NavCom StarUtil-3000 Rev.G - Manual (Page 97)

StarUtil 3000 User Guide – Rev G
6-95

The position rate setting sets the output of the NCT Binary message PVT1B and
the NMEA messages GGA, RMC, and VTG, provided that those messages are set
to ONCHANGE.
The NCT Binary message MEAS1B does not follow the position rate. To match a higher
position rate, the user must schedule the output of MEAS1B. The rate must be a
purchased position and raw data rate.

The [PROCESSRATE] command is used to query the rate at which the navigation
solution and measurement solutions are updated.
[PDOPLIMIT]
This command sets the maximum position dilution of precision (PDOP) allowed for a valid
navigation solution. For example, [PDOPLIMIT] 10 sets the PDOP limit to 10. If the satellites
available for navigation have a geometry that results in a PDOP value that exceeds this limit,
the receiver will report that a navigation solution is not available.

The default setting for [PDOPLIMIT] is 10. When the PDOP reaches higher values,
large errors can occur in the navigation solution. If the PDOP limit is set too low,
availability of the navigation solution may decrease.
NavCom’s specifications are
valid for a PDOP of

4.0.

The quality of GNSS data is dependent on the geometry between the receiver and
satellites; this includes the number of satellites that can be "seen" by the receiver
and the angle between the receiver and satellites as a constellation seen by the
receiver.
A satellite near the horizon usually provides a lower quality signal because of greater
atmospheric interference and the increased likelihood of the signal reflecting from
surface features; this is known as "multipath" error. The effect of geometry on GNSS
quality is measured by PDOP (position dilution of precision). PDOP is the overall
measure of the precision obtainable with a given satellite geometry. For example, a
PDOP of 4 or less yields excellent precision, a PDOP between 5 and 7 is acceptable
and a PDOP of 7 or more is considered poor.
[GEOIDALMODEL]GGM02
This command selects the GGM02 geoidal database. In the initial release v1.0.0.4, GGM02 is
not maintained as the Geoid Model through a receiver power cycle. This is corrected in later
releases. Loading a user profile that includes this command is a quick way to reset GGM02 as
the Geoid Model. Refer to Chapter 4/
Upload The GGM02 Database .

Only two types of Geoidal models may be loaded in the SF-3050: GGM02 and
GEOIDAL99. The GGM02 geoidal database is factory loaded. The user may define
a GEOIDAL99 database and load it into the receiver. The GEOIDAL99 model is
typically more precise than the GGM02 model. If loaded, it is typically preferred.
When the DEFAULT keyword is used, the receiver automatically selects the
Geoidal model according to this default priority list: GEOIDAL99, GGM02, NONE.
The model listed first, GEOIDAL99 is used if it is loaded in the receiver; otherwise,
the next model, GGM02, is used if it is loaded. If neither Geoidal model is loaded,
NONE is selected. The sequential order of the priority list cannot be changed by the
user. The GEOIDAL99 model is listed first because it typically provides the highest
precision.