User's Manual Part 1

Positioning Modes of Operation Chapter 5
OEMV Family Installation and Operation User Manual Rev 5B 95
RT-20 Performance
As shown in Table 20, RT-20 Performance below, Figure 31 on Page 96 and Figure 32 on Page 96
the RT-20 system provides nominal 20 cm accuracy (RMS) after 15 minutes of continuous lock in
static mode. After an additional period of continuous tracking (from 10 to 20 minutes), the system
typically reaches steady state. The time to steady state is about 3 times longer in kinematic mode.
RT-20 double-difference accuracies are based on PDOP < 2 and continuous tracking of at least 5
satellites (6 preferred) at elevations of at least 11.5°.
All accuracy values refer to horizontal RMS error, and are based on low-latency positions. The level
of position accuracy at any time will be reflected in the standard deviations output with the position.
Table 20: RT-20 Performance
Tracking
Time (s)
Mode
1
Data Delay
(s)
Distance
(km)
Accuracy (RMS)
1 - 180 Static 0 1 45 to 25 cm
180 - 3000 Static 0 1 25 to 5 cm
> 3000 Static 0 1
5 cm or less
2
1 - 600 Kinematic 0 1 45 to 25 cm
600 - 3000 Kinematic 0 1 25 to 5 cm
> 3000 Kinematic 0 1
5 cm or less
2
Either 0 - 2 1 +1 cm/s
Either 2 - 7 1 +2 cm/s
Either 7 - 30 1 +5 cm/s
Either > 30 1
pseudorange or single point
3
Either 0 0 - 10 +0.5 cm/km
Either 0 10 - 20 +0.75 cm/km
Either 0 20 - 50 +1.0 cm/km
1 Mode = Static or Kinematic (during initial ambiguity resolution)
2 The accuracy specifications refer to the BESTPOSA/B logs which include about 3 cm
extrapolation error. MATCHEDPOSA/B logs are more accurate but have increased
latency associated with them.
3 After 60 seconds reverts to pseudorange positioning (single point or differential
depending on messages previously received from the base station).