Mesh Protection
Beginnings of an innovation
Through a series of fortuitous incidents he was introduced to staff at Cii who conducted market research, sorted out trials, and helped with other things he had not had much experience with at the time.
Dr Rankin employs two part-time staff and Christchurch-based Assembly Specialists to manufacture the wireless Indigo units. He is also about to employ a new engineering graduate to work in the company.
The product comprises a radio unit and microprocessor in a robust IP67 tube about 30 centimetres long, powered by a next-generation nickel-metal-hydride battery, or by a solar panel. The low self-discharging batteries will last up to a year in the field before needing to be recharged.
Alongside each radio unit in the field are a number of sensors for measuring climatic variables – temperature, humidity, atmospheric pressure or wind speed for example. Other information such as the pressure of an irrigation pump can be relayed and controlled if necessary. The grower decides on the number and placement of sensors according to the particular size and geography of the vineyard. Typically, vineyards can have different areas of soil compaction and water retention that complicate the problem for growers. Variable limits are set by the grower and entered into the system for the radio units to activate alarms if they are breached. The grower can choose to control the system manually or automatically.
The radio units "nodes" are arranged in a mesh network, generally with one unit and its accompanying sensors every 2–3 hectares. The number varies according to the terrain and Dr Rankin has sites where he has installed more than one sensor per hectare and others with one every 10 hectares. He sees this versatility as one of the major advantages of his system. It is very scalable and easily configured to match any situation.
In a mesh network all the nodes talk just to their nearest neighbours and route information to an end destination. Should a node fail for some reason, the other nodes know how to bypass it and get the information through. The system automatically configures itself and this "self-healing" feature adds to the robustness of the overall network.
The nodes are usually placed on posts in the vineyard amongst the vine canopy but below the level where mechanised trimmers prune the vines. This is a compromise as dense or damp foliage could diminish the signal, but viticulturists do not want tall posts throughout their vineyards. Nodes are also put onto three-metre masts at the periphery of the vineyard and, with their longer range, can provide a "backbone" network between possibly obstructed in-vineyard sensors and radios.
