He Built His Own GPS System

He Built His Own GPS System MISCELLANEOUS EQUIPMENT Miscellaneous 21-1-27 When Jim Robins started shopping around for a GPS system a couple years ago, he decided they all were too limiting for his tastes. So the Blackie, Alberta, farmer/ computer technician put together his own system. The main reason I built it was because I didn't want to do all the grid sampling required by the commercial systems I looked at," says Robins, 28, who raises 1,700 acres of wheat, barley and canola with his father, Ed. The heart of Robins' system is a commercial airplane navigation computer that rests on the floor of the combine or tractor cab. It's "souped up" with a commercial GPS chip board that's accurate to within about 8 in. and a radio modem that receives a differential correction signal from a tower that covers no more than a 25-mile radius. The computer connects to a screen, featuring 15 power and function keys, that's suction-cupped to the window of the cab. The system uses custom-built software which provides real-time mapping, weed-tagging, and variable rate control. "We use it to collect yield data, weed information, soil sampling, general map-ping and variable rate application, same as other systems," he explains. "What makes it different is that the GPS it uses is accurate enough to create a 3-D elevation model. Using topographic information from the field, we can get away from intensive grid sampling. One year out with our system in your combine and you've got enough information to begin variable rate applications the following season. We do æbench-mark' sampling, averaging three samples per 80 acres, from the hill-top to middle to low areas. It allows us to vary fertilizer rates according to ælandscape positioning' on pre-defined prescription maps. "We use a two-tank Concord air seeder that's equipped with a Raven 750 electric controller. The air seeder has seed in one tank and a fertilizer blend in the other. "We've boosted profitability by using variable rates rather than blanket applications. Using a three-year equipment cost plus analysis fees, our costs were recouped in the first year, 1995. "We've tried boosting wheat and bar-ley populations by as much as 30 to 40 percent in our higher-producing areas. However, yields dropped by as much as 15 percent, either because of a dry spell in July and August or because populations were simply too high. "We plan to continue experimenting with variable seeding rates." Meantime, he's considering experimenting with varying chemical application rates from weed information he's collected with his system. Robins has geared up to sell his system for $20,000 (U.S.), less base station tower. He's sold four units and set up three towers with other companies in the last year and a-half. Contact: FARM SHOW Followup, Precision Farming Solutions, Box 97, Blackie, Alberta, Canada TO6 OJO (ph/ fax 403 684-2385).

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