Topcon America Corporation 090531 ユーザーズマニュアル

HiPerII Chapter 1 

 
Achieving quality position results requires the following elements: 

  Accuracy - The accuracy of a position primarily depends upon the satellite geometry 

( Geometric Dilution of Precision, or GDOP ) and the measurement (ranging) errors. 

  Differential positioning ( DGPS and RTK ) strongly mitigates atmospheric and orbital 

errors, and counteracts Selective Availability ( SA ) signals the US Department of 
Defense transmits with GPS signals. 

  The more satellites in view, the stronger the signal, the lower the DOP number, the 

higher positioning accuracy. 

  Availability - The availability of satellites affects the calculation of valid positions.  The 

more visible satellites available, the more valid and accurate the position.  Natural and 
man-made objects can block, interrupt, and distort signals, lowering the number of 
available satellites and adversely affecting signal reception. 

  Integrity - Fault tolerance allows a position to have greater integrity, increasing accuracy.  

Several factors combine to provide fault tolerance, including: 

  Receiver Autonomous Integrity Monitoring ( RAIM ) detects faulty GNSS satellites and 

removes them from the position calculation. 

  Five or more visible satellites for only GPS or only GLONASS;  six or more satellites 

for mixed scenario 

  Satellite Based Augmentation Systems ( WAAS, EGNOS, and so on ) creates and 

transmit, along with DGPS corrections,  data integrity information ( for example, 
satellite health warnings ). 

  Current ephemerides and almanacs. 

 

 
This overview simply outlines the basics of satellite positioning.    For more detailed information, 
visit the 

Sokkia Topcon

 website. 

 

 
When power is turned on and the receiver self-test completes, the receiver's 72 channels 
initialize and begin tracking visible satellites.  Each of the receiver's channels can be used to 
track any one of the GPS or GALILEO signals.  The number of channels available allows the 
receiver to track all visible global positioning satellites at any time and location.