The GPS receiver can receive the time information that can be used to be
used for time -to -nano -seconds; it is used to predict the forecast star
calendar in the future of satellites in the next few months; , The accuracy is
several meters to tens of meters (different satellites are different, change at
any time); and GPS system information, such as satellite conditions.
The GPS receiving machine decodes or uses other technologies for the
receiving satellite signals. After removing the information on the carrier, the
carrier can be restored. Strictly speaking, the carrier phase should be called
the carrier frequency phase. It is the difference between the signal phase of
the satellite signal carrier of the Doppler frequency transparent and the
receiving machine. Generally, the number of times of calendar time determined by
the receiver clock and maintaining the tracking of satellite signals can record
the change value of the phase, but the initial value of the receiver and the
satellite oscillator when you start observation is unknown. The phase integer of
the original element is also unknown, that is, the fuzzyness of the week, and
can only be used as a parameter in data processing. The accuracy of the phase
observation value is as high as millimeter, but the premise is to solve the
fuzzyness of the entire week. Therefore, the phase observation value can be used
only when the relative positioning and a continuous observation value can be
used. Can use phase observation values.
The measurement of the GPS receiver can get the distance from the satellite
to the receiver. Because the error containing the receiver satellite clock and
the atmospheric dissemination error, it is called a pseudo -distance. The pseudo
-tagging distance from 0A is called UA code pseudo -pseudo -pseudo -pseudo
-pseudo -pseudo -pseudo -precision is about 20 meters. The pseudo -pseudo
distance from P code is called p code pseudo distance, and the accuracy is about
2 meters.
According to the positioning method, GPS positioning is divided into single
-point positioning and relative positioning (differential positioning). The
single -point positioning is to determine the position of the receiving machine
based on the observation data of a receiver. It can only use a pseudo -distance
observation capacity, which can be used for rough navigation positioning of
vehicles and boats. Relative positioning (differential positioning) is the
method of determining the relative position between the observation points based
on the observation data of the receiver of the two or more. Use phase
observation values for relative positioning.
In the GPS observation volume, the bell difference, atmospheric
transmission, and multi -path effects of satellite and receiving machines are
included in the GPS observation measurement. When the positioning is calculated,
the satellite broadcasting star calendar error should be affected. Cancel off or
weakening, so the positioning accuracy will be greatly improved. The dual
-frequency receiver can offset the main part of the ionization error of the
atmosphere in the atmosphere according to the observation of the two
frequencies. ), A dual -frequency receiver should be selected.
When the positioning observation, if the receiver is moved by the surface
of the earth, it is called dynamic positioning. If the accuracy of a rough
navigation positioning for vehicles and boats is a pseudo -distance single
-point positioning of 30 to 100 meters, or for urban vehicle navigation
positioning The pseudo -distance differential positioning of the rice -level
accuracy, or the centimeter -level phase differential positioning (RTK) used to
measure the sample, and calculate the observation data of two or more stations
in real time. When the positioning observation, if the receiver is static
relative to the surface of the earth, it is called a static positioning. When
the control network observation is performed, this method is generally observed
by several receivers at the same time. Positioning accuracy, which is dedicated
to this purpose, is called a earth -type receiver, and is the best performance
in the receiver. At present, GPS has been able to meet the accuracy requirements
of crustal transformation observation. IGS's perennial observation platform has
a global coordinate framework that can form a millimeter level.
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