEs modulada porC / A, P-y navegaciónCódigos de números pseudo-aleatorios binarios
![Page 4: GPS satellite signals Each GPS satellite transmits signals on two frequencies called carriers: L1 = 1574.42 MHz sinusoidal : 19.05 centimeters L2 = 1227.60.](https://reader036.fdocuments.in/reader036/viewer/2022062309/5665b49d1a28abb57c92a983/html5/thumbnails/4.jpg)
Building the GPS signalSatellites generate L1 & L2 frequency signalsL1 modulated by C/A, P, and navL2 modulated by P-code and navGPS receivers dissect and record L1, L2, P, & C/A signals
La construcción de la señal GPS
Los satélites generan señales de frecuencia L1 y L2L1 modulada por C / A, P y navegaciónL2 modulada por código P y navegaciónLos receptores GPS diseccionar y grabar L1, L2, P, C y señales / A
![Page 5: GPS satellite signals Each GPS satellite transmits signals on two frequencies called carriers: L1 = 1574.42 MHz sinusoidal : 19.05 centimeters L2 = 1227.60.](https://reader036.fdocuments.in/reader036/viewer/2022062309/5665b49d1a28abb57c92a983/html5/thumbnails/5.jpg)
![Page 6: GPS satellite signals Each GPS satellite transmits signals on two frequencies called carriers: L1 = 1574.42 MHz sinusoidal : 19.05 centimeters L2 = 1227.60.](https://reader036.fdocuments.in/reader036/viewer/2022062309/5665b49d1a28abb57c92a983/html5/thumbnails/6.jpg)
Finding sat-to-receiver distance from C/A or P-code
Encontrando sat-a-receptor distancia de C / A o P-codigo
![Page 7: GPS satellite signals Each GPS satellite transmits signals on two frequencies called carriers: L1 = 1574.42 MHz sinusoidal : 19.05 centimeters L2 = 1227.60.](https://reader036.fdocuments.in/reader036/viewer/2022062309/5665b49d1a28abb57c92a983/html5/thumbnails/7.jpg)
• Each GPS satellite has OWN unique C/A & P-code
• Each GPS receiver knows C/A and P-codes for ALL GPS satellites.
• Cada satélite GPS tiene su propio único / A & P-código C
• Cada receptor GPS sabe C / A y P-códigos para todos los satélites GPS.
![Page 8: GPS satellite signals Each GPS satellite transmits signals on two frequencies called carriers: L1 = 1574.42 MHz sinusoidal : 19.05 centimeters L2 = 1227.60.](https://reader036.fdocuments.in/reader036/viewer/2022062309/5665b49d1a28abb57c92a983/html5/thumbnails/8.jpg)
How precise are ranges found with C/A and P codes ?
• C/A code “chips” 1.023 million times per second
• P code chips 10.23 million times per second
• Average “chip” has wavelength of 300 meters for C/A code and 30 m for P code.
• Receiver can “line up” edges of the C/A and P “chips” to about 1%, or 3 meters for C/A and 30 cm for P.
¿Qué tan preciso rangos se encuentran los códigos C / A y P?
• Código C / A "chips" 1.023.000 veces por segundo
• Chips de código P 10.230.000 veces por segundo
• "Chip" Promedio tiene longitud de onda de 300 metros para el código C / A y 30 m para el código P.
• El receptor se "alinean" bordes de la C / A y "chips" P a aproximadamente 1%, o 3 metros para C / A y 30 cm para P.
