5 Connectivity Connectivity concepts
Accuracy
xFill technology can maintain a relatively high level of horizontal accuracy throughout the RTK
outage period. However, accuracy is primarily dependent on three factors:
l GNSS satellite availability and obstructions between the satellite and receiver (trees, buildings,
and so on)
l Exactness of the base station position
l Length of time since the last RTK position (maximum allowable time is 20 minutes)
If you are concerned with maintaining sub-inch precision, disable the xFill feature.
Estimated accuracy over time while the xFill function has been active (with base station accuracy
<20cm) is as follows:
l xFill runtime – no RTK corrections Estimated error
l 1-5 minutes 1-5cm
l 6-10 minutes 5-9cm
l 11-20 minutes 10-15cm
Dependence on satellite
xFill technology requires correction data from at least 5 satellites higher than 10 degrees from the
horizon. If GLONASS is unlocked at the RTK level, xFill technology will also be able to use GLONASS
satellites. Additionally, large objects such as trees, buildings, and grain bins will significantly
decrease or completely block signal reception from all satellite types, including GPS, GLONASS, and
corrections satellites. If these same obstructions are between the receiver and the satellite, they
may also block xFill signals.
WARNING – Many large and sudden changes in satellite geometry caused by blocked satellites can cause
significant position shifts. If operating under these conditions, auto-guidance systems can react abruptly. To avoid
possible personal injury or damage to property under these conditions, disable the auto-guidance system and take
manual control of the vehicle until conditions have cleared.
Dependence on base station position
When the RTK correction signal is lost, the RTX satellite begins providing correction based on the
last RTK position. When you setup xFill and select the datum in which you surveyed your base
station, the firmware translates your position into the ITRF datum reference frame to minimize drift.
Any other inaccuracies in the base station position can cause a drift in position over time.
As time elapses, correction data from the satellites causes drift from the RTK line. The larger the
difference in surveyed base station position, the larger the drift as shown in following table.
The following table shows how the xFill drift over time is impacted by the accuracy of the base
station survey coordinates.
134 TMX-2050 Display User Guide Version 1.075, Revision C
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