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Fig. 2: GPS Receiver Cost Trend 
3. ACHIEVABLE ACCURACIES AND 
OPERATING MODES 
Achievable accuracies using GPS are generally 
dependent on the type of receiver selected, the 
measurement utilized (i.e. code versus carrier 
phase, single point versus differential), as well as 
the dynamic environment (i.e. static versus 
kinematic land, marine or airborne). This paper is 
not intended to overview all the above in detail, 
however the major accuracies are summarized in 
Table 2. 
The table is sub-divided between single point and 
differential modes. Single point positioning is 
limited by the GPS system itself and is at the 
level of 100 m horizontally and 156 m vertically. 
Due to this limitation, single point positioning is 
not dependent on the receiver used, assuming C/A 
code technology. Differential accuracies are 
determined by the type of observable used, i.e. 
code (pseudorange), carrier phase, or a combination 
of both. For the case when the code measurements 
are used, accuracies are at the level of 2-9 m 
horizontally and 3-11 m vertically. The lower end 
of the scale is for the new generation of narrow 
correlator C/A code receivers which have a C/A 
code resolution of 10-20 cm (e.g. Van Dierendonck 
and Fenton, 1992) whereas the higher end is for 
standard C/A code receivers. These accuracies can 
be achieved in static or kinematic mode. 
165 
With the addition of carrier smoothing of the 
code, the achievable accuracy is improved. Tests 
have shown that accuracies at the level of 1-2 m 
can be achieved using narrow correlator C/A code 
receivers and 1.5-4 using standard C/A code 
technology. 
Table 2: C/ A Code GPS Achievable Accuracies 
  
  
  
  
  
Monitor 
Mode to Remote Accuracy 
Separation 
Single N/A Horiz: 100 m 
Point Vert: 156 m 
Horiz: 2to9m 
Differential Sükm - Mei -o340dim 
ode 
€ 500 km Horiz: 5tollm 
Vert: 6 to 12m 
Horiz: 1to3m 
50 km 
Differential Vert: 1to4 m 
Smoothed Code ; 
500 km Horiz: 3to9m 
Vert: 4 to 10 m 
Horiz: 0.05 to 0.3 m 
50 km 
Differential Vert: 0.1 to 0.5 m 
Carrier Phase ; 
500 km Horiz: 1to4m 
Vert: 2to6m