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GPS Measurement Method
Source: | Author:Marten Hong | Publish time: 2017-10-27 | 1489 Views | Share:
GPS and difference technique are used in real time and measurement after, speed static technique is only used in measurement after.
      GPS and difference technique are used in real time and measurement after, speed static technique is only used in measurement after.


Real time kinematics (RTK)

     
RTK usually need five or more than five satellite to measure the phase of base station and rover.

      It is necessary to initialize before measuring in order to acquire centimeter accuracy.

      If you use single frequency receiver, the early sub-kinematics required the rover to be placed on the known point to create a man-made base line to initialize the measurement. Now the single frequency RTK can realize auto initialization, only the time is longer compared with the du frequency RTK, and more easy to miss lock.

      If you use dual frequency receiver to do the kinematic measurement (that is RTK), the initialization time can be greatly shorten, what’s more, the initialization can be processed during movement, (that is OTF, which means On the Fly)

      If the satellites received are less than four during the measurement, you need to reinitialize when the satellite number increases to four or more than four.


Difference Globe Position System
DGPS

      DGPS technique uses GPS codeC/A codeto position. It is not necessary to initialize or continuously track the satellites. The measurement accuracy is only one to three meter.

      If the carrier wave added to the distance is smooth enough, the DGPS can reach to the sub-meter accuracy.


Static and quick static

      Static measurement can be used in the highest accuracy measurement, but the time needed is usually from 30 minutes to 15 hours, according to the length of the line. Static and Quick Static both need process after to acquire the accurate result.

      Quick static is one method of process after, the accuracy can reach to centimeter level. It takes at Least 8 minutes (normally 8-30 minutes) to measure by carrier wave measurement, according to The receiver type, base line length, available satellites units and geometry shape of satellite.

      You can use single frequency and dual frequency receiver to do the static measurement and the quick Static measurement.