Trimble Outdoors SK8 - Manual (Page 58)

4-6 Lassen-SK8 Embedded GPS Module
Operation and Performance
3D Manual
In 3D Manual mode, the Lassen-SK8 will only generate 3-dimensional (3D) position
solutions (latitude, longitude, and altitude). A 3D solution requires at least four visible
satellites which pass the mask criteria. If less than four conforming satellites are visible,
the Lassen-SK8 will suspend position data outputs. 3D Manual mode is recommended for
differential GPS applications requiring the highest level of accuracy.
2D/3D Automatic
The default operating mode for the Lassen-SK8 is 2D/3D Automatic. In this mode, the
Lassen-SK8 attempts to generate a 3-dimensional (3D) position solution, if four or more
satellites meeting the mask criteria are visible. If only three satellites are visible which
meet the mask criteria, the Lassen-SK8 will automatically switch to 2-dimensional (2D)
mode and will use the last calculated altitude, if available, or the default altitude in the
position solution. In 2D/3D Automatic mode, the PDOP switch is active.
4.5 Differential GPS Operating Modes
The default mode for the Lassen-SK8 is DGPS Automatic. The Lassen-SK8 supports
three DGPS Modes: On, Off, and Automatic, and the mode may be changed by issuing the
appropriate TSIP command. See Appendix A for information on TSIP commands. The
three DGPS operating modes are described below.
4.5.1 DGPS On
When DGPS On is selected, the Lassen-SK8 will only provide differential GPS solutions.
If the source of correction data is interrupted or becomes invalid, the Lassen-SK8 will
suspend all output of position, course and speed data. When a valid source of correction
data is restored, the Lassen-SK8 will resume outputting corrected data.
4.5.2 DGPS Off
When DGPS Off is selected, the Lassen-SK8 will not provide differential GPS solutions,
even if a valid source of correction data is supplied. In this mode, the receiver will only
supply standard GPS data.
4.5.3 DGPS Automatic
DGPS Automatic is the default operating mode for the Lassen-SK8. In this mode, the
Lassen-SK8 will provide differential GPS solutions when valid correction data is
available. If a set of differentially correctable satellites cannot be found which meets the
satellite mask settings, the receiver will transition to output standard GPS solutions. The
Lassen-SK8 automatically switches between DGPS and standard GPS based on the
availability of valid correction data.