The methods of i-MAX and Virtual Reference Station are similar. Both are classed as individualized that require the rover to send an approximate position to the server. The relationship between the server and the rover for i-MAX and Virtual Reference Station are shown in Figures 3 and 4 respectively.
Both methods use unpublished algorithms to generate Network RTK corrections and are therefore non-standardized.
Server-controlled network solution
In both methods the server calculates the network solution to reduce the distance dependent errors. This means the network solution is not optimized for the rover’s position and might be limiting the RTK solution.
Use of all satellite data not maximised
Both methods generate RTK corrections that simulate single reference RTK. This limits the satellite data made available to the rover, therefore risking that in certain circumstances an RTK solution will not be possible.
Figure 3: The relationship between the server and rover using the i-MAX
Figure 4: The relationship between the server and rover using the Virtual
Point of Difference
The i-MAX and Virtual Reference Station methods are similar, but not identical. The major point of difference is that the i-MAX method generates corrections for a real reference station instead of a virtual reference station.
Traceability and Repeability
The i-MAX corrections are related back to a master station. This means that the baseline between the master station and the measured point can always be directly re-measured. Therefore, the measurements are traceable and repeatable (Fig 3).
With the Virtual Reference Station method the rover does not receive any observations related to a real reference station. This means that the baseline between the virtual reference station and the measured point cannot be directly remeasured. This violates the fundamental surveying principles of traceability and repeatability (Fig 4).
Leica i-MAX corrections are dynamically updated to follow the movement of the rover. In addition, i-MAX corrections are related back to a real reference station (the master station). This means that the resulting positions and accuracies are consistent.