Agriculture Reference
In-Depth Information
Seed
Fertilizer
Insecticide
Herbicide
Receiver location
Hitch point
FIGURE 5.2
Illustration of a machine definition for a tractor/planter combination with
multiple product metering and delivery systems using the GMM. (Adapted from Macy, T.,
Field Operations Data Model, available at: http://www.mapshots.com/ftp/FODM/FODM_
Overview.pdf 2003.)
control console, and the GPS coordinates are stored. As the operator continues to
cover the field, the automatic guidance system can be engaged, and the equipment
will attempt to follow parallel paths to cover the field based on steering sensor feed-
back and GPS data. Many systems also provide the ability to follow curved paths that
are input in much the same way.
Two basic types of automated guidance systems are typically used today by pro-
ducers. The first system consists of a steering actuator mounted to the tractor's steer-
ing wheel. The second system is integrated into the tractor's steering system and uses
a control valve to actuate the hydraulic steering cylinder directly. The overall accu-
racy of these systems relies heavily on the type of GPS technology used (RTK GPS
provides the highest accuracy) as well as proper installation and setup. Ultimately,
these systems benefit producers by reducing operator effort and pass-to-pass overlap
during field applications. Large-scale farming operations use automated guidance of
tractors and implements to increase productivity. Accurate application of crop inputs
in a timely fashion is possible with automated guidance. Most of the automated guid-
ance applications use RTK GPS, which provides sub-inch accuracy.
Automated guidance systems for agricultural tractors are being rapidly adopted
by U.S. producers as this technology leads to increased machine productivity,
extended operating hours, and reduced operator fatigue. Manufacturers of these sys-
tems advertise guidance errors within centimeters of the true path. However, pro-
ducers may be more interested in implement tracking behind the tractor. Veal et al.
(2009) developed an approach to determining cross-track error and then deployed
this approach to evaluate the effects of ground cover, ground slope, draft load,
and implement type on trailing implements. Field data collected from tractor- and
implement-mounted GPS receivers were processed to establish cross-track errors as
judged by the perpendicular deviation from the A-B line. This investigation revealed
