A number of providers have turnkey options that do some or all of this automatically. John Deere’s iGrade, Ag Leader’s Intellislope, Trimble’s FieldLevel II, and the AGPS Inc suite of AGPS-Topo and AGPS-Dirt Pro are off-the-shelf tools to create terrain maps and automatically control equipment.
Laying tile drains is also much easier with GPS. Programmes such as FieldLevel and Intellislope measure elevation while the tractor drives along the proposed drain line.
Of course laser levelling has been available for decades. However, it is limited to straight lines forming a single flat plane from any base set-up. Fitting a flat plane to a curved Earth – effectively a board on a ball – creates problems.
Water runs downhill, which is down relative to the curve of the Earth (dark grey sphere – see Diagram 1. If run length is excessive the plane surface rises above the curve requiring water to run uphill (blue arrow).
An in-cab guidance computer calculates optimum grades based on minimum and maximum depth and slope then controls installation depth.
In practice drain pipe is laid alongside the planned drain and fed together with a gravel envelope into a pipe-laying shank on the machine.
The depth of the shank is automatically controlled according to the design saved in the onboard computer. Pitch control allows it to be angled, reducing stress on the machine.
It is very efficient – no prior surveying, no marking out, no trenching, and no backfilling.
A Hawke’s Bay system is capable of laying pipe at over 1km per hour. To date this is limited by the ability to keep shingle supplied.
The drain-layer has its own hopper holding enough shingle for 200m of pipe. When a towed hopper is added to the system, shingle will be supplied faster, and the work rate is likely to improve dramatically.
