Generation of logistics development of the
vehicle, the ship transport form a breakthrough, in the first place. Temporary,
since the running vehicle because of the dispersed flow, information
communication is difficult, work condition is complicated, has been a
transportation enterprise management difficulties, if using satellite
positioning technology, computer network technology, GIS, GSM communication
technology to ensure the accuracy of the transportation scheduling, and then
integrated satellite data can be know the location of the receiver.
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| GPS Vehicle tracker XT-009 |
To achieve this purpose, the position of
the satellite can record according to the spaceborne clock time found in the
satellite ephemeris. While the user is the distance to the satellite
transmitted to the user experiences by recording the satellite's signal,
multiplied by the speed of light to get it again (because of the atmosphere,
the ionosphere disturbance, GPS tracker, this distance is
not the real distance between user and satellite, but the pseudorange (PR) :
when GPS satellite work normally, will continue to use the binary 1 s and 0 s
element consisting of pseudo-random code (pn code) launch navigation message.
GPS vehicle
tracker system using the pseudo code of A total
of two kinds, respectively is civil C/A code and P (Y) code for the military.
C/A code frequency 1.023 MHz, repeat cycle is A millisecond, code spacing of 1 millisecond,
equivalent to 300 m; P code frequency 10.23 MHz and 266.4 days, repeat cycle
code spacing 0.1 microseconds, equivalent to 30 m. And Y code is on the basis
of P code, secrecy performance is better. Navigation message includes satellite
ephemeris, working conditions, and clock correction, ionospheric delay
correction, correction of atmospheric refraction and other information. It came
from a satellite signal demodulation to 50 b/s on the carrier frequency
modulation launch. Navigation message contains five child frame each main frame
of the frame length 6 s. The first three frames each ten word; Repeat every 30
seconds, updated every hour
