Agriculture Reference
In-Depth Information
associated with the precision of automatic guidance based on RTK-GPS and the
repeatability of the same tracks after long time periods can be important too,
e.g.
:
•
no-till sowing into the inter-row strips of the previons crop
•
strip-tilling in autumn and sowing into the strips in spring
•
hoeing up to a distance of 3 cm from plant rows
•
applying chemicals in narrow bands precisely between narrow rows of plants
•
precise operations for expensive crops as
e.g.
potatoes, beets, vegetables, aspara-
gus
etc
.
Hence it may be that not only the use in traditional farming, but in addition such
special fi elds of application will defi ne the potential for modern guidance tech-
niques in the future.
4.4
Problems and Solutions on Slopes
4.4.1
Tractors and Self-Propelled Implements
The techniques that were dealt with above work well on fl at land. Yet a large portion
of the global agricultural area is sloped. This makes precise guidance more diffi cult.
Whenever soil erosion on sloped land is a problem, contour farming is essential as
a corrective, even if this implies guiding along curved lines and inaccuracies that are
associated with this (Sect.
4.1
). However, this is not the only problem with guiding
on slopes.
Generally, the GPS receiving antenna is installed on the roof of the tractor. So
this is the location for which positions are received. On the one hand, the position
on the roof allows rather unobstructed access to signals from the satellites. Yet on
the other hand, this location is some distance above the point, at which the imple-
ments for most farm operations work.
In fl at land, this vertical distance from the antenna to the control point on the soil
is no problem. But on slopes, this distance results in additional errors of georefer-
encing (Fig.
4.8
). When the antenna has a height of 3 m above the soil, 1° of side
slope causes a lateral deviation from the target point on the soil surface of 5.2 cm.
The deviation increases proportionally to the trigonometric tangent with the degrees
of side slope. With a moderate slope gradient of 10°, the deviation is 52.1 cm. This
is not trivial any more. Control algorithms that are based on the sensed slope have
to correct this error.
Contour farming implies that the driving occurs as much as possible along lines
of approximately the same elevation. With this driving pattern, therefore, the
machines are mainly tilted sideways to the direction of travel. This side slope - often
denoted as
roll
- is the main problem for which target point corrections are needed.
In a maritime climate and its drizzling rain, soil erosion is much less a problem
and hence driving on the contour not essential. But if instead of contour farming
