It's all very well setting up virtual guidelines for a tractor's visual guidance or automatic steering system to follow, but what if the implement being used doesn't run true?

After all, a large part of the justification for GPS autosteer is its ability to maximise implement output by minimising overlaps and allowing accurate work to continue at night. With ultra-accurate 1 INCH (±2cm) RTK system accuracy measured in the INCH/low centimetres, equipment that runs off-centre creates a headache.

"Once you've got a highly accurate RTK guidance system on the tractor, you come to realise how poorly a lot of implements follow, even on flat ground," says Paul Smith, Precision Expert at Northern Equipment Solutions.

Speaking at a precision farming workshop that helped growers adopt a "controlled traffic" approach to field operations, Mr Smith cited difficulties keeping equipment on track when preparing land for cash crops and potatoes.

With the latter, auto-steering achieves tight bed spacing but if things go out of true the tractor's front wheels can end up running over a row trying to compensate.

It is suggested to adopt GPS Steering to solve these issues and identify two common causes of implement misalignment.

For most growers, this problem relates to gravity pulling an implement downhill as it works across a slope.  This can be corrected using 'passive' implement steering, where you have a receiver on the implement to help control the tractor's steering, or by attaching a Protrakker system that steers the implement at the hitching point to the tractor, when the implement does not have the option of “active” implement steering, implements that come equipped with steering can be steered actively.

Among the systems commercially available are Trimble's TrueGuide and the John Deere iGuide system, both of which provide "passive" steering correction to keep heavy cultivation and seeding implements on track as they traverse hills and hollows.  Systems commercially available for active systems are Trimble’s TrueTracker and The John Deere iSteer Systems, both of which control the implements steering system to place the implement in the correct position at all times.  Implements looking for the increased accuracy of active style steering can provide steering by directing the tongue of the implement to correct the position.

GPS-steered or Giro Operated ProTRAKKER by MBR

In passive guided systems, these add-ons use the existing terminal of the tractor's auto-steering system with a receiver mounted on the implement. Extra software calculates the steering inputs needed to offset the tractor uphill so that the implement follows the correct path to neatly butt up to the previous pass, with the overlap pre-set by the operator and no gaps.  Whereas active systems steer the implement independently of the tractor, much like having 2 independent GPS systems.

It's a step beyond the implement compensation feature that most auto-steering systems now have and which take into account the way a trailed implement cuts corners. They work by calculating the implement's path from the position of the drawbar pivot and working elements - such as the coulters on a drill - relative to the receiver to cause the tractor to steer a little wider through a curve than it would otherwise.

With TrueGuide and iGuide, the receiver on the implement provides the main guide reference, with RTK signal correction giving ±1”/±2cm accuracy. The tractor then compensates for implement crabbing on slopes, as well as accurately compensating through curves based on the actual path of the implement.

Suppliers say the technology brings to undulating and hilly ground all the benefits of accurate bout matching and tramline positioning that are easily achieved on level fields.

However, the 'passive' steering approach may not be enough for a wide implement that tends to pull to one side or the other inconsistently. The level of consistent accuracy will not be enough in situations where you want the implement to consistently follow a very precise path.

This level of implement control accuracy has other potential uses. Such as strip tilling and placement of slurry and/or fertiliser along crop rows before they are sown - an approach that lends itself to a controlled traffic situation using the same wheel paths year after year.

WHAT EQUIPMENT IS OUT THERE?

Trimble

Trimble says its AgGPS TrueTracker package is designed to handle a number of different implement steering solutions, including on-the-move hydraulic drawbar adjustment, steerable implement support wheels and rudder discs, as well as side-shift and yaw adjustment on mounted equipment.  Trimble’s Trueguide package is designed to use calculations from a implement mounted controller to guide the tractor to correct the path of the implement.

As well as the implement-mounted antenna, the system includes the NavController II controller with terrain correction to compensate for the antenna's offset position caused when the implement is working across a significant incline.

John Deere

John Deere says its Starfire GPS iSteer  package is designed to handle a number of different implement steering solutions as well, including on-the-move hydraulic drawbar adjustment, steerable implement support wheels and rudder type discs, as well as side-shift and yaw adjustment on mounted equipment.  John Deere’s iGuide package is designed to use calculations from a implement mounted controller to guide the tractor to correct the path of the implement.

As well as the implement-mounted antenna, the system includes the iSteer controller to compensate for the antenna's offset position caused when the implement is working across a significant incline.

Protrakker

MBR maker of the Protrakker says its tongue guidance package is designed to control non-controllable implement types including pull type sprayers, tillage and cultivators, any type of planting equipment and veggie harvester .  MBR’s Protrakker can be controlled with MBR Giro based controller, or with either Trimble’s TrueTracker or John Deere’s iSteer.

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Paul Smith is the owner of Northern Equipment Solutions and based in Central Ontario, Canada. Providing Quality Potato Equipment, Precision Agriculture and Other Advanced Equipment, Northern Equipment Solutions ensures that your profits and yields are maximized. www.northernequipment.ca or sales@northernequipment.ca