![Page 9: GPS satellite signals Each GPS satellite transmits signals on two frequencies called carriers: L1 = 1574.42 MHz sinusoidal : 19.05 centimeters L2 = 1227.60.](https://reader036.fdocuments.in/reader036/viewer/2022062309/5665b49d1a28abb57c92a983/html5/thumbnails/9.jpg)
EXAMPLE RINEX DATA FILE: Code measurements
DATOS EJEMPLO RINEX ARCHIVO: mediciones de código
![Page 10: GPS satellite signals Each GPS satellite transmits signals on two frequencies called carriers: L1 = 1574.42 MHz sinusoidal : 19.05 centimeters L2 = 1227.60.](https://reader036.fdocuments.in/reader036/viewer/2022062309/5665b49d1a28abb57c92a983/html5/thumbnails/10.jpg)
Code ranges: ρC/A = c •ΔtC/A-code ρP= c • ΔtP-code
rangos Código
rangos Código: ρC/A = c •ΔtC/A-code ρP= c • ΔtP-code
![Page 11: GPS satellite signals Each GPS satellite transmits signals on two frequencies called carriers: L1 = 1574.42 MHz sinusoidal : 19.05 centimeters L2 = 1227.60.](https://reader036.fdocuments.in/reader036/viewer/2022062309/5665b49d1a28abb57c92a983/html5/thumbnails/11.jpg)
Compare ranges from P-code to C/A CODE
P2 range - C/A range = c • ΔtP2 – L1 cycles • 0.1905 m/cycle
Range difference of 10 to 15 meters
Comparar gamas de código P para el grupo C / D CODE
P2 - C / A rango = c • ΔtP2 - ciclos L1 • 0,1905 m / ciclo
Rango de diferencia de 10 a 15 metros
![Page 12: GPS satellite signals Each GPS satellite transmits signals on two frequencies called carriers: L1 = 1574.42 MHz sinusoidal : 19.05 centimeters L2 = 1227.60.](https://reader036.fdocuments.in/reader036/viewer/2022062309/5665b49d1a28abb57c92a983/html5/thumbnails/12.jpg)
EXAMPLE RINEX DATA FILE: Phase measurements
DATOS EJEMPLO RINEX ARCHIVO: mediciones de fase
![Page 13: GPS satellite signals Each GPS satellite transmits signals on two frequencies called carriers: L1 = 1574.42 MHz sinusoidal : 19.05 centimeters L2 = 1227.60.](https://reader036.fdocuments.in/reader036/viewer/2022062309/5665b49d1a28abb57c92a983/html5/thumbnails/13.jpg)
Phase (cycle) counts for L1 and L2
L1 & L2 wavelengths of 19.05 and 24.45 cm
Satellite signal lostby GPS antenna
Fase (ciclo) cuenta para L1 y L2 L1 y L2 longitudes de onda de 19,05 y 24,45 cm
Señal de satélite Fase perdidopor la antena GPS
![Page 14: GPS satellite signals Each GPS satellite transmits signals on two frequencies called carriers: L1 = 1574.42 MHz sinusoidal : 19.05 centimeters L2 = 1227.60.](https://reader036.fdocuments.in/reader036/viewer/2022062309/5665b49d1a28abb57c92a983/html5/thumbnails/14.jpg)
Comparison of ranges from L1 and L2 phase counts
Difference = 0.2445 m/cycle • L2 cycles - 0.1905 m/cyc • L1
cycles
Difference only 0-5 meters after fixing the L2 cycle slip
Comparación de los rangos de los recuentos de fase L1 y L2
Diferencia = 0,2445 m / ciclo ciclos • L2 - 0.1905 m / cyc ciclos • L1
Diferencia sólo 0-5 metros después de la fijación del deslizamiento de ciclo L2
![Page 15: GPS satellite signals Each GPS satellite transmits signals on two frequencies called carriers: L1 = 1574.42 MHz sinusoidal : 19.05 centimeters L2 = 1227.60.](https://reader036.fdocuments.in/reader036/viewer/2022062309/5665b49d1a28abb57c92a983/html5/thumbnails/15.jpg)
Conclusion thus far
• With few or no corrections to the observations,
Can determine ranges to 10-15 meters from C/A and P codes.
Can determine ranges to 0-5 meters from L1 and L2
To estimate positions to better than 0.01 meters, must improve the range accuracies by more processing of the GPS observables.
Conclusión
• Con pocas o ninguna las correcciones a las observaciones, Puede determinar los
intervalos de 10 a 15 metros de C / A y P correspondientes.
Puede determinar los intervalos de 0-5 metros de L1 y L2
Para estimar posiciones para mejor que 0.01 metros, debe mejorar la precisión de rango por más procesamiento de los observables GPS.