Precision Decision

Aug 1, 2007 12:00 PM, By David Hest

What level of precision do yo need for your new hands-free steering lifestyle? That decision should be driven by how you plan to use your steering system, says Scott Shearer, an agricultural engineer at the University of Kentucky with extensive experience with automated steering systems.

“Ask yourself what you want to achieve with your steering system,” he advises. “For controlled traffic operations, such as strip-tillage, a real-time kinematic [RTK, the most accurate option] system may be a good choice. If you are looking to improve tillage efficiency, or replace a foam marker on a sprayer, a system offering decimeter or submeter accuracy may be a good choice.”

For general row-crop planting operations, whether your planting and harvest equipment widths match up will help determine if you need RTK accuracy or a system with less accuracy. “Marriage rows are very important when the planter and combine widths are different,” Shearer says. “For example, when harvesting corn, rows can be off 4 in. without a yield penalty.”

For drilling crops, a decimeter system is accurate enough, he adds, providing you plan for a slight overlap.

If you plan to use automated steering for successive field operations throughout the season, you will need a system with high steering accuracy for each operation.

Field terrain, soil type and general field conditions all can have a dramatic impact on the accuracy of any automated steering system, and how well implements track, in particular. “You cannot expect the implement to follow as accurately as the tractor is steered,” Shearer says.

Depending on the terrain, you can expect implement tracking to magnify tractor steering error as much as five- or tenfold, he says. Integrated implement-steering systems are designed to counter that effect.

Recommended steering system accuracy*
Field operation	RTK	Decimeter	Submeter
Strip-till/controlled traffic	X
Planting/row crop	X	X
Planting/drilled crop		X
Spraying/row crop in-season	X	X
Spraying/preplant, solid crop		X	X
Tillage		X	X
Fertilizer (broadcast)		X	X
Harvest	X	X
Source: Scott Shearer, University of Kentucky *Minimum accuracy of automated steering systems recommended for specific field operations