Compensating for GPS drift

Drift may develop over time (when correction sources with a low degree of precision are used). When the operator returns to a field, there may be a slight difference in the vehicle position indicated relative to fixed objects such as the boundaries of the field or the guidelines. This is primarily due to differences in the GPS satellite constellation.

Drift may also be caused by other factors such as an obstructed view of the sky (when in the vicinity of trees or other obstacles) and satellite data errors.

Note: As the vehicle may also be repositioned on a selected flag point.

To compensate for GPS drift:

1. Select: / Nudge Menu / GPS drift compensation.

The compensation value may be selected by: entering a positive or negative value in the NORTH and/or EAST field and confirming;

or

by entering the required value in the GPS DRIFT INCREMENT field and then pressing the required direction button repeatedly until the desired drift compensation value is reached.

2. Select Reset GPS drift to cancel the selected GPS drift compensation.

GPS drift correction

When GPS drift is active, the position of the vehicle on the map is offset relative to other objects (e.g. the boundaries of the field, the guidelines, the flag points and any previously plotted coverage). The simplest way to view the correction as it is applied on the map is to select the 'North up' view and then pan the map until the vehicle appears next to the GPS Drift Options menu.

To compensate correctly for GPS drift:

1. Drive the vehicle to an easily identifiable location in the field (e.g., next to a gate, in a corner of the field or in the wheel furrows left from the previous year).
2. Use the functions in the GPS Drift Options menu to move the position of the vehicle on the map into the correct position relative to the fixed reference point or points.

To make this procedure quicker and more precise, it may be helpful to set a flag point in the reference position in the field. Each time you return to the field, drive to the reference position, place a flag point on the map in the reference position and select it. This opens a window with the option "GPS drift correction". Select this option to move the displayed position of the vehicle to the flag point.

The GPS drift compensation applied is retained when the console is switched off and on again. However, the compensation may no longer be accurate if conditions have changed. When the system is switched on, an alarm message is displayed briefly notifying the operator that GPS drift compensation is active. The operator must decide if they want to continue using this compensation factor, cancel it or perform the GPS drift compensation procedure again to obtain more accurate results for the new session.

High precision correction sources

GPS drift compensation is not necessary if high precision correction sources are used (e.g. RTK). If a high precision compensation source is used, GPS drift compensation must be cancelled in the GPS Drift Options window.