COLUMBUS, Ohio - The biggest driving force behind adopting precision agriculture technology is how quickly a farmer can recoup the investment costs of the equipment.
Ohio State University researchers, in an effort to provide information on the most accurate, cost-effective equipment on the market, have found global positioning guidance systems that not only have the potential to pay back to the user, but operate under minimal costs. Reza Ehsani, an Ohio State Extension precision agriculture state specialist and Matthew Sullivan, an Ohio State Extension program specialist, have tested six commercially available differential global positioning system (GPS) guidance systems with WAAS (Wide Area Augmentation System) differential signal. WAAS is a GPS differential source originally provided by the Federal Aviation Administration in air travel that has the abilities to calculate accurate GPS correction signals for precision agriculture. "In order for a GPS receiver to be accurate, one needs to have a differential source and there are three sources available to farmers: commercial satellite providers, Coast Guard beacon signals and a new source known as WAAS," said Ehsani. "GPS guidance systems are examples of how technology can pay back to the farmer and they are the quickest way of doing it that has been on the market so far." The researchers believe WAAS may be advantageous in precision agriculture technology for a variety of reasons. The WAAS signal can be picked up throughout the North American continent and is free to use. In addition, WAAS uses the same signal frequency as the GPS signal and many guidance systems are available that operate with WAAS. In some cases, these systems are cheaper than GPS guidance systems that are using other differential correction sources. Coast Guard beacon signals are free, but are restricted to bodies of water and become degraded as the distance increases from the source. Commercial satellite providers charge an annual fee to use their signals. "WAAS, we think at least in Ohio, is a very good differential GPS source for farmers. They can use it directly or as a backup to their current differential source" said Ehsani. "In our evaluations, we were interested to see how accurate GPS guidance systems with WAAS were and their cost-effectiveness." Based upon research conducted in central Ohio, the researchers found that, 95 percent of the time, the systems had the accuracy of staying within 20 inches of the desired position when driving in a straight line. On a typical Ohio farming operation this 20-inch error can be expressed as a two-percent overlap with a 90-foot boom width compared to a possible five-six percent overlap with traditional foam markers. "That's pretty good for farmers to conduct a variety of field work, from spraying to laying down fertilizer with a low percentage of overlap," said Sullivan. "And that three percent advantage over foam markers when spraying a 2,000 acre operation, for example, it means 60 acres less in overlap, potentially saving the farmer $900 in chemical applications at $15 an acre per year. Plus taking into consideration the time and fuel the farmer saves and the wear and tear on his tractor." In addition, the free source of differential GPS saves farmers around $800 a year in subscription costs and many companies that provide guidance systems with WAAS-only GPS receivers can save the buyer up to $1,500 compared to a GPS receiver that receives more than one type of differential frequency. The cost of guidance systems runs between $4,000 and $13,000 depending on their complexity. Before purchasing any kind of guidance system, however, farmers are urged to make their own evaluations and shop around for the system that suits them best, depending on their farming situation and what features the guidance system offers. Such factors, said the researchers, do have an influence on the performance of the equipment and its overall effectiveness in the field. Some considerations include: *The sensitivity of the guidance system. The sensitivity may affect the accuracy and stability of the visual display. A system should have different levels of sensitivity or a way to numerically change the sensitivity level of a light bar system.
*The overall experience of the operator. The overall accuracy should improve with driver practice.
*What production activities will the guidance system be used for: planting, spraying, spreading fertilizer/lime, harvesting, scouting or mapping. If the farming operation already conducts several practices where a guidance system may be of benefit, then purchasing a system will be more advantageous or economical. The use of guidance systems to plant with row crops such as corn has not been fully researched and is not recommended at this time.
*What type and how many implements or vehicles will the system be used in. This is important due to the portability of the guidance system and the system features. The mounting of the GPS and guidance display may be a factor in which system is best for the operation. Some display units are manufactured for inside the cab only where others can be used inside or out. The way the display units are mounted will also determine where they can be placed. When moving from one vehicle to another the amount of cabling may also be a factor to consider. Cables can be tied together to ease with installation, and as always the more something is done the more efficient it becomes as well. The manufacturers have configured the ports so that only one cable fits into a specific port.
*What technical support is provided and how will the software upgrade is managed between the user and manufacturer.
*The accuracy of the guidance system in relation to straight-line operations and during turning. The details of the study can be found at http://www.oardc.ohio-state.edu/fabe/precisionag/. A list of the companies that participated in the study, as well as additional precision agriculture information on guidance system components and options, their benefits and tips for purchasing a particular system can also be found on the website.