21 December 2001

Guidance system keeps on course

GPS control of farm machinery is firmly on the increase. LH Agros Swath XL guidance system provides a set of lights to tell the sprayer or fertiliser spreader operator whether he is driving on course or not.

Why would you need such a thing? Because with sprayers, cultivators and fertiliser spreaders working to ever greater widths, the danger of excessive overlapping or under-driving becomes greater. Plus you can drive at night as accurately as you would in the day, claims LHAgro.

With a 36m sprayer, for instance, an accuracy level of 1-1.5m would be considered good, says Richard Reed from LH Agro UK. The Swath XL, on the other hand, can achieve 20-30cm accuracy provided its used with a good GPS reference system.

This type of information is included on a number of GPS-based instruments, but is generally only one of several data readouts grouped on one screen. The Swath XL, by contrast, is a dedicated, physically large unit that can be sited on the tractor bonnet to allow the driver to keep his eyes on the field ahead.

The user can also calibrate the unit so the first light comes on if he strays, say 30cm off track, the second if he goes 60cm off track.

If the field is already GPS mapped, setting up the unit simply involves downloading the field grid into the Swath XL. If not mapped, spraying a field would typically involve doing the headland in the conventional way, then setting up the system along a relatively straight side.

The mapping system will then provide a series of parallel lines along which the tractor needs to drive. Price is £2500. &#42

They would be like tramlines only more accurate.

There are 300 of these units in the US, but as yet only three or four in Europe, says Mr Reed. Cost is currently £2500, assuming you already have GPS. That may sound a lot, but for large-scale farmers the payback would come from less overlapping and more scope to do night work.

The Smith XLsystem uses lights for more accurate steering.