Precision Farming: Case IH Virtual Reference Station VRS

The advance of mobile phone technology means farmers can now have RTK precision without the hefty initial capital outlay. Case IH is one of the first agricultural firms to offer this  guidance technology and demonstrates it here to profi

With farmers and contractors spreading themselves wide and far, RTK may not be the most appropriate means of achieving high-end precision guidance. So it’s just as well that there’s now another option – a Virtual Reference Station or VRS.

The kit is relatively new on the agricultural scene, but it has been employed in the construction sector for a number of years. VRS uses mobile phone technology, and CNH is one of the first firms to offer it in the UK
and Ireland after teaming up with Trimble.

Rather than relying on an RTK base station to provide the correction signal, the tractor – or any other self-propelled machine – utilises a phone-based data transfer system that connects to a VRS server. This server then generates RTK correction data as if it was coming from a local reference station. Just like the RTK system, a receiver is still required to supply the GPS element.The basic principle behind the VRS network is that reference stations (115 in the UK belonging to Ordnance Survey Great Britain and 22 privately owned in Ireland) continuously send data to a central server, which calculates area and atmospheric corrections for the region covered by the network.

The tractor’s receiver taps into this system with a mobile phone link and transmits the vehicle’s position to the server. The server uses the information to calculate the unique corrections for this vehicle position based on the six nearest reference stations, which eliminates any inaccuracies caused by the distance from the reference stations. Other country differences include Case IH opting to use Vodafone in the UK but O2 in Ireland. While VRS is available in other countries such as Germany, it is not available in France for instance.

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