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Operation Chapter 3
AG-STAR User Manual Rev 2 25
3.4.4 Configuration Notes
For compatibility with other GNSS receivers, and to minimize message size, it is recommended that you use
the standard form of RTCA, RTCM, RTCMV3 or CMR corrections as shown in the previous base and rover
examples. This requires using the INTERFACEMODE command to dedicate one direction of a serial port to
only that message type. When the INTERFACEMODE command is used to change the mode from the
default, NOVATEL, you can no longer use NovAtel format messages.
If you wish to mix NovAtel format messages and RTCA, RTCM, RTCMV3 or CMR messages on the same
port, you can leave the INTERFACEMODE set to NOVATEL and log out variants of the standard correction
messages with a NovAtel header. ASCII or binary variants can be requested by simply appending an "A" or
"B" to the standard message name. For example on the base station:
interfacemode com2 novatel novatel
fix position 51.11358042 -114.04358013 1059.4105
log com2 rtcm1b ontime 2
Using the receiver in this mode consumes more CPU bandwidth than using the native differential messages
as shown in Section 3.4.1, Base Station Configuration on page 23.
At the rover station you can leave the INTERFACEMODE default settings (interfacemode com2 novatel
novatel). The rover receiver recognizes the default and uses the corrections it receives with a NovAtel
header.
The PSRDIFFSOURCE command sets the station ID values which identify the base stations from which to
accept pseudorange corrections. This is a useful command when the rover station is receiving corrections
from multiple base stations. Refer to An Introduction to GNSS for more information on SBAS, available from
our web site at: www.novatel.com/an-introduction-to-gnss/
.
All PSRDIFFSOURCE entries fall back to SBAS (even NONE) for backwards compatibility.
At the base station it is also possible to log out the contents of the standard corrections in a form that is easier
to read or process. These larger variants have the correction fields broken out into standard types within the
log, rather than compressed into bit fields. This can be useful to modify the format of the corrections for a
non-standard application or to look at the corrections for system debugging purposes. These variants have
"DATA" as part of their names (for example, RTCADATA1, RTCMDATA1, CMRDATAOBS, and more). Refer
to the OEMStar Firmware Reference Manual
for detailed descriptions of the various message formats.
Information on how to send multiple commands and log requests using Windows, can be found on our web
site at www.novatel.com/support/known-solutions/
.
3.5 GLIDE
NovAtel’s GLIDE is an optional feature on the AG-STAR. GLIDE is a positioning algorithm for single
frequency GPS and GPS/GLONASS applications. GLIDE produces a smooth position output tuned for
applications where optimal time relative (pass to pass) accuracy is more important than absolute accuracy.
Because of this, it is well suited for agricultural applications.
Multipath signals tend to induce time-varying biases and increase the measurement noise on the L1
pseudorange measurements. Carrier phase measurements are much less susceptible to the effects of
multipath. The GLIDE algorithm fuses the information from the L1 code and the L1 phase measurements into
a Position-Time-Velocity (PVT) solution.
GLIDE includes settings for a dynamic mode, a static mode, and an “auto” mode, where the filtering
parameters are automatically adjusted as vehicle velocity varies between stationary and dynamic states.
GLIDE is an optional feature on the AG-STAR. You must order a GLIDE capable model to use
this feature.