NavCom StarUtil-3000 Rev.A - Manual (Page 61)

StarUtil-3000 User Guide – Rev A
6-59
[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 .
[2DNAVMODE]
This command is used to enable or disable GNSS navigation with height constrained (2D
navigation) and set the height constraint when the receiver computes a 2D navigation solution.
Use 2D navigation mode only when the height can be constrained accurately.
Otherwise, large errors may occur in the position solution.

Upper height limit imposed due to export limitations.
Examples: [2DNAVMODE]AUTO,0.0000
Commands the receiver to automatically transition between 3D (4 satellite
minimum) and 2D (3 satellite minimum) navigation. This can also be determined by
DOP values, even if 5 satellites are available. In 2D navigation, the last valid
computed height measurement is used.
[2DNAVMODE] ALWAYS, 10.5
Commands the receiver to switch to 2D (3 satellite minimum) navigation and set 2D
height to 10.5 meters. The receiver must compute an initial 3D navigation solution
before it transitions to 2D navigation. After 2D navigation is established, the receiver
will not transition back to 3D navigation.

View the PVT tab for the current nav mode and indication of 3D or 2D navigation.