Module 2 : Global Positioning System
  Lecture 12 : GPS Measurements Techniques
GPS observables

Traditionally, 4 types of signal measurement approaches have been used for positioning with GPS:

(1) Pseudoranges from Code measurements
(2) Carrier Phases or Carrier Beat Phase or carrier differences
(3) Pseudorange differences from integrated Doppler counts
(4) Differences in signal travel time from interferometric measurements

Although all techniques have different characteristics, all are functions of instantaneous ranges between satellites, the ground station and their derivative. Generally, the code and pahse values are two most important observables. Hence, the first two methods are the main GPS measurement techniques which give rise to two types of GPS measurement models:

(1) Pseudorange model or code measurement model
(2) Carrier beat phase measurement model

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