When connected to a GNSS antenna that receives a GNSS signal, VersaSync can use GNSS as an input reference. The factory default configuration allows GNSS satellites to be received/tracked with no additional user intervention required.
However, there are several user-configurable GNSS settings:
- The Receiver Mode function allows the GNSS receiver to operate in either a stationary mode (“Standard” or “Single Satellite” modes), or in a mobile mode environment e.g., in a vehicle, ship or aircraft.
- Offset [ns]: to account for antenna cable delays and other latencies
- Receiver dynamics: to optimize performance for land, sea or air operation
- The ability to delete the stored GNSS position information (latitude, longitude and antenna height).
- The option to determine when a resurvey is to be performed (supported only by newer GNSS receivers).
To configure the GNSS Receiver Mode for your VersaSync unit:
- Navigate to INTERFACES > REFERENCES: GNSS 0. The GNSS 0 Status panel will open.
- Click Edit in the bottom-left corner. The GNSS 0 configuration window will open:
- Select the desired Receiver Mode, and click Submit.
GNSS Receiver Modes
The receiver modes are:
The Standard Mode can be used only for stationary applications, i.e. the VersaSync unit will not be moved. Also, it must be able to track initially at last four satellites in order to complete the survey. (Once the survey is completed, less than four satellites will provide a valid Time and 1PPS.)
About the GNSS Survey
In the Standard Mode the so-called GNSS survey will initially be performed, once at least four GNSS satellites become available. The GNSS survey is used to determine the exact position and time; it takes 2000 seconds (33 minutes) to complete a survey. During the survey, the GNSS receiver must continue to track at least four satellites, otherwise the GNSS survey will not complete.
Upon completion of the GNSS survey the GNSS receiver will lock-in the calculated GNSS position and will enter Standard Mode. Once in Standard Mode, the GNSS survey will only be performed again if:
- the equipment will be relocated to another location and the receiver detects this (applies to most Trimble receivers)
- you manually delete the GNSS position, see Deleting the GNSS Receiver Position.
In the event that VersaSync cannot complete a GNSS survey within 24 hours (e.g., the survey progress does not go beyond 99%), see Single Satellite GNSS Receiver Mode.
The Single Satellite Mode is designed for use cases in which it is not possible for the GNSS receiver to track at least four GNSS satellites for at least 33 minutes continuously in a 12-hour time window so as to complete the GNSS survey, i.e. obtain a 3-D fix. In such cases, VersaSync cannot operate in Standard Mode. This occurs frequently in areas with limited view of the sky (e.g., "urban canyons").
In Single Satellite Mode, the GNSS receiver will be considered a valid input reference as long as:
- the receiver was able to complete a survey during a time window with good satellite reception, OR you have manually entered a valid position for your antenna location (instructions can be found under Manually Setting the GNSS Position and Determining Your Position.)
- the GNSS receiver continues to track at least one qualified satellite.
Note that VersaSync is designed to provide the most accurate time in Standard Mode, hence the Single Satellite Mode should only be used if the GNSS receiver could not complete a survey. Note also that Single Satellite Mode can only be used if the VersaSync unit remains stationary at all times.